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Abiotic factors modulating the soil and rhizosphere microbiome. See text for details.
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Microbial soil communities are active players in the biogeochemical cycles, impacting soil fertility and interacting with aboveground organisms. Although soil microbial diversity has been studied in good detail, the factors that modulate its structure are still relatively unclear, especially the environmental factors. Several abiotic elements may p...
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... this ecological perspective, Wardle (2006) reviewed the influence of several sources of biotic origin on soil microbial diversity, including plant species, interactions between organisms within and beyond the rhizosphere, and animal and human activities. In the present review, we focus on the influence of abiotic factors on the diversity of soil microbes, especially those inhabiting the rhizosphere, that may be relevant to plant development, including type of soil, pH, temperature, and geographical and other environmental characteristics ( Figure 1). ...
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Soil is an excellent niche for the growth of microorganisms which includes plant growth-promoting rhizobacteria (PGPRs). PGPRs have great potential for plant growth promotion as they control pest and disease and have been considered important in sustainable agriculture. PGPRs induce and/or synthesize various growth-promoting and biocontrolling chem...
Both the plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGR) exert beneficial effects on plant growth even under stress, but combined effect of both of them has not been evaluated yet. Present investigation was aimed to determine the responses of 2 chickpea varieties (differing in drought tolerance) to 3 PGPR viz. Bacillus...
Nitrogen-fixing plant growth-promoting rhizobacteria collectively known as rhizobia have been extensively investigated due to their exceptional quality to establish functional symbiosis with legumes. As a result of this incredible interaction, they supply nitrogen to plants, which is one of the major nutrient elements. Rhizobia are capable of colon...
Citations
... Other abiotic factors included drought, heavy metals, and salt. Because of abiotic or biotic stress, these factors can modulate the assembly of microbial communities associated with the plant, including endophytes (Santoyo et al. 2017). Likewise, endophytic microbial populations or communities present in seeds may have important impacts across generations. ...
Plants have microbial companions inhabiting a hidden world within their tissues that play relevant roles in their environmental fitness. Some of these beneficial microorganisms can colonize seeds by exerting a functional echo in future generations. In this study, we review the most recent advances in microbial endophytes residing in seeds and their ecological functions, including the reproductive stage, from germination to adulthood. Similar to free-living plant growth-promoting microorganisms, microbial endophytes, whether bacteria or fungi, exhibit similar direct (e.g., facilitation of resources and regulation of phytohormones) and indirect (e.g., antibiosis and induced systemic resistance) action mechanisms, which are also analyzed. Finally, some agro-biotechnological applications of microbial endophytes and their advantages of being inherited through seeds are discussed, such as facilitating their field application and ensuring that their beneficial actions increase crop health and sustainable production.
... Microorganisms that are good for plants naturally live in. They take part in several soil activities that impact productivity, crop yields, and general plant health [113]. Many attempts have been undertaken to investigate the diversity, distribution, and behavior of indigenous soil microorganisms in soil habitats to understand how microbial inoculants function and how they affect soil health [114]. ...
The necessity for efficient mitigation techniques is highlighted by the worldwide loss in plant output caused by biotic and abiotic stressors. Promising bioinoculants known as Plant Growth-Promoting Rhizobacteria (PGPR) have been shown to provide improved nutritional availability, hormone regulation, and stress relief, among other advantages. Through several mechanisms such as phytohormone synthesis and ACC deaminase activity, they combat many environmental stressors such as pests, diseases, temperature variations, heavy metals, salt, and drought. Current research emphasizes the function of PGPR in a number of tree species, such as Quercus suber, Haloxylon ammodendron, and Acacia gerrardii. For example, inoculating Acacia gerrardii with Bacillus subtilis causes notable alterations in gene expression, indicating possible benefits in salinity and drought tolerance. Furthermore, in some nurseries, Quercus suber seedling quality is improved by a blend of bacterial inoculum and ECM fungus. Additionally, PGPR show effectiveness against heavy metal toxicity and heat stress. Sustainable plant growth depends on utilizing stress-resistant PGPR strains and maximizing microbial diversity. While breeding and genetic engineering provide long-term fixes, microbial inoculation offers a quick and affordable substitute. Moreover, PGPR promote environmental sustainability by improving soil fertility through processes including nitrogen fixation and phosphorus solubilization. In order to enhance plant development that is environmentally sustainable and optimize PGPR-mediated stress tolerance, it is essential to conduct multidisciplinary research and field investigations.
... In agricultural ecosystems, microbial community diversity is mainly driven by agricultural practices, environmental conditions, soil type, and plant species. In contrast, in natural ecosystems, biotic interactions, plant species, and plant diversity mainly modulate microbial communities (Santoyo et al., 2017). ...
