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Effects of two species of VA mycorrhizal fungi on drought tolerance of winter wheat. New Phytol 93: 67-76
New Phytologist
Abstract
S ummary
Roots and soils from western Nebraska fields of native and planted grasslands, and winter wheat of varied fallow‐wheat cultivation duration, were evaluated for vesicular–arbuscular (VA) mycorrhizal root infection and spore numbers and types. Increased cultivation decreased percentage mycorrhizal infection in wheat and reduced spore numbers of Glomus fasciculatus , the dominant VA mycorrhizal fungus in these soils. Spore numbers of other VA mycorrhizal fungi did not change significantly with cultivation although mean numbers of G. mosseae increased with continued wheat production. Water relations and growth were determined for greenhouse‐grown non‐raycorrhizal, G. fasciculatus ‐infected, and G. mosseae ‐infected wheat in wet and dry soils. Stomatal conductances were higher in mycorrhizal than in non‐mycorrhizal plants in both wet and dry treatments. Stomatal closure in‐mycorrhizal plants occurred at lower leaf water potentials (Ψ 1 ) and after greater desiccation than in non‐mycorrhizal plants, but some leaves of G. mosseae‐infected plants showed no stomatal response to drought and continued to transpire at Ψ as low as ‐4.1 MPa. Leaf osmotic adjustment was greatest for G. fasciculatus ‐infected plants. Non‐mycorrhizal and G. fasciculatus‐infected plants had equal dry wts in both wet and dry conditions. Infection by G. fasciculatus appeared to increase wheat drought tolerance while infection by G. mosseae did not.
... Colonization by mycorrhizae can occur either intracellularly (arbuscular mycorrhizal fungi) or extracellularly (ectomycorrhizal fungi). These microorganisms play integral roles in the intake of important nutrients such as phosphorus (Bolan, 1990), and may have positive effects on host plant growth (Allen et al., 1983) and response to environmental stressors, such as drought (Allen et al., 1983;Ruiz-Lozano et al., 1995). ...
... Colonization by mycorrhizae can occur either intracellularly (arbuscular mycorrhizal fungi) or extracellularly (ectomycorrhizal fungi). These microorganisms play integral roles in the intake of important nutrients such as phosphorus (Bolan, 1990), and may have positive effects on host plant growth (Allen et al., 1983) and response to environmental stressors, such as drought (Allen et al., 1983;Ruiz-Lozano et al., 1995). ...
... Thus, mycorrhizal fungi may play an important role in increasing a host plant's response to drought conditions by affecting water intake and increasing efficiency of nutrient uptake. Allen et al. (1983) showed that colonization of winter wheat by arbuscular mycorrhizal fungi caused stomata to close at a lower water potential than non-colonized winter wheat when exposed to drought conditions. Ruiz-Lozano et al. (1994) showed that colonization of lettuce by seven different arbuscular mycorrhizal fungi showed significant positive effects on post-drought shoot dry biomass, root dry biomass, and the root/shoot ratio. ...
Endophytic fungi asymptomatically colonize the internal tissues of plants. Endophytes are components of the plant tissue microbiome and can increase host plant growth and tolerance to environmental stressors, such as drought. We isolated an endophyte complex (LG2) from the fruit of Capsicum annuum pepper plants and identified it as a member of the genus Colletotrichum. We identified two morphotypes within this endophyte: LG2G and LG2O. Anecdotal evidence suggested that treatment of Antohi Romanian pepper seeds with this endophyte complex might have positive effects on seedling growth and drought response. In this thesis, we examined the effects of the LG2 endophyte complex and the individual morphotypes of LG2 on C. annuum growth and drought response. We found that seed treatments where the two morphotypes grew together significantly increased seedling biomass and increased the number of days to wilt when under drought conditions. However, seeds treated with separately grown morphotypes did not have any significant effects on seedling biomass or drought response. These findings suggest that the LG2O and LG2G morphotypes work synergistically in order to affect the production phytohormones or secondary metabolites crucial for plant growth, development, and responses to abiotic factors such as drought. Understanding interactions between multiple endophyte morphotypes and how these interactions affect their host plants could help us to better understand how host plant distributions might be altered as global temperatures continue to rise and drought conditions become more widespread.
... under drought conditions (Hetrick et al., 1987). In addition, the drought resistance of wheat plants grown in pots was dependent on the type of AMF used, where colonization by Glomus fasciculatus increased drought resistance, while colonization by G. mosseae did not (Allen and Boosalis, 1983). Therefore, when endeavoring to understand the impact of AMF on plant responses to drought and when making comparisons among studies, it is important to consider the type of plant and AMF used, the severity and duration of the drought stress experienced by the plant, and the type of experiment (i.e., pot or field). ...
... Moreover, AM colonization of field-grown wheat (Ryan and Ash, 1996) and pot-grown maize (Hetrick et al., 1987) was low under severe drought. According to Allen and Boosalis (1983), the P-uptake response of wheat grown in pots depends on the species of AMF used. These contrasting results among plant species, and across experiments, might be due to the time at which measurements were taken, the plant growth stage at which the drought was imposed, and the severity and duration of the drought treatment (Table 4.1). ...
... When considering osmotic adjustment of AM plants, again, conflicting results are reported. Henderson and Davies (1990), Davies et al. (1993), Goicoechea et al. (1997), and Duniway (1997, 1998) concluded that drought resistance of AM plants was not due to osmotic adjustment, while others concluded the opposite (Allen and Boosalis, 1983;Augé et al., 1986Augé et al., , 1987. The absence of osmotic adjustment in AM plants is apparently due to the development of another type of drought response. ...
... Wedagama et al. [13] found that increasing water stress by reducing soil moisture content from 70% to 40% of field capacity causes the percentage increase number of indigenous endomycorrhizal spores taken from salak roots to be higher. Allen et al. [14] and Wu and Zou [15] obtained number of mycorrhizal spores increased significantly with reduced rainfall or increased soil dryness. The higher presence of spores in the dry season is related to plant phenology [16]. ...
... The abundance and activity of mycorrhizae on plant roots is largely determined by environmental factors, especially drought [4,[20][21][22][23], and mycorrhizal species [24][25][26]. Fertile soil with sufficient water content reduces root colonization by mycorrhizae, whereas drought causes the level of root colonization and the effectiveness of P, N and K nutrient uptake by mycorrhizae increase [14,[21][22][27][28][29]. Leal et al. [30] reported that the number of endomycorrhizal spores of the genus Glomus and Acaulospora in drought-affected Eucalyptus camaldulensis plants increased more than 300 times compared to plants grown on sufficient water content, but the increase in the number of spores of the endomycorrhizal genus Scutelospra was significantly lower, while Mathimaran et al. [31] found that moderate drought level caused root colonization by arbuscular mycorrhizal increase sharply with an increase in root range of up to 80%, but at severe drought level plant growth was inhibited and mycorrhizal colonization ability also decreased significantly. ...
Biofertilizer with Arbuscular Mycorrhizal Fungi (AMF) as the inoculants is needed in organic cocoa cultivation on smallholder plantations in Indonesia. AMF biofertilizer requires a sufficient number of spore inoculants, so it is necessary to multiply isolated spores. Research objective was determining the effect of water stress and mixed types of AMF genus from cocoa roots on spore propagation and root colonization used corn as the host plant. The study used a 2-factors randomized block design and 3 replications. The first factor was water stress consisting of 3 levels (without water stress as a control, soil moisture content 100% of field capacity; light water stress, soil moisture content 70% of field capacity; and heavy water stress, soil moisture content 40% of field capacity), while the second factor was mixed types of AMF genus also consisting of 3 levels (inoculant of genus Glomus only, mixed inoculants of the genus Glomus + Acaulospora, and mixed inoculants of the genus Glomus + Scutelospora. Result of research showed, the interaction of water stress and mixed types of the AMF genus had no significantly affect on the number of spores reproduced, root colonization and host plant growth. The best way of propagation of AMF spores was by heavy water stress treatment with a soil moisture content of 40% of field capacity producing 6,713.40 spores or an increase of 13,326.82%. Mixed inoculants of the genus Glomus + Scutelospora gave the highest number of spores after propagation (6,263.40 pieces) or an increase of 12,427.77%.
... The growth of mycorrhizal treated plants was greater than non-treated ones. The increased growth was attributed to increased stomatal conductance (Allen and Boosalis, 1983) and root conductivity (Graham and Syvertsen, 1984) provided by increased surface area of mycorrhizal hyphae (Hardie andLeyton, 1981 andAllen, 1982). These reported changes could be secondary responses to better P nutrition (Nelsen and Safir, 1982;Michelsen andRosendahel, 1990 andOsonubi et al. 1990) or mediated via direct mycorrhizal effects (Henderson and Davies, 1990). ...
... The positive effect of soil inoculation may due to the VA mycorrhizal fungi is known to increase N uptake, particularly P and biomass accumulation of many plant species in low P soil (Nelson and Safir, 1982). The increased growth was attributed to increased stomatal conductance (Allen and Boosalis, 1983). ...
... Acidic soil conditions increase the availability of potentially toxic metals, which makes it even more challenging for organisms to survive and reproduce in these areas (Danielson and Visser 1989). Mycorrhizal fungi contribute to the degradation of man-made xenobiotic compounds by the process rhizodegradation so that plants absorb such compounds from roots to aerial parts by the process phytoextraction before releasing these toxic elements to the atmosphere as remedy for environment pollution (Allen and Boosalis 1983). Drought is one of the plant stresses which affects growth and development of many plants, but there are some plants species that are drought resistant. ...
... This is because of the aggregating outcome of mycorrhizal hyphae on soil structure (Augé et al. 2001). Also hyphae can enter pores that are too small for root hairs to access and hyphae proliferated well beyond the limit of root hairs giving plants access to more water (Allen and Boosalis 1983). Abstract Large-scale industrialization and anthropogenic activities have led inordinate disposal of waste water into fresh water bodies, causing imbalance in aquatic ecosystem and degradation of water quality. ...
In the current scenario, the world is facing various water-related issues, for instance, water shortage, degradation of water resources, pollution of aquatic systems, and proliferation of waterborne diseases. Moreover, the condition is getting worse in the developing economies because of the integrated effect of anthropogenic activities, escalating demand of resources, and the population explosion. In various developed countries, traditional centralized sewage treatment systems were used for combating water pollution. With the advancement of technologies, wastewater treatment (WWT) systems like activated sludge process, membrane separation, membrane bioreactors, etc. are being employed for treatment of water pollution. However, these expensive systems are not feasible enough for the widespread application along with they are not capable to treat water according to WWT standards. Thus, it is imperative to shift toward the natural way of water purification. In order to meet this demand, protection, restoration, and sustainable use of natural wetlands are essential because of being big reservoir of water on the earth. The present chapter comprehensively describes the importance of natural and artificial wetland (constructed wetland) for human beings toward achieving sustainable environment in a simple, manageable, and cost-effective way.
... German forest pathologist Frank (1885) coined the term mycorrhiza. Mycorrhiza word is derived from two words, one Greek mykes (mushroom/fungus) and other Latin rhiza (roots) literally meaning fungus roots (Allen 1991). Kamienski (1881) reported for the first time that root fungi play important role in growth of plants. ...
... Kamienski (1881) reported for the first time that root fungi play important role in growth of plants. In the mycorrhizal literature, the term symbiosis is used to describe a highly interdependent mycorrhizal obligatory symbiosis; the host plant receives mineral, while the fungus obtains carbon atoms from the photosynthetic plant (Harley and Smith 1983;Allen 1991). Mycorrhizal associations involve three- way communication between mutualistic fungi, host plants and soil factors, and recently arbuscular or ectomycorrhizal helping bacteria strains are reported to pro- mote this association (Garbaye 1994; Barea et al. 2002;Johansson et al. 2004;Artursson et al. 2006;Duponnois 2006;Frey-Klett et al. 2007;Rigamonte et al. 2010). ...
