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Chitin‐supplemented Foliar Application of Serratia marcescens GPS 5 Improves Control of Late Leaf Spot Disease of Groundnut by Activating Defence‐related Enzymes
Abstract
Chitinolytic Serratia marcescens GPS 5 and non-chitinolytic Pseudomonas aeruginosa GSE 18, with and without supplementation of chitin, were tested for their ability to activate defence-related enzymes in groundnut leaves. Thirty-day-old groundnut (cv. TMV 2) plants pretreated with GPS 5 and GSE 18 (with and without supplementation of 1% colloidal chitin) were challenge inoculated after 24 h with Phaeoisariopsis personata, the causal agent of late leaf spot (LLS) disease of groundnut. GPS 5 and GSE 18, applied as a prophylactic spray, reduced the lesion frequency by 23% and 67%, respectively, compared with control. Chitin supplementation had no effect on the control of LLS by GSE 18, unlike GPS 5, which upon chitin supplementation reduced the lesion frequency by 64%, compared with chitin alone. In a time course study the activities of chitinase, β-1,3-glucanase, peroxidase and phenylalanine ammonia lyase were determined for the different treatments. There was an enhanced activity of the four defence-related enzymes with all the bacterial treatments when compared with phosphate buffer and colloidal chitin-treated controls. In correlation to disease severity in bacterial treatments, chitin-supplemented GSE 18 was similar to GSE 18, whereas chitin-supplemented GPS 5 was much more effective than GPS 5, in activation of the defence-related enzymes. The high levels of enzyme activities following chitin-supplemented GPS 5 application continued up to the measured 13 days after pathogen inoculation.
... CHOS with a degree of polymerization (DP) 4-10 were active elicitors and induced peroxidase activity and lignification in wheat (Triticum aestivum L.) leaves (Vander et al., 1998). In line with these results, chitin-supplemented application of B. circulans GRS243 and S. marcescens GPS5 also improved biological control of late leaf spot disease (LLS) (Kishore et al., 2005) by activating the defenserelated enzymes, chitinase, b-1,3-glucanase, peroxidase, and phenylalanine ammonia lyase. It was also shown that the CHOS with a DP P 5 act as potent phytoalexin elicitors (Okada, 2002) and can induce oxidative burst (Madhuprakash et al., 2015c) in suspension-cultured rice cells. ...
... Among which, chitinase-D from S. proteamaculans was known to be the best bacterial transglycosidase followed by ChiA and ChiB of S. marcescens (Zakariassen et al., 2011). It was also reported that the purified chitinase of S. marcescens GPS5 inhibited the germination of Phaeoisariopsis personata conidia by lysis and effectively controlled LLS (Kishore et al., 2005). ...
... S. marcescens GPS5 was originally isolated from phyllosphere of groundnut plant which was chitinolytic and promoted plant growth (Kishore et al., 2005). ...
The current study describes heterologous expression and biochemical characterization of single-modular chitinase-D from Serratia marcescens (SmChiD) with unprecedented catalytic properties which include chitobiase and transglycosylation (TG) activities besides hydrolytic activity. Without accessory domains, SmChiD, hydrolyzed insoluble polymeric chitin substrates like colloidal, α- and β-chitin. Activity studies on CHOS with degree of polymerization (DP) 2–6 as substrate revealed that SmChiD hydrolyzed DP2 with a chitobiase activity and showed TG activity on CHOS with DP3–6, producing longer chain CHOS. But, the TG products were further hydrolyzed to shorter chain CHOS with DP1–2 products. SmChiD with its unique catalytic properties, could be a potential enzyme for the production of long chain CHOS and also for the preparation of efficient enzyme cocktails for chitin degradation.
... The beneficial effect of chitin-based treatments to antagonistic bacteria is not restricted to B. subtilis, with both chitin and chitosan improving the control of Fusarium wilt in both tomato [66] and cucumber [67] when applied to the soil with a range of different species of chitinolytic microbes. Kishore et al. [68] found that chitin addition improved the control of Phaeoisariopsis personata, the causal agent of late leaf blight in peanut, by the bacterium Serratia marcescens. In addition to direct antibiosis, the study by Kishore et al. [68] found that these applications also increased the activity of key plant defense enzymes. ...