In this study, we investigated the bacterial diversity and plant growth‐promoting (PGP) properties of bulk soil bacteria of Vachellia tortilis subsp. raddiana collected from the Taidalt and Amazloug nature preserves area in southern Morocco. Using repetitive extragenic palindromic polymerase chain reaction fingerprinting and 16S rDNA sequencing, 93 strains were identified. They belonged mainly to the genera Bacillus and Peribacillus. In vitro tests for PGP traits showed high levels of activity for strains belonging to the genera Bacillus and Pseudomonas. It was relevant that several Bacillus strains produced auxin (maximum amount 262.61 µg mL⁻¹ for Bacillus sp. LMR1097), solubilized phosphate (maximum amount 22.10 µg mL⁻¹), or produced siderophores, while three strains were able to fix atmospheric nitrogen (LMR1145, LMR1013, and LMR1015). Inoculation of V. tortilis subsp. raddiana plants with selected bacterial strains (LMR881 and LMR1097) increased shoot and root growth parameters. The strain Pantoea sp. LMR881 had the highest mean values for shoot and root length (24.60–14.80 cm) and shoot dry weight (1.31 g), whereas Bacillus sp. LMR1097 showed the lowest mean shoot dry weight. Overall, these results highlight the potential of using selected native bacterial inoculants for improving growth of candidate tree plants to be used in restoration programs of arid degraded areas.
... Bacteria must navigate the heterogeneous environment that the rhizosphere provides, with variations in nutrient availability, pH, oxidative stress, and osmotic conditions at the microscale level [34,35]. Mutation of several regulatory genes responsible for sensing and adapting to environmental stimuli were observed to hinder growth in the rhizosphere and colonization of all five plant species. ...
Bacterial persistence in the rhizosphere and colonisation of root niches are critical for the establishment of many beneficial plant-bacteria interactions including those between Rhizobium leguminosarum and its host legumes. Despite this, most studies on R. leguminosarum have focused on its symbiotic lifestyle as an endosymbiont in root nodules. Here, we use random barcode transposon sequencing (RB-TnSeq) to assay gene contributions of R. leguminosarum during competitive growth in the rhizosphere and colonisation of various plant species. This facilitated the identification of 189 genes commonly required for growth in diverse plant rhizospheres, mutation of 111 of which also affected subsequent root colonisation (rhizosphere progressive), and a further 119 genes necessary for colonisation. Common determinants reveal a need to synthesise essential compounds (amino acids, ribonucleotides, and cofactors), adapt metabolic function, respond to external stimuli, and withstand various stresses (such as changes in osmolarity). Additionally, chemotaxis and flagella-mediated motility are prerequisites for root colonisation. Many genes showed plant-specific dependencies highlighting significant adaptation to different plant species. This work provides a greater understanding of factors promoting rhizosphere fitness and root colonisation in plant-beneficial bacteria, facilitating their exploitation for agricultural benefit.
... The initial years are the most critical for establishing tree species because seedlings are vulnerable to resource constraints, such as drought, salt, low soil fertility, pests and diseases, and pollution (Askari-Khorasgani and Pessarakli, 2019). In addition, climate change and global warming exacerbate the impact of environmental stresses on plants (Santoyo et al., 2017). Plant growth morphology, growth physiology, gene expression, and cellular metabolism are all affected by drought stress (Farooq et al., 2009). ...
Drought due to climate change or reduced precipitation is one of the main factors limiting the growth and establishment of plants and is one of the most critical challenges facing humans. To investigate the effect of different levels of drought stress on some pine species, this research was carried out as a factorial experiment using two factors and a completely randomized design. It included five populations of four pine species (Pinus brutia Ten. var. eldarica, P. nigra Arnold, P. mugo, and P. banksiana Lamb (including populations 8310055 and 8960049), and three levels of irrigation (100%, 75%, or 50% FC, denoted as normal, mild or intense drought stress, respectively) with three replicates. The findings showed that, photosynthetic pigments, relative water content, visual quality, the content of nutrients, protein content, and fresh and dry weight all decreased significantly when plants were exposed to intense drought stress. However, raised proline levels, electrolyte leakage percentage, soluble sugars levels, and antioxidant enzyme activity. We detected a decline in most growth traits when comparing mild drought stress conditions to normal irrigation, yet acceptable quality seedlings when compared to intense drought stress. Intense drought stress had a substantial impact on many pine seedlings. PCA results showed that among different pine species, the level of resistance to drought is as follows: P. mugo> P. brutia var. eldarica> P. nigra> P. banksiana 8310055> P. banksiana 8960049. Our novel finding was that, P. mugo is a resistant species in arid and semi-arid regions, and P. banksiana species, especially its population of 8960049, is sensitive.