Arbuscular mycorrhizal fungi (AMF) have obligatory symbiotic relationship with more than 80% of terrestrial plant species. AMF symbiosis acclimatizes plants for their better survival, enhanced growth and development in biotic as well abiotic environment, thereby promoting sustainable growth and development of plants. Being highly competitive and better suited, plants with AMF association with ease tolerate environmental stress to face plethora of various biotic as well as abiotic changes. These fungal symbionts offer an eco-friendly biological sound substitute to chemical fertilizers and pesticides for managing both plant quality and quantity in agriculture, horticulture and forestry. AMF are now regarded as the cornerstone of sustainable agriculture; as such, there is a necessity to accelerate their integration in agricultural production systems. It becomes important now that soil scientists and agriculturalists pay due attention to the management of AMF in the formal way to increase, restore or maintain soil fertility which indirectly influences the growth and development of plant. Present review emphasizes the mycorrhizal symbiosis as a keystone to plant productivity and diversity because of their influence on almost all metabolic processes of plants and maintains and, in many cases, stimulates plant growth and development due to their diverse functionality/benefits to host plant, consolidated here.
... Mycorrhizal colonization improves the physiological performance of stressed plants, leading to increased yield and quality. Tolerance can be induced through differential uptake of ions present in the circulating solution, improved balance of mineral intake, effects on host plant hormonal balance, or increased water intake.Plant water relationshipMost research on AM fungi has focused on their effects on plant mineral nutrition, but there is also increasing interest in drought tolerance in mycorrhizal plants(Allen and Boosalis, 1983; Chandra et al. 2021). AM fungi are important for sustainable plant growth because they improve plant water relations and increase drought tolerance of host plants(Nelsen, 1987).Improvements in plant water status and changes in water status have been attributed to a variety of mechanisms, including those not directly related to phosphorus nutrition or water uptake (Davies et al. 1992). ...
Mycorrhiza is a symbiotic relationship between fungi and plant roots. This association of most plants with arbuscular mycorrhizal (AM) fungi plays a crucial role in many microbiological and ecological processes. In mycorrhizal association, the fungal partner allows the host plant to take up not only phosphorus (P) and nitrogen (N), but also some of the relatively immobile trace elements such as zinc (Zn), copper (Cu), and iron (Fe). AM fungi are also involved in increasing water intake, plant resistance and biological control of plant pathogens, adaptation to various environmental stresses such as drought, heat, salinity and heavy metal exposure, production of growth hormones and certain enzymes. Establishment of symbiotic relationships typically requires mutual recognition and a high degree of coordination at the morphological and physiological levels, which requires ongoing cellular and molecular interactions between both partners. This review examines mycorrhizae, their relevance, symbiotic processes in plants, as well as the role of AM fungi in water uptake, reduction of various abiotic soil stresses, protection from disease, , and increased plant susceptibility.
... Thus, they contribute significantly to crop productivity along with ecosystem sustainability in developing novel strategies of plant production and are important for managing the agricultural ecosystems in a sustainable way 4,10,13,38 . A total of 8 VAM fungi namely Acaulospora, Entrophospora, Gigaspora, Glomus, Sclerocystis, Archaeospora, Paraglomus and Sclerocystis are recognized that are responsible for the mycorrhizal association with a variety of plants and a single isolate can colonize different plants and thus showing ecological specificity 2,20,23 . With their exceptional ability to increase the phosphorus (P) uptake by plants, mycorrhizal fungi may act as a potential substitute for phosphatic fertilizers 38 . ...
The Vesicular-Arbuscular Mycorrhiza (VAM) plays an integral role in agricultural sustainability by increasing the growth and productivity of plants. During the present study, the diversity of VAM fungi was studied in the rhizosphere of 17 medicinal plant species and the parameters, percent root colonization, spore number and diversity of VAM spores associated with the rhizosphere of medicinal plants were calculated. All the selected species were found to be mycorrhizal with varying degrees of species richness. A total of 62 morphotypes belonging to 4 genera, Glomus, Acaulospora, Sclerocystis and Gigaspora were found along with 2 unidentified genera. The spore number varied from 28.6 ± 9.864 to 326 ± 78.747 spores per 50g of soil. Percent root colonization ranged from 16.6% to 84.3% with maximum colonization in Barleria cristata L. and minimum colonization in Annona squamosa L. The genus Glomus was dominant with 32 species followed by Acaulospora (12), Gigaspora (9) and Sclerocystis (8).
... AMF are known to improve drought tolerance in grapevines (Augé 2001). This can be attributed to the contribution of hyphae which absorb water more efficiently (Hardie and Leyton 1981;Sieverding 1981), favored by a better soil-root contact (Reid 1978), a greater stimulation of gas exchange through an increase in root penetration force (Allen et al. 1981;Snellgrove et al. 1982), and the effects on the adjustment of the osmotic potential (Ψ) inside the host plant (Allen and Boosalis 1983). In vines colonized by AMF, improved performances in the early stages of the implantation reduce transplant stress, thus increasing the chances of survival for the cuttings (Trouvelot et al. 2015;Van Rooyen et al. 2004). ...
Aims
Climate change imposes adaptation of viticulture in risk areas, such as the Mediterranean. Mycorrhization is a valid tool to reduce the impact of the expected temperature/drought increase. Aim of this work was to test the effects of mycorrhization on grapevine vegetative growth, element composition of soil/leaves, and microbiota of bulk soil/rhizosphere/endorhiza, in the field, under exacerbated summer stress conditions obtained by planting the rootstocks in June.
Methods
118 rooted cuttings of 1103-Paulsen (Vitis berlandieri × Vitis rupestris) were planted in Salento (Apulia, Southern Italy); about half of them were mycorrhized. Leaf Area Index, shoot growth and survival rate were monitored across two growing seasons. Leaf/shoot weight, chemical analysis of 25 elements, and 16S rRNA gene metabarcoding of bulk soil/rhizosphere/endorhiza were performed on subsamples.
Results
Mycorrhized plants showed significantly higher survival rate and growth, and accumulated significantly higher amounts of 18 elements. 27 endorhizal OTUs (representing ~20% of total sequences) were differently distributed (20 OTUs more abundant in mycorrhized plants); in the rhizosphere, instead, 12 OTUs (~2.5% of total sequences) were differently distributed. A few Actinobacterial OTUs were enriched by mycorrhization in the root endosphere; the same OTUs were the most correlated with the chemical elements, suggesting a role in element dynamics. These OTUs were not hub taxa of the co-occurrence network.
Conclusions
This work shed light onto the interactions between mycorrhiza and microbiome, in the context of plant element dynamics, which is useful to identify potential target candidates for biotechnological applications, thus moving towards a more sustainable, ecosystem-based viticulture.
... It was also shown that chickpea soil-root-microbe interaction may play a significant role in drought tolerance of chickpea (Rabbi et al., 2018b(Rabbi et al., , 2021. In water stress conditions, the abundance of mycorrhizal fungi and plant growth promoting bacteria in the rhizosphere has potential to alter water availability either by changing root architecture or by producing extracellular polysaccharides (Allen and Boosalis, 1983;Begum et al., 2019;Naylor and Coleman-Derr, 2018;Ortiz et al., 2015). The extracellular polysaccharides either from root or microbial source can retain water at low soil matric potential and thus modify the hydraulic properties of the rhizosheath (Benard et al., 2019;Czarnes et al., 2000;McCully, 1999;Read et al., 1999;Young, 1995). ...
The development of crops better adapted to endure weather extremes requires knowledge of the belowground traits that have potential to improve plant water uptake. Recent evidence has indicated that root induced modification of soil pore geometry of the rhizosheath is linked with drought tolerance of crops. Here we sought to understand whether the regulation of plant water uptake by rhizosheath is mediated through the rhizodeposits present at the soil-root interface. We compared eight wheat cultivars and demonstrated that cultivars with longer root hairs and greater rhizosheath mass and cover transpired more water. The wheat cultivars with less rhizosheath had the highest concentration of trehalose in the rhizosheath. Trehalose may increase the surface tension of soil water, which could further modify the transpiration of cultivars with less rhizosheath. Moreover, rhizosheath mass and cover had significant negative association with the bacterial abundance, indicating a link between metabolite concentration and bacterial abundance in the rhizosheath. We propose that the complex interactions of root, microbes and rhizodeposits in the rhizosheath have the potential to regulate water uptake by crops. The root and rhizosheath traits highlighted here can be targeted to develop crops with better ability to uptake water.
... These PSF effects can be negative, neutral or positive, depending on the net effect of antagonistic and mutualistic soil biota on their host plant (Bever et al., 1997). AMF are thought to contribute to positive PSF, because they can increase plant nutrient acquisition (Aerts, 2002;Read & Perez-Moreno, 2003), increase stress resistance to drought (Allen & Boosalis, 1983), and reduce susceptibility to root pathogens (Harrier & Watson, 2004;Wehner et al., 2011). However, experiments with seedlings in plant communities demonstrate that the presence of AMF does not necessarily lead to increased seedling biomass (Moora & Zobel, 1996;Koziol & Bever, 2019). ...
Establishment and growth of grassland plant species is generally promoted by arbuscular mycorrhizal fungi (AMF) when grown in isolation. However, in grassland communities AMF form networks that may connect individual plants of different ages within and between species. Here, we use an ingrowth core approach to examine how mycorrhizal networks influences performance of seedlings in grasslands.
We selected four grass and four forb species with known negative or neutral‐positive plant–soil feedback and grew them individually in steel mesh cores filled with living field soil. Cores were placed in six restored grasslands, three grasslands were of relatively young and three were of older successional age.
Ingrowing mycorrhizal fungal hyphae were severed twice a week in half of all cores, which resulted into reduced AMF colonization and increased seedling biomass, irrespective of the fields' succession stage, and the plants' grass/forb group, or plant–soil feedback type. In the control cores, root colonization by AMF was negatively correlated to seedling biomass, whereas there was no such relationships in the cores that had been lifted.
We conclude that connections to arbuscular mycorrhizal networks of surrounding plants had a negative impact on biomass of establishing forb and grass seedlings.
... Arbuscular mycorrhizal (AM) mycological association is commonly understood that it guards multitude plants from harmful properties of water stress (Auge, 2001;Abdel-Fattah et al., 2002;Ruiz-Lozano, 2003;Asrar and Elhindi, 2011). Potential apparatuses for humanizing water stress fighting of the AM plants may probably be owed toward an amplified in root hydraulic conductivity (Robert et al., 2008), stomatal guideline or transpiration rate (Allen and Boosalis, 1983), enriched aquatic commitment at low soil moisture levels as a result of extra radical hyphae (Fagbola et al., 2001), osmotic alteration which encourages turgor conservation level at low material water prospective (Auge, et al., 1986), improved photosynthetic movement, proline and carbohydrate gathering, and improved nutritive status in AMF plants (Scheilenbaum, et al., 1999). These apparatuses might be imperative in revision of the AMF plants to deficiency circumstances. ...
This study was planned to enhance the growth and productivity of common bean plants (Phaseolus vulgaris L.) grown beneath different water stress level by using different microorganisms as bio-fertilizer agents. Water stress is a international problem that effects on morphological, functional and chemical processes of plants occasioning in altering growth, yield and water relations of economic plants like common bean plants. The interaction effect between water stress (WW as recommended irrigation after 6 days, WS1 after 12 days and WS2 after 18 days) and inoculation with different microorganisms [AMF (Glomus mosseae) and endophytic bacteria, (Bacillus amyloliquefaciens)] used alone or in mixed was examined on the development and productivity of common bean plants. Mutual application of AMF and endophytic bacteria significantly increased the average values of most of growth, water relations (photosynthetic rate, transpiration rate and stomatal conductance) and yield parameters of common bean plants grown at WS1 and WS2 comparing with non-colonized plants. In this connection, colonization with AMF and endophytic bacteria with WS1 are the greater pods number, pod length, pods weight, 100 seeds weight, Yield by ton /Fed and water-use efficiency (WUE) by ton/ m³ than other treatments. Common bean yielded seeds had significantly increased nutrients content (nitrogen, potassium, phosphorus, magnesium and calcium), vitamin B1, Folic acid, crude protein and crude fibers at AMF + endophytic bacteria under second water stress (WS1) when compared to other treatments.
... This fungal partner of symbiotic association belonging to glomeromycota that corresponds to eight different genera such as Acaulospora, Archaeospora, Entrophospora, Gigaspora, Glomus, Paraglomus, Sclerocystis and Scutellospora (Morton and Redecker, 2001). These genera form symbiosis with variety of plant varying from bryophytes to angiosperms and even single isolate can colonize variety of plants showing ecological specificity (Allen and Boosalis, 1983).Numerous ecophysiological studies have confirmed importance of AM symbiosis in the soil-plant interface, such as improving plant nutrition by better nutrient and water uptake, production of phytohormones, abiotic and biotic stress tolerance. Moreover, symbiosis is also helpful to improve soil structure by production of glomalin that bind small soil particles to form large aggregates. ...
The present investigation was focused on enumeration of medicinal potential of weeds and biodiversity of Arbuscular mycorrhizal fungi (AMF) associated with them. For AMF analysis, fourteen medicinal weeds were selected, roots and their respective rhizosphereic soil samples collected from different localities of Hamirpur district, Himachal Pradesh. The results revealed that number of AM spores in the rhizosphere of plant was not correlated to percent of AM root colonization. The highest percentage of root colonization was reported in Solanum nigrum (73.54±07.15 %) and minimum in Ageratum conyzoides (22.22±00.55 %). AM spore count was recorded maximum in rhizosperic soil sample of Parthenium hysterophorus (135.32±06.05 spores per unit 50g soil) and minimum (32.26±04.10 spores per unit 50g soil) in Fumaria officinalis. Twenty five AM species belonging to four genera i.e. Acaulospora, Entrophospora, Gigaspora and Glomus were isolated during course of study. Calotropis procera preserve maximum AM spore richness in their rhizospheric soil followed by Solanum nigrum and least in Amaranthus viridis. Among variety of spores, G. geosporum is most frequently occurred species in studied soil samples. The study confirmed the weeds potential to provide hostile environment for conservation, sporulation and propagation of competent AM spores to ensure their ubiquitous distribution.
... Soil erosions degrade soil structure, decrease soil fertility, and reduce the number of microorganism, including vesiculararbuscular mycorrhizal fungi. Allen and Boosalis (1983) showed that mycorrhizal fungi population decreased under fallow rotation compared to grassland. Kruckelmman (1975) showed that tilling by rotary hoe tended to decrease spore number of mycorrhizal fungi. ...
Pengaruh kombinasi sistem olah tanah dan varietas terhadap populasi mikorisa. Suatu penelitian telah dilakukan untuk mengetahui pengaruh kombinasi sistem olah tanah dan varietas terhadap populasi mikorisa. Penelitian terdiri atas empat perlakuan yang disusun dalam rancangan acak kelompok. Perlakuan tersebut adalah varietas RR ditanam pada sistem olah tanah konservasi (RRCT), varietas C7 ditanam pada sistem olah tanah konservasi (C7CT), varietas C7 ditanam pada sistem olah tanah sempurna (C7FT), dan varietas Bisma ditanam pada sistem olah tanah sempurna (Bisma FT). Hasil penelitian menunjukkan bahwa pada pengamatan pertama C7FT secara nyata menurunkan populasi mikorisa dibandingkan dengan Bisma FT. Pengamatan kedua, sistem olah tanah dan varietas tidak berpengaruh terhadap populasi mikorisa. Pada pengamatan ketiga menunjukkan bahwa RRCT secara nyata dapat menurunkan populasi mikorisa dibandingkan dengan Bisma FT.
... The beneficial effects of VAM fungi have also been reported in the drought and saline conditions. The important feature is that in drought conditions a mycorrhizal root has ability to get additional water sources unavailable to non-mycorrhizal plant roots (Allen and Boosalis, 1983) [1] . Analytical and physiological studies have revealed that mycorrhizal plants show some beneficial effects viz., increased rate of respiration, photosynthesis and higher levels of sugar, amino acids, RNA etc and large or more number of chloroplasts, mitochondria, xylem vessels, motor cells (Hayman,1983) [9] . ...
The increasing impact of agricultural practices on environment in the world have progressively affected the soil quality in both cases i.e soil structure as well as soil biological balance, which requires the advancement of substitution of practices to minimize and lessen those impacts, parallel to the improvement on yield per cultivated area and economic benefits for producers and farmers. In addition to this, the quantity of foodstuff that today’s society require for processing and supply of the industry has encouraged the standard of new options for agricultural practices, tending to be: i) Less invasive to environment ii) Cost effective than conventional methods iii) Enhanced efficiency at low costs iv) Better quality of harvests and v) Simplified use of implements with no undue technical needs. Consequently, a technology i.e biofertilization came into existence so as to curtail environmental impacts and take full advantage of the available resources. Biofertilizers have clear-cut benefits over chemical inputs. Chemical fertilizers supply N, P, K whereas bio-fertilizers provide besides N,P,K certain growth promoting substances like hormones, vitamins, amino-acids, etc. Bio-fertilizers are well-known as a substitute to chemical inputs to augment soil fertility and crop production in sustainable farming. The application of bio-fertilizers efficiently enriches the soil and costs not more than chemical fertilizers, which harm the environment as well as exhaust non-renewable energy sources. The application of chemical nitrogen and phosphorus fertilizers at higher levels leads to accumulation of NH4+, NO3-, NO2-, PO4- in vegetable product tissues. Therefore clean agriculture recently depends upon using biofertilizers as well as organic products so as to give high yields with the best product quality devoid of contamination and less accumulation with heavy metals. Keywords: Agricultural practices, bio-fertilizers, chemical fertilizers, yield, organic products
... This fungal partner of symbiotic association belonging to glomeromycota that corresponds to eight different genera such as Acaulospora, Archaeospora, Entrophospora, Gigaspora, Glomus, Paraglomus, Sclerocystis and Scutellospora (Morton and Redecker, 2001). These genera form symbiosis with variety of plant varying from bryophytes to angiosperms and even single isolate can colonize variety of plants showing ecological specificity (Allen and Boosalis, 1983).Numerous ecophysiological studies have confirmed importance of AM symbiosis in the soil-plant interface, such as improving plant nutrition by better nutrient and water uptake, production of phytohormones, abiotic and biotic stress tolerance. Moreover, symbiosis is also helpful to improve soil structure by production of glomalin that bind small soil particles to form large aggregates. ...
... It has been shown by [73] that in field-grown tomato plants, root colonization by the AMF R. intraradices enabled plants to grow well under water stress conditions through an improvement of nutrient contents and water use efficiency. These beneficial effects of AMF on tomato tolerance to water stress have also been reported in several other plant species such as Lactuca sativa L. [74], Triticum aestivum L. [75], Lavandula spica L. [76], Allium cepa L. [77], Trifolium repens L. [78], Pistacia vera L. [79], Acacia auriculiformis A.Cunn. ex Benth, Albizia lebbeck (L.) Benth., Gliricidia sepium (Jacq.) ...
Arbuscular mycorrhizal fungi (AMF) establish symbiotic associations with most terrestrial plants. These soil microorganisms enhance the plant's nutrient uptake by extending the root absorbing area. In return, the symbiont receives plant carbohydrates for the completion of its life cycle. AMF also helps plants to cope with biotic and abiotic stresses such as salinity, drought, extreme temperature, heavy metal, diseases, and pathogens. For abiotic stresses, the mechanisms of adaptation of AMF to these stresses are generally linked to increased hydromineral nutrition, ion selectivity, gene regulation, production of osmolytes, and the synthesis of phytohormones and antioxidants. Regarding the biotic stresses, AMF are involved in pathogen resistance including competition for colonization sites and improvement of the plant's defense system. Furthermore, AMF have a positive impact on ecosystems. They improve the quality of soil aggregation, drive the structure of plant and bacteria communities, and enhance ecosystem stability. Thus, a plant colonized by AMF will use more of these adaptation mechanisms compared to a plant without mycorrhizae. In this review, we present the contribution of AMF on plant growth and performance in stressed environments.
... One factor which may be quite important in the establishment of alternative crops is the formation of proper mycorrhizal associations to maximize plant growth and yield (Fitzsimmons 2006). Some studies suggest that establishment of root systems colonized by mycorrhizal fungi can increase host plants' resistance to drought stress (Allen et al. 1983;Augé 2004;Rapparini and Peñuelas 2014). Mycorrhizae may increase drought tolerance of plants, a potentially critical driver as drought events have been predicted to increase in the Midwest (Mishra et al. 2010). ...
Although agriculture focuses on row crops in the Midwestern US, chestnut (Castanea) would be a possible multipurpose agroforestry crop in erodible locations within this region. As ectomycorrhizal (ECM) colonization is often crucial for tree establishment and production, we addressed the importance of ECM colonization on chestnut performance by assessing: (1) natural ECM colonization in an established chestnut orchard, and (2) the effect of ECM inoculation on seedling establishment and drought response in a greenhouse. We selected 50 Chinese American hybrid chestnuts trees in a commercial orchard and assessed their level of mycorrhizal colonization in relation to distance from an adjacent forest, the source of inoculum. In the green house, we grew 80 seedlings from this orchard with and without mycorrhizal inoculation. Half were harvested to assess inoculation success and biomass; the remainder were subjected to experimental water stress which was evaluated with chlorophyll fluorescence using Fv/Fm values. In the orchard planted with uninoculated plants, ECM colonization decreased with distance from adjacent oak forest (P = 0.015), the putative ECM source, with an average of 29% root tips colonized. ECM inoculation increased seedling aboveground biomass by 16.4% in the greenhouse and generated 1.14 times more, but smaller stomata on leaves. Water stress in ECM inoculated seedlings also recovered faster from an experimental drought having significantly higher Fv/Fm value (P = 0.004) than uninoculated seedlings. Our study clearly indicates that ectomycorrhizal colonization can help chestnut trees in their early growth and stress tolerance and should be included into field plantings to minimize dependence on agricultural amendments.
... Arbuscular mycorrhizal (AM) fungi are mostly known for aiding plants with the uptake of soil nutrients, such as phosphorus [1,2], and for helping plants better cope with abiotic [2][3][4][5] and biotic [2,[6][7][8][9][10][11] stress. Another aspect of this ubiquitous symbiosis that is intriguing involves the impact of AM fungi on plant immunity, especially against aboveground and belowground insect herbivores [12][13][14]. ...
This research examined aphid and plant responses to distinct levels (none, low, and high) of arbuscular mycorrhizal (AM) fungal root colonization by studying the association between potato aphids (Macrosiphum euphorbiae), potatoes (Solanum tuberosum), and AM fungi (Rhizophagus intraradices). It extends knowledge on gene expression changes, assessed by RT–qPCR, of ten defense-related genes at two time-points post-herbivory (24 h and 10 days), focusing on aphid-infested local leaves, non-infested systemic leaves, and roots. The results showed that aphid fitness was not altered by AM symbiosis. At 24 h, ETHYLENE RECEPTOR 1 gene expression was repressed in roots of aphid-infested non-mycorrhizal plants and aphid-infested plants with a high level of AM fungal root colonization, but not on aphid-infested plants with a low level of AM fungal root colonization. At 10 days, ALLENE OXIDE CYCLASE and POTATO TYPE I PROTEASE INHIBITOR were upregulated exclusively in local leaves of aphid-infested plants with a low level of AM fungal root colonization. In addition, local and systemic changes in plant gene expression appeared to be regulated exclusively by AM status and aphid herbivory. In summary, the gene expression data provide insights on mycorrhizal potato responses to aphid herbivory and serve as a starting point for future studies using this system.