... Soil can directly provide the necessary environmental conditions for the survival of microorganisms (Santoyo et al., 2017). Organic fertilizer application can not only increase the total amount of soil nutrients such as soil total organic carbon, total nitrogen, and total phosphorus but can also increase the content of available soil nutrients (alkali nitrogen, available phosphorus, available potassium) Qaswar et al., 2020). ...
Introduction
The soil microbial community plays an important role in modulating cotton soil fertility. However, the effects of chemical fertilizer combined with organic fertilizer on soil chemical properties, microbial community structure, and crop yield and quality in arid areas are still unclear. This study aimed to explore the effects of different organic fertilizers on soil microbial community structure and diversity and cotton growth and yield.
Methods
High-throughput sequencing was used to study the soil bacteria and fungi in different growth stages of cotton. The field fertilization experiment had five treatments.
Results
The results indicated that the treatments of chemical fertilizer reduction combined with organic fertilizer significantly increased soil available nitrogen and phosphorus in cotton field. There were significant differences in the abundance of the bacterial and fungal communities in the dominant phyla among the treatments. At the phyla level, there were not significantly different in the diversity of bacteria and fungi among treatments. There were significant differences in the composition and diversity of bacterial and fungal communities during the entire cotton growth period ( p = 0.001). The rhizosphere bacterial and fungal community structure was significantly affected by soil TK, NH 4 ⁺ , AK, TP, AN, and NO 3 ⁻ . The different fertilization treatments strongly influenced the modular structure of the soil bacterial and fungal community co-occurrence network. A reduction in chemical fertilizer combined with organic fertilizer significantly improved cotton stem diameter and seed yield, and the effect of the biological organic fertilizer on plant growth and yield formation was greater than that of ordinary organic fertilizer.
Discussion
This study provide a scientific and technical basis for the establishment of environmentally friendly green fertilization technology for cotton in arid areas and the promotion of sustainable development of cotton industry.
... The variety of species and functional groupings in soil determines its multifunctionality (6). Soil ecosystems comprise intricate connections between living things with their surroundings (7). They are distinguished by the diversity of their vegetation, interactions between biotic and abiotic processes, and climatic and soil conditions. ...
The concept of a circular bioeconomy focuses on the sustainable use of
biological resources, minimizing waste and negative environmental impacts.
Soil ecosystem services are crucial in this context as they support agricultural
production, biodiversity conservation, and nutrient recycling. The circular
bioeconomy offers benefits like resource efficiency, reduced waste, lower
environmental impacts, and economic opportunities, with soil ecosystem
services playing a significant role in achieving these benefits. Soil provides
various services for human well-being, including security, protection from
ecological shocks, access to balanced diets, clean water, clean air, and energy
for temperature control. This review highlights the importance of soil ecosystem
services in circular resource management and bio-based sustainable production
systems. These services encompass provisioning, regulating, cultural, and
supporting roles, providing resources like food, fibre, and fuel, controlling
erosion and temperature, offering aesthetic value, and sustaining plant and
animal diversity. The bioeconomy comprises knowledge, research, technology,
and innovation related to biological resource production, use, conservation, and
regeneration. The application of circular bioeconomy strategies benefits from
the ecological services soil provides to bio-based industries. The policy that
converts farming, grazing, and woodland systems into renewable operations is
bound to protect soil functions while relieving pressure on other critical
ecosystem functions. Overall, a holistic understanding of soil ecosystem
services is crucial for successfully implementing circular practices across
different bioeconomy sectors. Soil conservation, sustainable management, and
the protection of soil resources are vital for maintaining the services that support
a circular bioeconomy
... obtained from the same teosinte seeds inhibited fungal growth and mycotoxin production and maintained a potential to combat phytopathogens (Mousa et al., 2015). Currently, an important research topic is to elucidate how much of a plant's phenotype, adaptive capacities, evolution, and productivity are due to its endospheric and rhizospheric microbiome (Santoyo et al., 2017;Kaur et al., 2021). ...