... In addition, mycorrhiza is capable of increasing host resistance to root pathogens ( Pozo et al. 2010), increasing host tolerance to environmental stress due to salinity and drought ( Latef et al. 2016;Quiroga et al. 2017), and heavy metal contamination ( Upadhyaya et al. 2010). Moreover, mycorrhizal abundance and activities in the soil rhizosphere are largely determined by climate, host type, and soil water content or drought level ( Schubler et al. 2001;Moreira et al. 2007;Hernadi 2012;Sadhana 2014;Quiroga et al. 2017;Mathimaran et al. 2017;Choosa-nga et al. 2019), type and level of soil fertility, as well as altitude (Allen and Boosalis, 1983;Tahat and Sijam 2012;Kavitha and Nelson 2013;Mo et al . 2016). ...
Rai IN, Suada IK, Proborini M, Wiraatmaja IW, Semenov M, Krasnov G. 2019. Indigenous endomycorrhizal fungi at salak (Salacca zalacca) plantations in Bali, Indonesia and their colonization of the roots. Biodiversitas 20: 2410-2416. Cultivation of snake fruit, commonly known as salak usually done organically on dry land with limited fertilizer in Bali. This research aimed to observe and to identify the indigenous endomycorrhizal fungi on salak roots. The exploration was carried out by collecting soil and root samples in salak producing areas in Bali, i.e. Bebandem and Selat of Karangasem Regency, Payangan of Gianyar, and Pupuan of Tabanan Regency. At each location, 9 random samples were taken, resulting in a total of 36 samples. Spore extraction was carried out using a wet filtration technique followed by centrifugation according to the method by Brunndrett et al. (2009). Morphological identification was carried out at the genus and species level using the Manual for Identification of Mycorrhiza Fungi for identifying Vesicular-Arbuscular-Mycorrhiza (VAM) fungi (Schenk and Perez, 1990), while molecular identification was carried out according to Tedersoo et al. (2014). The percentage of root infections was carried out using the coloring method with trypan blue. The results showed there were only two genera of endomycorrhizae (Glomus and Entrophospora) identified at the locations of study sites. The results also showed that samples from Bebandem and Selat regions had 3 Glomus species, Payangan had 3 Glomus species and 1 Entrophospora species, while in Pupuan had only 2 Glomus species. Identification results based on morphological characters showed that all species in the genus Glomus consisted of 3 species, namely Glomus sp-1, Glomus sp-2, and Glomus sp-3, while one species in the genus Entrophospora was Entrophospora sp. Genetic identification results based on the nucleotide arrangement showed that Glomus sp-1 concluded as Glomus cubence, Glomus sp-2 concluded as Glomus custos, and Glomus sp-3 concluded as Glomus indicum, while Entrophospora species concluded as Entrophospora_sp_SH197095.06FU. The average of root colonization/ infection was very high, reaching 93.33% in Bebandem and Selat, 95.00% in Pupuan, and 100% in Payangan. The very high root infection rates indicated that the indigenous endomycorrhiza found in these areas was very adaptive in salak plantation, so there is an opportunity to be developed as biofertilizers.
... Plant species that experience a negative PSF perform worse in soil conditioned by conspecifics than in a control soil . Arbuscular mycorrhizal fungi (AMF) are thought to contribute to positive PSF, because they can increase plant nutrient supply (Aerts 2002;Read & Perez-Moreno 2003), stress resistance to drought (Allen & Boosalis 1983), and reduce susceptibility to root pathogens (Harrier & Watson 2004;Wehner et al. 2011 (Bennett et al. 2017) or seedling biomass (Moora & Zobel 1996). These differential outcomes indicate that our understanding of whether AMF facilitate or suppress seedling establishment and growth in natural systems, and how this may depend on the net PSF effect that plant species develop, needs to be further elucidated. ...
... In the case of alterations in the abundance of the Glomeraceae and Gigasporaceae, this is particularly interesting as these fungal taxa have been found to have disparate growth strategies, ERM production, speeds of nutrient transfer to their hosts and roles in pathogen protection (Dodd et al. 2000;Boddington and Dodd 2002;Powell et al. 2009;Chagnon et al. 2013). However, despite many early studies examining how the effects of individual AM fungal isolates on plant growth are altered by temperature (Hayman 1974;Schenck and Schroder 1974;Schenck and Smith 1982), water availability (Busse and Ellis 1985;Nelsen and Safir 1982;Allen and Boosalis 1983;Tobar, Azcón and Barea 1994) and atmospheric change (Jongen, Fay and Jones 1996), very few studies have directly empirically examined the consequences of these variables on the functioning of AM fungal communities. Indeed, their potentially changing role under drought and warming has not been investigated at all. ...
Arbuscular mycorrhizal (AM) fungi are amongst the most common and functionally important symbionts of terrestrial plants and are highly likely to be affected by global change. The potential consequences of this on plant growth and carbon and nutrient cycling has led to a growing demand for their inclusion in global change models. However, our understanding of their responses to environmental change remains limited. This review provides an overview of recent experiments attempting to predict the effects of atmospheric and climatic change on AM fungal community diversity, composition and functioning. This includes rising atmospheric carbon dioxide and tropospheric ozone levels, altered water availability, warming and nitrogen deposition. Changes detected are often highly variable and context dependent, but trends are emerging such as the similar responses of community composition to enhanced nitrogen deposition and atmospheric CO2, despite the likely contrasting effect of these environmental changes on carbon availability. The review also highlights shortfalls in our current knowledge and suggests priorities for future research, particularly advocating more integrated approaches linking the study of community characteristics and functions and examination of fine level genetic changes, wider geographical contexts and a greater range of AM fungal functions.
... The mechanism proposed for drought tolerance in AM plants has been credited to the increase in osmotic potential adjustments (Augé et al. 1986) by AM colonized plants due to increased water uptake, which further improves the stomatal conductivity and transpiration rate (Allen and Boosalis 1983) and is also supported by better mineral nutritional status particularly phosphorus (Hodge et al. 2010). Thus, overall the leaves are in a better hydrated state after AM colonization (Boomsma and Vyn 2008). ...
Drought is a serious and common threat to plant survival worldwide and is getting intensified due to global warming and decreasing water levels thereby possessing challenges on food security. The responses of plants to changing environment are complex. All adaption and acclimatization strategies are at physiological cost at the organism level which can affect ecosystem functioning at large. Mycorrhizae and endophytes are representative symbiotic association of the plants and fungi and are capable of modulating the physiological response of plants to water stress and overcome yield barrier. Water and nutrients available to plant are determined by the rhizospheric water potential which can be manifested to some extent by the AMF. The fungal community forming symbiosis with plants may exert their effect through phytohormones production, solubilization of nutrients, and induction of pathogen resistance or increasing abiotic stress tolerance through increased antioxidant levels in plants. While research supports the fungal endophytes and mycorrhizae as an ecofriendly alternative to combat drought stress, a better perceptive of physiological effects of these microbes to stress can develop a stronger and resilient agroecosystem.
... The mechanism proposed for drought tolerance in AM plants has been credited to the increase in osmotic potential adjustments (Augé et al. 1986) by AM colonized plants due to increased water uptake, which further improves the stomatal conductivity and transpiration rate (Allen and Boosalis 1983) and is also supported by better mineral nutritional status particularly phosphorus (Hodge et al. 2010). Thus, overall the leaves are in a better hydrated state after AM colonization (Boomsma and Vyn 2008). ...
... It has been estimated that about 20% of C fixed from photosynthesis is transferred from the plant to the fungus (Harrison, 1999). In addition, mycorrhizal plants exhibit resistance to drought (Allen & Boosalis, 1983;Sieverding, 1986), salinity (Bothe, 2012;Porcel et al., 2012), and diseases (Cordier et al., 1998;Pozo et al., 2002;Liu et al., 2007;Fiorilli et al., 2011;Campos-Soriano et al., 2012;Nair et al., 2015a,b;Bruisson et al., 2016;Delavaux et al., 2017;Wang et al., 2018). ...
This study sheds light on a poorly understood area in insect‐plant‐microbe interactions, focusing on aphid probing and feeding behavior on plants with varying levels of arbuscular mycorrhizal (AM) fungus root colonization. It investigates a commonly occurring interaction of three species: pea aphid Acyrthosiphon pisum, barrel medic Medicago truncatula, and the AM fungus Rhizophagus irregularis, examining whether aphid‐feeding behavior changes when insects feed on plants at different levels of AM fungus colonization (42% and 84% root length colonized). Aphid probing and feeding behavior was monitored throughout 8 hours of recording using the electrical penetration graph (EPG) technique, also, foliar nutrient content and plant growth were measured. Summarizing, aphids took longer to reach their 1st sustained phloem ingestion on the 84% AM plants than on the 42% AM plants or on controls. Less aphids showed phloem ingestion on the 84% AM plants relative to the 42% AM plants. Shoots of the 84% AM plants had higher percent carbon (43.7%) relative to controls (40.5%), and the 84% AM plants had reduced percent nitrogen (5.3%) relative to the 42% AM plants (6%). In conclusion, EPG and foliar nutrient data support the hypothesis that modifications in plant anatomy (e.g. thicker leaves), and poor food quality (reduced nitrogen) in the 84% AM plants contribute to reduced aphid success in locating phloem and ultimately to differences in phloem sap ingestion. This work suggests that M. truncatula plants benefit from AM symbiosis not only because of increased nutrient uptake but also because of reduced susceptibility to aphids.
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... The beneficial effects of the use of bioinoculants include increase in seed yield, better quality, improved crop uniformity and reduced losses due to environmental stresses and diseases [14]; [15]. Literature reported that, irrespective of the levels of nitrogen fertilizer applied to wheat crop following rice, treatment with Azotobacter used as biofertilizer singly or in combination with VAM, leads to yield improvement of wheat. ...
The present investigation entitled “Effect of Mycorrhizal Fungi and GA3 spray on rice seedling growth under shade house” was carried out during Kharif 2016 at AICRIP, Agricultural Resеarch Station, Mugad, UAS Dharwad. The experiment consisted of two factors having four level of treatment with bio agent and growth regulator spray and eight rice genotypes as factor-II with overall 32 treatment combinations replicated two times. Among treatments, soil application of Mycorrhizal Fungi 16 kg per acre + GA3 60 ppm at panicle initiation and 50 per cent flowering stage (M4), significantly increase the plant height of 109.41 cm, productive tillers of 10.75, chlorophyll content of flag leaf of 38.85, panicle length of 23.63 cm, days to 50 per cent flowering of 111.8 days, plant stand of 91.44 per cent, dehydrogenase activity of soil 50.60 µg TPF/g soil/day and root colonization of 55.26 per cent. Among eight rice genotypes significant maximum pant height of 118.74 cm by Hemavathi (V3), productive tillers of 11.09 by Mugad SIRI 1253 (V6), chlorophyll content of flag leaf of 37.44 by Abhilash (V2), panicle length of 24.68 cm by Intan (V1), days to 50 per cent flowering of 91.8 days by MGD 101 (V4), plant stand of 92.50 percent by PSB 68 (V8), dehydrogenase activity of soil 49.9 µg TPF/g soil/day by MGD 101 (V4) and root colonization of 55.95 per cent by MGD 101 (V4).
... However, other studies also showed an increased AMF colonization on Sorghum bicolor with drier soils (Sieverding 1981) or no differences of root AMF colonization for winter wheat between wet and dry treatments (Allen and Boosalis 1983). Besides root mycorrhizal colonization, low soil moisture also strongly inhibits soil extraradical hyphal length (Neumann et al. 2009). ...
Drought stress has strong inhibition in plant growth and crop production. Arbuscular mycorrhizal fungi (AMF) can colonize the roots of 80% of land’s plants to establish arbuscular mycorrhizal symbiosis. A relative short-term soil drought did not appear to discourage root AMF colonization, whereas a long-term soil drought intensity considerably decreased root colonization and hyphal growth in the soil. Such change in mycorrhizal development still strongly stimulated the improvement of plant growth and increased plant survival under drought stress. AMF had shown to enhance drought tolerance in various plants. Firstly, mycorrhizal plants could adapt the drought stress in morphology, especially leaf epicuticular wax and root morphology. And mycorrhizal plants possessed direct pathway of water uptake by extraradical hyphae. In addition, AMF enhanced drought tolerance of the host plant through physiological mechanisms in nutrient uptake and biochemical mechanisms regarding hormones, osmotic adjustment, and antioxidant systems. AMF also released glomalin into soil, defined as glomalin-related soil protein, to improve soil structure, thereby regulating water relations of plant/soil. Molecule mechanisms about expression of relevant stressed genes were clarified a bit more detail. Future perspectives in this field are provided.