The bacterial component of plant holobiont maintains valuable interactions that contribute to plants’ growth, adaptation, stress tolerance, and antagonism to some phytopathogens. Teosinte is the grass plant recognized as the progenitor of modern maize, domesticated by pre-Hispanic civilizations around 9,000 years ago. Three teosinte species are recognized: Zea diploperennis, Zea perennis, and Zea mays. In this work, the bacterial diversity of three species of Mexican teosinte seeds was explored by massive sequencing of 16S rRNA amplicons. Streptomyces, Acinetobacter, Olivibacter, Erwinia, Bacillus, Pseudomonas, Cellvibrio, Achromobacter, Devosia, Lysobacter, Sphingopyxis, Stenotrophomonas, Ochrobactrum, Delftia, Lactobacillus, among others, were the bacterial genera mainly represented. The bacterial alpha diversity in the seeds of Z. diploperennis was the highest, while the alpha diversity in Z. mays subsp. mexicana race was the lowest observed among the species and races. The Mexican teosintes analyzed had a core bacteriome of 38 bacterial genera, including several recognized plant growth promoters or fungal biocontrol agents such as Agrobacterium, Burkholderia, Erwinia, Lactobacillus, Ochrobactrum, Paenibacillus, Pseudomonas, Sphingomonas, Streptomyces, among other. Metabolic inference analysis by PICRUSt2 of bacterial genera showed several pathways related to plant growth promotion (PGP), biological control, and environmental adaptation. The implications of these findings are far-reaching, as they highlight the existence of an exceptional bacterial germplasm reservoir teeming with potential plant growth promotion bacteria (PGPB). This reserve holds the key to cultivating innovative bioinoculants and formidable fungal antagonistic strains, thereby paving the way for a more sustainable and eco-friendly approach to agriculture. Embracing these novel NGS-based techniques and understanding the profound impact of the vertical transference of microorganisms from seeds could revolutionize the future of agriculture and develop a new era of symbiotic harmony between plants and microbes.
... Numerous studies have shown that abiotic stresses like drought, extreme soil salinity, and human activities, which reduce soil fertility and increase the extent of saline in agricultural soil, cause an increase in the salt composition of soils worldwide, which reduces plant growth, health, and production, are highly detrimental to plant growth and agricultural productivity. 5,6 Salts can enter the soil through natural processes or human actions like irrigation with unfit water. According to reports, one of the major abiotic elements is salt, which seriously impacts plant growth and food production, particularly in soil with high salinity levels that are often simple to detect using the electrical conductivity method. ...
... Moreover, the bacterial counts and types were affected by both abiotic and biotic factors such as soil temperature, humidity, type, salinity, pH, composition, and fertility. 6 These factors played more significant roles in transforming the soil microbiota, which forms varied interactions and relationships with plants and increases growth, development, production, and protection against fungal and bacterial pathogens. In addition, the soil microbiota played a significant role in minerals, agricultural and organic waste cycles, and soil fertility degradation. ...
... These actions include lengthening roots and aerial structures through the production of enzymes, antibiotics, and plant growth regulators, as well as growth under various stress conditions due to the ability of the vegetative cells to sporulate. 6 For many years, authors have claimed that the genus Bacillus is magical and that its species are ideal candidates for possessing a wide range of biological functions with advantageous processes and serve as important bio-inoculants, bio-stimulants, biofertilizers, or biocontrol agents. In the field and under salt stress conditions, to combat adverse conditions like salt, drought, and nutrient deficiency, Bacillus cells are successfully used as soil inoculums. ...
Every minute, the world’s population grows, and in order to feed them, crop output and agricultural productivity must be improved by adding crucial microorganisms that boost plant yields in various ways through nitrogen fixation, the secretion of both plant growth regulators and 1-aminocyclopropane 1-carboxylate deaminase, as well as some antimicrobial agents. Numerous endophytic bacteria have recently been used to increase plant yields, and agricultural production in addition to reducing salt stresses. Many scientists have made an effort to clarify and comprehend the processes by which bacteria promote plant growth and production. A vital substance known as 1-aminocyclopropane-1-carboxylate (ACC) deaminase is produced by several bacteria, plants, and fungi to decrease ethylene levels in a plant grown under different environmental stress. The gaseous hormone ethylene (C2H4) is synthesized in plant tissues from the precursor ACC, and it has numerous biochemical roles in plants, such as cells differentiation and tissue development, seedling, root hair, leaf, and flower growth and development in addition to fruit ripening and formation of anthocyanin and volatile compounds. Thus, this critical enzyme had influential roles in plants during their positive interaction with bacteria which increase plant growth due to auxin production and protect plants against different environmental stress like drought, high salts, wilting, high level of heavy metals, contaminants with pesticides, and microbial pathogen infections. Different bacterial genera are highly ACC deaminase-producer, and these bacteria support plant growth and agricultural process. In conclusion, bacteria can replace chemicals in a variety of environmentally benign methods to boost soil fertility and plant productivity. However, much research is required to determine the efficacy of these bacteria before suggesting their use on a broad scale in the field.
... Some evidence points to the absence of such a relationship at both small (Cordier et al., 2012;Oono et al., 2017) and large scales (Vincent et al., 2016;Barge et al., 2019;U'Ren et al., 2019), while other studies show evidence of distance decay, especially for rare foliar fungal endophyte taxa (Vaz et al., 2014;David et al., 2016;Koide et al., 2017;Oono et al., 2017). Climate, a major factor driving the community composition of plants, seems to have less influence on determining the composition of fungal endophytes, particularly at fine scales (Compant et al., 2010;Santoyo et al., 2017). Water availability in particular affects some fungal endophytes' ability to germinate and persist (Arnold, 2007;Peay et al., 2016). ...