... Indeed, wheat is easily mycorrhized by AMF under controlled greenhouse conditions and under field conditions (Cade-Menun et al., 1991;Neveen & Bahaa, 2011). These fungi have many advantages on the ecological level as well as the economic level, they establish symbiotic associations with plant roots, thus allowing the improvement of the agricultural products yield, and they translocate water and mineral nutrients such as phosphorus and nitrogen to the plants (Hu et al., 2010;Neveen & Bahaa, 2011).They positively affect plants tolerance to both abiotic (soil salinity and drought) as well as biotic (pathogens) stresses (Allen & Boosalis, 1983;Strullu et al., 1991). ...
In Algeria, in the semi-arid and arid areas cereal production is limited because of many constraints like lack of mineral elements (phosphorus and nitrogen), low organic matter and an insufficient water reserve due to the low rainfall. Most researches on durum wheat (Triticum durum Desf.) are undertaken to increase its productivity. In recent years several methods have been used including using microorganisms. Arbuscular Mycorrhizal fungi (AMF) appear to have important roles in plants in various soil conditions. In Algeria and particularly in the eastern regions, the diversity of AMF spores in the soil is so far little studied. In this context this study focuses on the study of the diversity and the abundance of AMF spores in Triticum durum Desf. fields in arid, semi-arid and coastal regions. Soil samples were collected and characterized and the spores isolated by the wet sieving methods were observed, counted and identified. The results of the physic-chemical characterization of all soil samples reveal a clay loam, loam clay and loam sandy soils with an alkaline pH (7.54-8.27), a total nitrogen content from 0.023 to 0.082% and phosphorus content ranging from 1.63% to 7.74%. We noted the presence of several morphotypes that were classified as follow: Glomeraceae, Acaulosporaceae and Scutellosporaceae with a predominance of Glomeraceae in different sites depending on climate and soil type. The presence of these families demonstrates a biodiversity of the eastern wheat fields of Algeria.
... Other explanations for the growth-promoting effects have been suggested, but these properties of VAM plants can almost always be attributed to improved nutrition, especially P nutrition (44). For example, it is well-documented that mycorrhizae increase hydraulic conductivity of roots (4,25,28) and, therefore, have been touted as a mechanism for increasing drought tolerance of plants (4)(5)(6)28). Safir et al. (46) demonstrated that fertilization of nonmycor rhizal soybeans duplicated the effect of mycorrhizae upon hydraulic conductivity. More recently, Graham and Syvertsen (25) found that mycorrhizal seedlings of 'Carrizo' citrange and sour orange, which were of equal size, but greater P content, had root systems that were almost twice as conductive as those of nonmycorrhizal plants. ...
The capability of vesicular-arbuscular mycorrhizal (VAM) fungi, symbiotically associated with roots of citrus and most other woody perennial crops, to dramatically enhance plant growth has attracted widespread interest among horticulturists. Unfortunately, too often scientists engaging in mycorrhizal research have become overly enthusiastic with growth responses that were created under artificial experimental conditions. Mycorrhizae are the “normal” condition of roots on citrus trees and most other horticultural plants in the field (44). The nonmycorrhizal condition is “abnormal” and often the consequence of “normal” horticultural practices, such as overuse of fertilizers and pesticides, soil sterilization, and plant production in sterile soilless media. These technical advances have led to rapid production of pathogen-free plants, but VAM fungi have been sacrificed in the process. The potential impact of mycorrhizal deficiency on the “quality” of citrus and other woody crops for transplant has not been fully evaluated. With the realization that VAM fungi are essential for the growth of citrus in field soils, the question of how to reintroduce and gain maximum benefit from mycorrhizae in greenhouse production of citrus and other woody plants needs to be assessed.
... Mycorrhizal fungi have been reported to improve plant water uptake under drought conditions (6,19,21,33,41). This improvement in plant water relations may be due to mycorrhizal fungi exploiting larger soil volumes, avoiding drought by maintaining a soil-root continuum (31), enhancing plant nutrition (6,19,33), or increasing stomatal conductance through regulation of abscisic (ABA) acid/cytokinin levels or osmoregulation (1)(2)(3)27). Marx and Bryan (22) postulated that increased plant survival at high root-zone temperatures was due to metabolites released by the fungal symbiont. ...
High root-zone temperatures can stress container-grown plants and ultimately reduce nursery productivity in the southern United States. Water relations of glasshouse-grown Berberis thunbergii DC ‘Atropurpurea’ Buxus microphylla Seibold and Zucc japonica and Pittosporum tobira , (Thunb.) Ait. ‘Wheeler’ were studied under high-temperature root-stress conditions using container-grown plants that were either colonized with vesicular arbuscular mycorrhizal fungi (VAM) or noncolonized. Predawn xylem water potential in stems (ψ stem ) increased initially (more positive) in response to high root-zone temperatures (40° to 45°C), and then decreased over a 5-day period. Stomatal conductance (g s ) and evapotranspiration (ET) were reduced incrementally over time in response to high root-zone temperatures. Root damage occurred, as indicated by reductions in root quality and g s at 35° and 40° for B. thunbergii and P. tobira , and at 40° and 45° for the more high-temperature-resistant B. microphylla. Colonization increased g s and ET of B. microphylla at ambient (25°) and high temperatures (45°) and increased ET of B. thunbergii at 25°. Colonized plants had lower (more negative) ψ shoot with initial exposure to increased root-zone temperatures; however, throughout the remainder of the study period there was little reduction in plant stress with the mycorrhizal isolates used. Root hydraulic conductivity (Lp) increased markedly in B. thunbergii compared to B. microphylla at 40° and 45°, indicating less high-temperature resistance in B. thunbergii roots. Mycorrhizal colonization did not moderate hydraulic conductivity at high root-zone temperatures of 40° and 45°. Of the two species, mycorrhizal B. thunbergii had lower L p at 25° and B. microphylla had lower L p at 35°.
... The plant provides photosynthates to the fungi and in turn the hyphae of arbuscular mycorrhizal (AM) fungus extend into the soil and provide water and nutrients, especially the immobile nutrients, to plants (Koide, 1991;Marschner & Dell, 1994). Therefore, increased tolerance to drought (Allen & Boosalis, 1983;Auge, 2004;Nelsen & Safir, 1982;Ruiz-Lozano et al., 1995) and significant improvement in growth and productivity of several plant species have been reported in mycorrhizal plants under water and nutrient deficiencies (Baslam et al., 2011;Citernesi et al., 1998;Estaun et al., 2003;Gerdemann, 1968;Mosse et al., 1975). In addition, protection against pathogens in mycorrhizal plants has also been shown in different cultivars (Castillo et al., 2006;Espinosa et al., 2014;Liu et al., 2007;Pozo & Azcon-Aguilar, 2007;Rabie, 1998;Watanarojanaporn et al., 2011). ...
This study was conducted to investigate the effect of mycorrhizal symbiosis on the levels of polyphenols in olive saplings. Rooted stem cuttings of olive cultivar, ‘Arbequina’, were inoculated with AM fungus Rhizophagus intraradices. The inoculated plants showed more robust growth after six months, and after nine months the increase in the mycorrhizal plant’s height was 146%, and the increase in number of leaves was 117% when compared to uninoculated controls. Polyphenols in the methanol extracts of leaves were separated by HPLC and the peaks identified by using commercially available standard compounds and comparing retention time and the mass obtained with the mass spectrometer. Oleuropein, which is a major component of the olive leaf polyphenols, increased in mycorrhizal plants compared to uninoculated plants by 42%, and its derivatives, oleuroside and ligstroside, increased by 68% and 48%, respectively. The highest increase was found in the levels of luteolin-7’-O-glucoside (107% increase), while its sister compound luteolin-4’-O-glucoside increased by 43%. Only verbascoside levels were lower in mycorrhizal plants versus non-mycorrhizal plants declining to below detectable limits. Thus, inoculation of olive saplings with mycorrhizal fungi produces very positive effects on the levels of olive leaf polyphenols. Higher levels polyphenols mean better quality of leaf material for use as herbal medicine.
... In the earliest work on the subject, Safir et al. (1971Safir et al. ( , 1972 concluded that AM symbiosis probably influences the water relations in soybean plants. In some instances, however, stomatal parameters are altered by AM symbiosis without altering leaf hydration (Allen and Boosalis, 1983;Osundina, 1995;Stahl and Smith, 1984). Perhaps the single most important indicator of a drought resistance strategy is the dehydration tolerance of a species, that is, tissue capacity for withstanding low water potential conditions. ...
Biotic and abiotic stresses take a heavy toll on crop productivity in soybean (Glycine max (L.) Merr.). To deal with this problem, considerable efforts have been made to understand the molecular mechanism underlying stress perception and tolerance in response to both biotic and abiotic stresses. Recent advances have highlighted several candidate genes that are involved in tolerance to more than one type of stress and, therefore, affect the outcome of the stress response. In this chapter, we summarize the current knowledge about the key transcription factors and signaling components known to regulate stress cross talk in soybean. In total, twenty genes have been demonstrated to confer tolerance to multiple stresses using transgenic approaches. However, to date, only three genes including GmERF3, GmERF057, and GmCAM4 are known to confer tolerance to both biotic and abiotic stresses. Further, in addition to the key genes, the potential of microRNAs and mycorrhiza in engineering broad spectrum stress-tolerant soybean varieties has been discussed.
... The main problem that faces plant growing in saline soils may be due to the high concentration of salts in the soil solution, which produces a high osmotic concentration (and correspondingly low soil water potential). AMF may improve the growth of plants under a variety of stress conditions (Allen and Boosalis, 1983), including salinity (Pfeiffer and Bloss, 1988; Poss et al., 1985). In places with relatively low Na contents and diverse plant cover, AMF spores and colonization levels were found to be high (Juniper and Abbott, 1993), the origin of that AMF is from edaphic conditions (Brundrett, 1991). ...
... Farahani et al. (2008) conducted a pot experiment and reported a higher RLWC in coriander under integrated application of AM fungi and P under drought stress condition. Further, water stressed plants have been found to accumulate organic osmolytes such as sugars and amino acids (proline) that are known to contribute to 'host plant tolerance' under water deficit conditions (Aziz et al., 2000). ...
Present investigation studied plant water relations and soil physical properties through AM fungi (Glomus mosseae) to mitigate drought stress in Himalayan acid Alfisol having low water retentivity. Experimentation was carried out at Palampur, India during 2009–2011 in okra–pea cropping system in randomized block design (RBD) replicated thrice with 14 treatments comprising arbuscular mycorrhizal (AM) fungi, varying phosphorus nutrition and irrigation regimes at 40 and 80% available water holding capacity. Integrated use of AM fungi at varying phosphorus (P) levels and irrigation regimes led to significantly higher relative leaf water content (3% each) in okra and pea besides significantly higher xylem water potential (27%) in pea over non-AM fungi counterparts. AM fungi enhanced water-use-efficiency in okra (5–17%) and pea (12–35%) over non–AM fungi counterparts. AM fungi also improved water holding capacity (5–6%) and mean weight diameter of soil particles (4–9%) over non–AM fungi counterparts; but, had nominal or no effect on bulk density. Mycorrhizal plants maintained higher tissue water content imparting greater drought resistance to plants over non–mycorrhizal plants at moisture stress. It is inferred that integrated application of AM fungi and P at varying irrigation regimes improved the plant water relations vis-à-vis drought resistance, crop productivity, WUE, soil aggregation and water holding capacity in okra–pea sequence in Himalayan acid Alfisol.
Arbuscular mycorrhizal fungi (AMF) or arbuscular mycorrhizae (AM) that invade the plant roots or reside in the rhizosphere are considered to be advantageous for plant’s development. AM helps the host plants by making favourable alterations in the rhizospheric soil properties and providing vital mineral nutrients, particularly phosphorus. As symbionts with terrestrial plant roots, arbuscular mycorrhizae (AM) are included under the phylum Glomeromycota. The rhizosphere is the place where AM–plant association begins, and it involves a sequence of chemical induction that is released by both the fungus and the plant. Plants commence communication with AM by secretion of chemical induction into the root zone area of plant, in response to deficiency of nutrients like phosphorus and nitrogen, because AM’s major role in the AM–plant association is to give important nutrients. Most AM spores do not necessarily require the chemical cues to germinate. AM spores were thought to be gone through many stages of germination prior to the discovery of chemical signals from a possible host. The fungus actually looks for plant exudates and then branches out in the direction of the exudates it finds.
Plants have many mechanisms of tolerance to avoid the harmful consequences of various environmental stresses. One of the most crucial tools is the antioxidant system that involves in tolerance mechanism. Osmolyte formation is aided by AM and also supports the ions’ preferential absorption. Moreover, phosphorus nutrition of host plants is not only boosted by AM rather its development and tolerance potentiality towards drought stress and diseases are also improved. The possibility of regulation of plant growth by using AM has been the subject to numerous research studies.
AM can play vital roles in promoting agricultural sustainability, including acting as root symbiont, biofertilizers, enhancing plant water and nutrient absorption, sequestering carbon, making micronutrients more readily available to plants, and improving the surface absorption capacity of host roots. In view of the above, this chapter aims to depict the current state of AM research and its physiology of symbiosis, with a particular focus on AM-induced alterations in plant’s antioxidant and osmolyte metabolisms that support significant adaptations in plants under adverse conditions.
Potato (Solanum tuberosum L.), is the third most important crop in the world after rice and wheat in terms of consumption. This crop needs optimal irrigation to achieve proper growth and ultimately acceptable yield. Considering the climatic conditions of the Iran, it is necessary to study the effects of deficit irrigation on potato and to investigate the methods of increasing the drought stress resistance of this crop.
in order to investigate the tuber yield, physiological indices and water use efficiency of potato in the two cropping years 2019-2020, a factorial experiment was conducted in a randomized complete block design with three replications in the Agricultural Research and Training Center of Natural Resources of Hamadan Province. Each year, the experimental treatments included irrigation interval as the first factor at four levels (irrigation after 70, 90, 110 and 130 mm cumulative evaporation from Class A evaporation pan) and the second factor was bio-fertilizer at six levels. Bio-phosphate (B), Glomus. mossea (GM), G. fasciculotum (GF), G. mossea+ Bio phosphate (BGM), G. fasciculotum + Bio-phosphate (BGF) and Control (C) were conducted in factorial arrangement.
The results showed that increasing irrigation stress reduced tuber yield but the application of Bio-fertilizers improved the adverse effects of drought stress. The results also showed that the drought stress of 130 mm evaporation compared to the treatment of 70 mm evaporation (Control), led to a decrease in tuber yield and leaf area index, by 46.79 and 46.81%, respectively. The results related to potato yield showed that the use of three bio-fertilizers G. mossea, G. fasciculotum and Bio-phosphate had the greatest effect on tuber yield and leaf area index. The improvement tuber yield under conditions of severe drought stress by using bio-fertilizer treatments compared to the control was 38.65% for G. mossea, 37.41% for G. fasciculatum, 32.63% for bio-phosphate, 20.11% for bio-phosphate + G. mossea and 12.91% for bio-phosphate + G. fasciculatum. Based on the results the application of Glomus fasciculatum and G. mossea bio-fertilizers in the treatment of severe drought stress modified the stress effects by 36.36 and 30%, respectively, compared to the non-use of bio-fertilizer. Application of biofertilizers in all irrigation treatments moderated the adverse effect of drought stress on water use efficiency index. The use of Glomus musea, G. fasciculatum and biophosphate biofertilizers led to an increase in water use efficiency index in severe drought stress treatment compared to the control treatment by 38.38, 36.6 and 30.87%, respectively. Conclusion: Therefore, the use of mycorrhizae G. fasciculatum and G. mossea also bio-Phosphate is recommended separately for areas that suffer from drought stress during the potato growing season.
Mycorrhizae are mutualisms between plants and fungi that evolved over 400 million years ago. This symbiotic relationship commenced with land invasion, and as new groups evolved, new organisms developed with varying adaptations to changing conditions. Based on the author's 50 years of knowledge and research, this book characterizes mycorrhizae through the most rapid global environmental changes in human history. It applies that knowledge in many different scenarios, from restoring strip mines in Wyoming and shifting agriculture in the Yucatán, to integrating mutualisms into science policy in California and Washington, D.C. Toggling between ecological theory and natural history of a widespread and long-lived symbiotic relationship, this interdisciplinary volume scales from structure-function and biochemistry to ecosystem dynamics and global change. This remarkable study is of interest to a wide range of students, researchers, and land-use managers.
Biofertilizers and biological products are increasingly being used to enlarge the productivity of crops. Of these, microbes known as Plant Growth-Promoting Microorganisms (PGPM) are the most valuable as biofertilizers, having the capacity to directly impact the growth and development of plants. Plant Growth-Promoting Fungi (PGPF) and Plant Growth-Promoting Bacteria (PGPB) help crops to face biotic and abiotic stresses by enhancing the defense system and several other parameters related to plant growth. This chapter is focused on explaining the function and positive influence of the PGPF and PGPB on several crops, and also to provide a general view of the application of microorganisms in modern agriculture
Studies have shown arbuscular mycorrhizal fungi (AMF) enhance phosphorus (P) uptake and drought tolerance in maize (Zea mays L.) grown in semiarid soils. However, little is known regarding the contribution of AMF to maize treated with different levels of phosphorus and grown in different soil moisture levels. This study was conducted to determine the effects of AMF (Glomus fasciculatum) inoculation on growth and P uptake of maize treated with different levels of soil P and soil moisture. Different P levels (0, 50, and 100 kg P ha-1) were applied on maize grown in soils with and without mycorrhizal fungi, and at different moisture levels producing-0.05,-0.4,-0.8, and-1.5 MPa of drought stress. Increasing P rates significantly (p < 0.05) reduced mycorrhizal colonization. Mycorrhizal colonization was higher under moderate than under lower soil moisture levels. Drought stress × soil P content × AMF inoculation interaction had significant (p < 0.05) effect on maize shoot and root dry weight and tissue P concentration. Overall, results of this study suggest that mycorrhizal inoculation enhances P uptake and maximizes maize biomass under low, moderate, and high soil moisture conditions without P applications. Except for the lowest soil moisture level (-1.5 MPa), mycorrhizal plants produced higher biomass, with greater tissue P content than nonmycorrhizal plants at all soil P and soil moisture levels. These results indicate that establishing efficacious AMF with maize could be an efficient alternative for growers than relying on P fertilizer application and its associated costs and environmental concerns.
Phytoremediation is not a new concept. However, it is important to understand plant’s ability to remediate contaminated soil and water alone or in association with microorganisms by absorbing toxic substances, metabolizing them into useful compounds within and eventually transpiring excess of them. Native plants due to their unique characteristics are able to clean up soil and water very often in association with mycorrhizal fungi. This chapter focuses phytoremediation as eco-friendly cleaning tool, its basic strategies, role of native plants in restoring wetland habitats and limitations.
Soybean [Glycine max (L.) Merrill] is counted as the most important legume oilseed crop worldwide known for its high protein (35–40%) and oil (18–20%) content. Global climatic changes with persistent droughts are a major challenge and limiting factor for sustaining the yields of soybean. Several adaptations and mitigation strategies are required to cope with drought stress. Conventional breeding approaches employed for evolving drought-tolerant lines although is a viable solution requires more time and is long-term approach. As an alternate strategy, the use of microbial endophytes (bacterial and fungal) could play a significant role in the alleviation of drought stress and confer tolerance to plants. These beneficial microorganisms colonize the rhizosphere/phyllosphere of plants and impart drought tolerance by producing exopolysaccharides (EPS), phytohormones, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and volatile compounds and inducing accumulation of osmolytes and antioxidants, upregulation or downregulation of stress-responsive genes, and alteration in root morphology thereby making plants tolerant to cope during drought stress. The term induced systemic tolerance (IST) was also discussed on how physical and chemical changes induced by endophyte in plants which result in enhanced tolerance to drought stresses. In the present chapter, we also elaborated the role of bacterial and fungal endophytes and underlying mechanisms involved in helping soybean plants to cope with drought stress.
Phosphorus (P) availability to plants is a major constraint in acid soils. A study was conducted to determine the effect of arbuscular mycorrhizal fungi (AMF) under varying inorganic P and irrigation regimes on P availability and P-use efficiency in garden pea (Pisum sativum L.) in a Himalayan acid Alfisol. The experiment comprised of 14 treatments replicated thrice in a randomized block design. The results revealed that integrated use of AM fungi and inorganic P at either of the two irrigation regimes (IW/CPE0.6 or IW/CPE1.0) enhanced the green pea pod weight, green pod productivity and agronomic efficiency of applied P to the extent of 8.4%, 7.2% and 30.7%, respectively, over non-AMF counterparts as well as “generalized recommended NPK dose and irrigations (GRD).” AMF inoculation also led to enhanced nitrogen (N), P and potassium (K) acquisition (uptake) by 16.3%, 18.2% and 6% over non-AMF counterpart treatments. Further, AMF inoculation at varying P and irrigation regimes sharply enhanced the rooting depth (21.4%), root volume (23.5%), root dry weight (14.9%), root weight density (13.7%) as well as N concentration in root nodules (3.4%) over non-AMF counterparts and GRD practice. AMF also enhanced the mycorrhizal root colonization by 3.2 folds at flowering stage in AMF inoculated pea plants. AMF-imbedded treatments did not alter the available soil nutrient status (macronutrients and micronutrients) significantly in comparison to non-AMF counterparts in pea, available P status, however, increased to the extent of 6.5% over initial status. Further, AMF imbedded plots showed a slight build-up in soil organic carbon with nominal decrease in soil bulk density. AMF inoculation in pea also led to fertilizer P economy by about 25% soil-test-based P dose. Overall, AMF holds great potential in enhancing nutrient acquisition especially P besides influencing root morphology in order to harness better crop yields vis-à-vis fertilizer P economy by about 25% soil-test-based P dose in Himalayan acid Alfisol.
Core Ideas
Glomus spp. dominate the arbuscular mycorrhizal fungal (AMF) community in eastern red cedar (ERC) roots.
Young seedlings harbor the most diverse AMF, similar to grassland soils from the same site.
AMF diversity within ERC roots tended to decrease with plant age suggesting narrower plant and edaphic selection pressures with increasing ERC stand density.
A change in biotic and abiotic factors resulting from displacement of grassland with ERC is likely responsible for successional changes in the AMF community.
Eastern red cedar (ERC; Juniperus virginiana ) is an invasive species of juniper native to eastern North America that causes significant economic loss to grasslands. Recent findings of high molecular diversity of arbuscular mycorrhizal fungi (AMF) in soils under ERC stands led us to consider that the invasiveness of ERC into grasslands may arise in part from its ability to form associations with extant grassland AMF communities. The diversity of AMF in roots of ERC was determined for five age groups ranging from 1 to 65 yr old and varying in stand density from individual seedlings in grassland (<5 yr) to closed ERC canopies devoid of grass species (65 yr). Roots were analyzed by nested polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) fingerprinting, cloning, and insert screening by DGGE, and sequencing of ribosomal DNA small‐subunit regions. Phylogenetically analyzed AMF sequences were used to define phylotypes. The majority of the sequences obtained were classified into Glomus Group A, with only a few belonging to Gigasporaceae and Acaulosporaceae , the latter two largely restricted to roots from ERC < 5 yr old. The richness of phylotypes tended to decrease with time, ranging from 11 in the youngest age group (1–5 yr) to 4 in the oldest age group (46–65 yr). Abundance of phylotypes varied greatly among the age groups. Overall, AMF diversity within ERC roots tended to decrease with plant age suggesting narrower plant and edaphic selection pressures with increasing ERC stand density.
Drought dramatically reduces crop yield, therefore remains as a major threat to food security. Overcoming drought by crop plants is a complex phenomenon – where plants find ways mainly through physiological adaptation. However, in nature, the plants rely also on microbes for mitigating the drought effects. Below ground association of plant roots with rhizosphere microorganisms for tolerating drought has been though established earlier, the exact mechanism is being understood only recently. The role of below ground microbes, particularly by the arbuscular mycorrhizal fungi (AMF), in drought tolerance by crop plants is currently a key research topic. The significance and highlights of the recent research as well as the past understanding of mechanisms by which crop plants tolerate drought through association of soil beneficial microbes, particularly with that of the AMF, is discussed in this review.
The formation of a mycorrhizal symbiosis is considered a widespread strategy of plants to obtain advantages under selection pressure in natural ecosystems. Most cultivated plant species can be infected by mycorrhizal fungi. Depending on the host plant and the infecting fungus, different mycorrhizae are formed: ectomycorrhizae, ericaceous, orchidaceous, and vesicular- arbuscular mycorrhizae (VAM). The main importance for plant production within this group has to be attributed to ectomycorrhizae (forestry) and VAM (most agricultural and horticultural plants).
Plants are constantly subjected to biotic and abiotic stress factors, from their planting time up to the harvesting, transport, storage and consumption of plant products. These stresses exert deleterious harmful effects on crop health as well as cause huge losses to their production worldwide. To combat these stress factors, researchers all around the globe are involved in procuring management practices ranging from traditional genetics and breeding techniques to present day available novel biotechnological tools. Use of microorganisms is one such method by which both abiotic and biotic stress can be tackled in an economical, ecofriendly and successful manner. Plant growth-promoting rhizobacteria (PGPR) are the bacteria living in rhizosphere region and promoting plant growth and suppressing stress components as well. Different microorganisms acquire different mechanisms to fight with these plant stresses. In this chapter, an effort has been made to impart the knowledge about the abiotic and biotic stress factors, their management in an efficient and novel way.
Vol. 5, No. I The effects of Glomus fasciculatnm and soil water condition were studied in soybean and maize. Two harvests were carried out to measure the growth response and mycorrhlzal colonization. G. fascicalatum increased plant and grain dry weights at both harvests of the two plants but the response was not always statistically significant. There was no interaction observed between Inoculation and sail water condition. Reduction In soil water condition reduced the percentage of mycorrhizal colonization and consequently reduced plant and grain dry weights in inoculated treatment. Similarly in uninoculated controls, soil water condition decreased both plant and grain dry weights.
Recovery from water stress was studied on similarly sized VA mycorrhizal and non-mycorrhizal rough lemon seedlings (Citrus jambhiri Lush). VA mycorrhiza affected stomatal conductance, photosynthesis and proline accumulation, but not leaf water potential, suggesting that most of the effect of the mycorrhizal association is on stomatal regulation rather than on root resistance.
The wilty tomato mutant flacca, the normal cultivar Lycopersicon esculentum Mill. Rheinlands Ruhm, and abscisic acid-induced phenotypic revertants were compared with respect to ethylene evolution, activity of tryptophan aminotransferase, and [1-(14)C]indoleacetic acid decarboxylation.The level of ethylene evolution was higher in flacca plants than in the normal cultivar. Ethylene evolution was reduced to the wild type level in abscisic acid-induced phenotypic revertants and to a lesser extent in mutant plants grown under humid conditions. Leaf epinasty, which characterized flacca plants in the present experiments, did not appear in absciscic acid-treated mutant plants, but did appear under high humidity. Tryptophan aminotransferase activity, similar to ethylene evolution, was higher in flacca plants and was reduced to the normal level by abscisic acid treatment. Indoleacetic acid decarboxylation was similar in mutant and normal plants, but was increased by abscisic acid treatment. The relationships among ethylene, auxin, and the morphological symptoms which characterize the mutant are discussed.
A simplified method of clearing and staining large numbers of plant roots for vesicular-arbuscular (VA) mycorrhizal assay is presented. Equipment needed for handling multiple samples is described, and two formulations for the different chemical solutions are presented. Because one formulation contains phenol, its use should be limited to basic studies for which adequate laboratory exhaust hoods are available and great clarity of fungal structures is required. The second staining formulation, utilizing lactic acid instead of phenol, is less toxic, requires less elaborate laboratory facilities, and has proven to be completely satisfactory for VA assays.
Mycorrhizal fungi were associated with citrus roots or soils in 78 of 79 orchards and nurseries in California and in 64 of 66 citrus orchards and nurseries in Florida. Glomus fasciculatus, G. macrocarpus, G. etunicatus, G. constrictus, and Sclerocystis sinuosa were present in both states. In addition, G. microcarpus and G. monosporus were found in California. Gigaspora margarita and G. mosseae were associated with citrus in Florida but not in California. Glomus fasciculatus was consistently associated with young trees (0-30 yr), whereas G. constrictus was consistently associated with older trees (30-70 yr). Total numbers of mycorrhizal chlamydospores associated with citrus in California were negatively correlated with soil P and organic matter, but were positively correlated with soil Na and pH. Glomus macrocarpus was more frequently found in California citrus soils of high P content than was G. microcarpus, and G. monosporus appeared to inhabit soils of higher B, Ca + Mg, or salinity than several other mycorrhizal fungi. In California, chlamydospores of both G. fasciculatus and G. constrictus were most numerous from November to May and least numerous from June to September.
The yearly incidence of root colonization and extramatrical spores of vesicular-arbuscular (-VA) mycorrhizal fungi were determined for six agronomic crops grown in monoculture for 7 yr on a newly cleared woodland site in northwest Florida. Thirteen species of VA-mycorrhizal fungi were identified from the test site from 1972 to 1978. Sorghum yielded the greatest number of species (12) from a single crop during this period. The highest number of spores was associated with soybean and the lowest number of spores was found in the native woodland. Spores of Gigaspora margarita, G. gregaria, and G. gigantea were most numerous from soil around soybeans while Glomus fasciculatus and G. clarus were most numerous around roots of bahia grass. Acaulospora spp. were most abundant from soil around cotton and peanut. The yearly incidence of Gigaspora margarita spores increased while G. gregaria and G. gigantea decreased in numbers during the 7-yr study. Glomus macrocarpus var. geosporus and G. fasciculatus were observed in 1971 and/or 1972 but were not recovered again until 1978. Only two species, Gigaspora margarita and G. gregaria, were recovered each yr that samples were taken. The highest level of root colonization occurred in 1972 and was followed by a decline in 1973–1974, but mycorrhizae showed a general increase in 1975–1976. It is suggested that the observed changes in the incidence of VA-mycorrhizal fungi were primarily due to the agricultural system of monoculture.
Vesicular-arbuscular endomycorrhizae were observed in association with the following plants: Atriplex canescens (Pursh) Nutt., Eurotia lanata (Pursh), Amelanchier oreophilus A. Nels., Amelanchier utahensis Koehne, Cercocarpus montanus Raf., Fallugia paradoxa (D. Don) Endl., Holodiscus dumosus (Nutt.) Heller, Purshia tridentata (Pursh) DC., Fendlera rupicola Gray, Philadelphus microphyllus Gray, Quercus gambelii Nutt., Symphoricarpos spp., Artemisia tridentata Nutt., and Rhus trilobata Nutt. Root fungi were stained using acid fuchsin in chloral hydrate solution. Fungal spores were extracted from soil by centrifugal flotation or sieving-decanting methods.
Bouteloua gracilis was grown in defined, axenic culture with and without vesicular–arbuscular (VA) mycorrhizae. Leaves and roots of mycorrhizal and nonmycorrhizal plants were harvested and assayed for cytokinin content using a soybean callus tissue bioassay. Total cytokinin activity was 57 and 111% greater in leaves and roots, respectively, in mycorrhizal over control plants. Cytokinin activities, separated using paper chromatography with water saturated n-butanol as a solvent, doubled in roots and leaves at Rf values of 0.3 and 0.9 and increased 9-fold in roots at an Rf value of 0.1 with infection. This appears to be the first demonstration of altered cytokinin levels in plants resulting from mycorrhizal infection.
Mycorrhizal fungi were associated with citrus roots or soils in 78 of 79 orchards and nurseries in California and in 64 of 66 citrus orchards and nurseries in Florida. Glomus fasciculatus, G. macrocarpus, G. etunicatus, G. constrictus, and Sclerocystis sinuosa were present in both states. In addition, G. microcarpus and G. monosporus were found in California. Gigaspora margarita and G. mosseae were associated with citrus in Florida but not in California. Glomus fasciculatus was consistently associated with young trees (0-30 yr), whereas G. constrictus was consistently associated with older trees (30-70 yr). Total numbers of mycorrhizal chlamydospores associated with citrus in California were negatively correlated with soil P and organic matter, but were positively correlated with soil Na and pH. Glomus macrocarpus was more frequently found in California citrus soils of high P content than was G. microcarpus, and G. monosporus appeared to inhabit soils of higher B, Ca + Mg, or salinity than several other mycorrhizal fungi. In California, chlamydospores of both G. fasciculatus and G. constrictus were most numerous from November to May and least numerous from June to September.
(1) The % root infection of Agropyron smithii and A. intermedium by vesicular-arbuscular mycorrhizae was measured and soil spores were counted in six reclaimed stripmine sites in Wyoming. (2) On 2- and 3-yr old sites % infection and spore counts were c. 50% or less than native prairie levels. (3) Spore counts of a 3-yr old disked prairie site were not different from the undisturbed prairie level, but infection was significantly lower. (4) Spore counts of the reclaimed sites were not highly correlated with % root infection. (5) Five of seven annuals which colonized the reclaimed and disked sites were non-mycorrhizal.
The yearly incidence of root colonization and extramatrical spores of vesicular-arbuscular (VA) mycorrhizal fungi were determined for six agronomic crops grown in monoculture for 7 yr on a newly cleared woodland site in northwest Florida. Thirteen species of VA-mycorrhizal fungi were identified from the test site from 1972 to 1978. Sorghum yielded the greatest number of species (12) from a single crop during this period. The highest number of spores was associated with soybean and the lowest number of spores was found in the native woodland. Spores of Gigaspora margarita, G. gregaria, and G. gigantea were most numerous from soil around soybeans while Glomus fasciculatus and G. clarus were most numerous around roots of bahia grass. Acaulospora spp. were most abundant from soil around cotton and peanut. The yearly incidence of Gigaspora margarita spores increased while G. gregaria and G. gigantea decreased in numbers during the 7-yr study. Glomus macrocarpus var. geosporus and G. fasciculatus were observed in 1971 and/or 1972 but were not recovered again until 1978. Only two species, Gigaspora margarita and G. gregaria, were recovered each yr that samples were taken. The highest level of root colonization occurred in 1972 and was followed by a decline in 1973-1974, but mycorrhizae showed a general increase in 1975-1976. It is suggested that the observed changes in the incidence of VA-mycorrhizal fungi were primarily due to the agricultural system of monoculture.
Wheat cultivars inoculated with Glomus mosseae show different degrees of mycorrhizal infection and mycorrhizal dependency. Mycorrhizal dependency was affected by root and root/shoot (R/S) ratio dry wts, but neither mycorrhizal dependency nor mycorrhizal infection levels were directly affected by N, P, K, Ca or Mg concentrations in plant tissues.
Absence of mycorrhizal infection in some wheat varieties was associated with lack of sugar exudation from the roots rather than with the sugar content of the roots. VA infection led to a decrease in the reducing and total sugar content of root extracts, and this effect was correlated with the degree of mycorrhizal infection.
The rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomus fasciculatus, to determine the influence of vesicular‐arbuscular mycorrhizae on water status, stomatal behaviour and photosynthesis as well as gross plant morphology, biomass and phosphorus content. Mycorrhizal infection increased transpiration rates by over 100% with 50 to 70% lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not different between mycorrhizal and non‐mycorrhizal plants indicating that whole‐plant resistance to water transport was reduced by more than 50%. Photosynthetic rates under saturating light conditions increased 68% with infection as a consequence of a 33% reduction in stomatal resistance and a 67% reduction in mesophyll resistance to CO2 uptake. Mycorrhizal infection did not affect biomass or gross plant morphology after 30 weeks of growth, but increased chlorophyll and phosphate concentrations by 28% and 70% respectively. These physiological changes indicate that mycorrhizae may substantially alter survival ability of Bouteloua gracilis.
A two-compartment growth chamber in which the aboveground plant materials were exposed to ¹⁴CO2 and the belowground portion was exposed to ¹⁵N2 under normal atmospheric pressure was designed for carbon and nitrogen transfer studies. Vicia faba infected with vesicular-arbuscular fungus Glomus mossae and non-mycorrhizal plants fixed similar quantities of N2 at an age of 6½ wk. Approximately 0.10 mg N was fixed∙g⁻¹ dry plant materials∙day⁻¹ and 40 mg C∙g⁻¹ dry matter day⁻¹ were synthesized by mycorrhizal and non-mycorrhizal fababeans during 48 h exposure to ¹⁴CO2 at 6½ wk with no apparent difference in yield of dry matter. The non-mycorrhizal plants transferred 37% of the fixed ¹⁴C beneath ground. The mycorrhizal ones transferred 47% of the fixed ¹⁴C beneath ground. Most of the difference could be accounted for in the belowground respiration. The ¹⁴CO2 produced by root-microbial systems of the mycorrhizal fababeans was twice as great as that of the nonmycorrhizal; both contained active rhizobium.
The growth and yield response of greenhouse‐grown soybean plants to colonization by 19 isolates (including 6 Glomus and 3 Gigaspora species) of vesicular‐arbuscular mycorrhizal fungi is reported. Each isolate was evaluated in a high (169 kg/ha Bray‐I P 2 O 5 ) and a low (50 kg/ha Bray‐I P 2 O 5 ) fertility soil. Colonization by most Glomus isolates significantly increased plant top dry weight and seed yields, and of these isolates most produced larger increases in dry weight in the low fertility soil. Colonization by five of the Gigaspora isolates did not significantly affect top dry weight and seed yield in the high or Iow fertility soil. The value of comparative testing of species is discussed.
In a sand-dune system at Tentsmuir Point, Fifeshire, Scotland, Glomus fasciculatus was the only endophyte present on roots of pioneer colonizing grasses. This fungus formed sporocarps and spore aggregates in the soil and in association with organic fragments, particularly root tissues. Amounts of infection and external mycelium varied with vegetation zone and season, but both became greater with dune stabilization and infection increased during summer and autumn.
Growth of Ammophila arenaria and Agropyron junceiforme in unsterile foreshore sand was improved when mycorrhizal with G. fasciculatus and G. macrocarpus var. geosporus. Experiments in dune sands, with maize as a test plant, gave better growth with both these endophytes than with either alone, but indicated the complexity of interaction between host, endophyte and edaphic factors. The possible significance of mycorrhizas in nutrientpoor and unstable habitats is discussed.
Extra-matrical spores of Endogone were found to be common in cultivated soils in Scotland. Six types of spores are described which are believed to represent distinct species. In preliminary inoculation experiments 4 of the 6 formed endotrophic mycorrhiza: three of these formed arbuscules and vesicles, and one formed only arbuscules. In field soil extra-matrical spores are much more abundant than spores formed in sporocarps.
The relationship between stomatal activity and leaf water potential components was examined for several sorghum [ Sorghum bicolor (L.) Moench] genotypes as a function of growth stage under semi‐arid field conditions. During vegetative development, prior to flowering, genotypic differences were observed in the leaf water potential required to initiate stomatal control of transpirational water loss and the rate of change in conductance per unit change in leaf water potential. No significant genotypic differences existed in conductance when leaf water potential was high. After flowering and attainment of maximum leaf size, conductance remained high even when the leaf water potentials declined to −24 to −26 bars.
The relationships between leaf water potential components were examined to help explain the leaf conductance observations. Genotypic differences were observed in the leaf water potential‐leaf turgor potential relationships at each growth stage. Prior to flowering, as leaf water potential declined, leaf turgor declined accordingly with little evidence of osmoregulation, and all genotypes reached calculated 0 turgor at essentially the same leaf water potential (−18 to −20 bars). Genotypic differences were also observed in the leaf turgor‐stomatal conductance relationships.
After flowering, during the grain filling stage, significant genotypic differences were observed in the degree of osmotic adjustment. The genetic range in osmotic adjustment represents a potentially important adaptive mechanism to water stress which allows for maintenance of turgor and thus of metabolic functions dependent on turgor. Apparently, water conservation through stomatal control is practiced to some extent in sorghum prior to the onset of reproductive development; however, after flowering photosynthetic productivity is apparently maintained at the expense of water conservation.
The effects on water status and growth of controlled cycles of water stress applied at various stages of development were studied on a semi-dwarf spring wheat (Triticum aestivum L.). The plants were grown in controlled environment chambers of the Duke University Phytetron at 24/18°C with a 12-h photo-period at about 600 μE m−2 s−1. Groups of plants were subjected to severe water stress by withholding irrigation, beginning at the 7th leaf, early anthesis, or early dough stages of development. A second cycle started 9 to 13 days after termination of the first cycle and maintained until the flag leaf water potential reached –25 bars at each of the growth stages.
The lower leaves showed sign of wilting as indicated by curling in the first drying cycle at –7 bars and in the second cycle at –9 bars of leaf water potential during all stages of growth. Although these leaves recovered completely upon rewatering, onset of senescence was accelerated by three days in stressed plants. A preliminary drying cycle did not increase the ability of the plants to withstand subsequent stress because of severity of stress. Water stress of –25 bars at all three stages of growth reduced seed yield. The reduction was greater when a second stress cycle was also applied. Stress applied during early anthesis stage produced the smallest and the least number of seeds. The lack of osmotic adjustment probably was due to very rapid and severe development of water stress.
Root growth characteristics and water transport were compared between non-mycorrhizal Bouteloua gracilis and vesicular–arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus. Mycorrhizal plants did not have significantly different leaf area or root length from non-mycorrhizal plants, but did have significantly fewer and shorter root hairs. Mycorrhizal plants had 50% lower leaf resistance with no change in leaf or root water potentials; thus transpiration was increased 100% with a 50% reduction in whole-plant, soil-to-root and root-to-leaf resistance. Assuming that the difference in water uptake was due to transport via the mycorrhizal hyphae, estimated fungus-to-root transport was 2.8 × 10−5 mg s−1 per hyphal entry point which compares favourably with evapotranspiration rates measured in other coenocytic fungi. Thus, one of the major factors causing increased water transport and reduced resistance to water through-flow with mycorrhizal infection may be the increased surface area provided by the hyphae.
Root samples collected in grasslands of the Serengeti ecosystem, Tanzania, were found to be mycorrhizal and infection frequency was positively correlated with grazing intensity across sites. To examine the role of mycorrhizae in a grazing ecosystem, I analyzed the growth, morphology and gas exchange of mycorrhizal and nomycorrhizal plants of Panicum coloratum L. under different fertilization and clipping regimes. Both severe clipping and high nitrogen promoted more prostrate shoot growth but inhibited root growth. However, mycorrhizal infection promoted a prostrate shoot morphology and enhanced root growth. Photosynthesis was inhibited by clipping, however; at the most severe clipping and nitrogen regime, photosynthesis of the mycorrhizal plants was not affected whereas the largest inhibition of photosynthesis occurred in similarly treated nonmycorrhizal plants. Discussion of the putative roles of mycorrhizae in intensely grazed ecosystems is presented.
The effect of Gigaspora margarita an endomycorrhiza—forming fungus, on the growth and chemical composition of perennial ryegrass plants grown at three concentrations and two sources of N were studied. The yield of plant tops was significantly depressed by mycorrhizal infection. Mycorrhizal plants had higher concentrations of free NH4+ (and, consequently, higher cation excess concentrations), suggesting an impairment of protein synthesis possibly resulting from an inhibited supply of C. Total oxidizable C, soluble sugar content and C/N ratios were lower in mycorrhizal plants, suggesting that the mycorrhizal fungi were competing with the host for photosynthetically-derived C, consequently causing growth depressions. A possible mechanism of this competition is discussed.
Endogone spores and wheat roots were recovered from soil by wet sieving. Spore numbers changed little from December to June, greatly increased in July, and began to decrease in September. Formalin applied in 1967 decreased the number of spores present in 1968, more in soil not previously given formalin than in soil given formalin in 1964 and 1965. Plots without nitrogen and other fertilizers consistently contained more spores than plots with fertilizers. Vesicular-arbuscular mycorrhizal infection was sparse in May and increased during the summer to a peak in September. It was most abundant in plots containing most Endogone spores. Four spore types occurred in one Rothamsted wheat field, but only one type was found in a nearby wheat field. The increases in spore numbers and mycorrhizal infection during the summer suggest that Endogone has little effect on wheat during the spring period of rapid root and shoot development before flowering.
TRIGLYCERIDE-rich lipoprotein particles, in particular the very low density lipoproteins (VLDL), are important secretory products of the liver1. In the study of the formation and release of these particles, progress has been made by the demonstration that VLDL can be visualized by electron microscopy as electron-opaque particles, diameter 300-1000 Å (ref. 2). This makes it possible to follow the time sequence of their intracellular migration from their site of formation to that of their release into the extracellular space. Although there is evidence that final discharge of these particles into the space of Disse occurs through fusion of the membrane of the vacuoles which contain lipoproteins, with the plasma membrane2, the mechanisms governing the intracellular translocation of the VLDL particles are still unknown. Circumstantial evidence has led to the suggestion that microtubules and microfilaments are part of a contractile system of the cell which plays an important role in the secretory processes of several different cell types3-9. To investigate the possibility that microtubules are also involved in the secretion of lipoprotein particles by the liver, we made use of the mitotic-spindle inhibitors, vincristine and colchicine, agents which interact with these structures and interfere, probably selectively, with their function10-13. Using this approach, we report here a marked decrease in triglyceride-rich lipoprotein particle release by livers perfused in the presence of mitotic-spindle inhibitors.
Eight clay pots (5x8 inches) were filled with a 2:1 mixture of beach sand and clay soil and autoclaved. The mixture was then inoculated with chlamydospores of the endomycorrhizal fungus, Endogone mosseae (Nicol.&Gerd.) obtained from pot cultures previously established with Festuca occidentalis (Hook).
Mycorrhizal soybean (Glycine max L. Merr. var. Harosoy-63) plants have lower resistances to water transport than nonmy-corrhizal plants after 4.5 weeks of growth. Although resistances of whole plants differ by 40%, there were no differences in the resistances of stems plus leaves, indicating that the major effect of the mycorrhizae was to reduce the resistance of the roots. Since the fungitoxicant, p-chloronitrobenzene, had no effect on resistances to water transport, reduced resistances were probably not caused by a direct modification of the transport pathway by the fungus. Differences in resistance between mycorrhizal and nonmycorrhizal soybean were essentialy eliminated by the application of nutrients to the soil. Thus, lowered resistances of mycorrhizal roots growing in soil with low levels of nutrients probably resulted from the enhanced nutrient status of the plant brought about by the fungus. Mycorrhizal infection increased growth at both low and high nutrient levels.
Competition of the nonmycotrophic weed Salsola kali with vesicular-arbuscular mycorrhizal perennial grasses
- E B Allen
- M F Allen
- M G Boosalis
- E B Allen
- M F Allen
- M G Boosalis
Root-microfungal associations in a shortgrass prairie In: The Belowground Ecosystem : A Synthesis of Plant-associated Processes
- D E Davidson
- M Christensen
- D E Davidson
- M Christensen
Methods of studying plant water relations. Ecological Studies Czechoslovak Academy of Sciences
- B Slavik
Competition of the nonmycotrophic weedSalsola kaliwith vesicular-arbuscular mycorrhizal perennial grasses
- E B Allen
- M F Allen