... Kishore et al. [68] found that chitin addition improved the control of Phaeoisariopsis personata, the causal agent of late leaf blight in peanut, by the bacterium Serratia marcescens. In addition to direct antibiosis, the study by Kishore et al. [68] found that these applications also increased the activity of key plant defense enzymes. ...
... A range of pathogen-related (PR) proteins have also been found to be activated after chitin-based treatments have been applied to plants. Most notably this includes chitinases, but also includes glucanases [68] peroxidases, polyphenoloxidases [124] and MAP-kinases [132]. Protease inhibitors are also produced [118]; presumably to limit the activity of the pathogen's own enzymes involved in attack. ...
In recent decades, a greater knowledge of chitin chemistry, and the increased availability of chitin-containing waste materials from the seafood industry, have led to the testing and development of chitin-containing products for a wide variety of applications in the agriculture industry. A number of modes of action have been proposed for how chitin and its derivatives can improve crop yield. In addition to direct effects on plant nutrition and plant growth stimulation, chitin-derived products have also been shown to be toxic to plant pests and pathogens, induce plant defenses and stimulate the growth and activity of beneficial microbes. A repeating theme of the published studies is that chitin-based treatments augment and amplify the action of beneficial chitinolytic microbes. This article reviews the evidence for claims that chitin-based products can improve crop yields and the current understanding of the modes of action with a focus on plant-microbe interactions.
... The results revealed that different plant colonization pattern and different mechanism of disease suppression elicited by S. marcescens might have offered greater protection to the plants against the anthracnose disease. S. marcescens effectively controlled the late leaf spot in groundnut (Krishna Kishore et al., 1999) [8] . Someya et al. (2000) [19] recorded reduced damping-off incidence with S. marcescens under greenhouse conditions. ...
... The results revealed that different plant colonization pattern and different mechanism of disease suppression elicited by S. marcescens might have offered greater protection to the plants against the anthracnose disease. S. marcescens effectively controlled the late leaf spot in groundnut (Krishna Kishore et al., 1999) [8] . Someya et al. (2000) [19] recorded reduced damping-off incidence with S. marcescens under greenhouse conditions. ...
... Bacterial Bio control agents had colonized 95 per cent of the lettuce roots by 4 days after radicle emergence. Kishore et al., (1998) reported that foliar application of bacterial bio inoculants improved control of late leaf spot disease of ground nut by activating defense relating enzymes. Ragavan (2003) reported that foliar application of antagonistic bacteria (Pseudomonas fluorescens) was highly effective managing the rice blast disease. ...
... Weller (1984) isolated Pseudomonas fluorescens from the entire length of wheat root, maximum near seed and root tip. In case of groundnut S. marcescens move in roots, coleoptile and the first and second leaves (Kishore et al., 1998). The safe storage period of three months for maintaining the viability of bacterial antagonists in talc formulations. ...
... Frankowskii et al. [39] have purified two chitinolytic enzymes CHIT60 and CHIT100 from S. plymuthica HRO-C48 and both the enzyme inhibited spore germination and germ tube elongation of the phytopathogenic fungus Botrytis cinerea. Exogenous addition of chitin in foliar sprays was found to increase the efficiency of chitinolytic Serratia marcescens GPS5 in controlling late leaf spot of groundnut caused by Phaeoisariopsis personata [40]. Mehmood et al. [36] characterized a 60 kDa chitinase from Serratia proteamaculans 18A1 which demonstrated the antifungal activity against the pathogenic fungi Fusarium oxysporum and Aspergillus niger. ...
... Someya et al. [42] have revealed the ability of S. marcescens strain B2 to manage rice blast through increased production of Lipoxygenase (LOX) after bacterial inoculations. The chitin amendment with the S. marcescens GPS5 culture was also found to have increased production of defense related genes such as beta 1, 3-glucanase, peroxidase and phenylalanine ammonia lyase [40]. S. plymuthica R1GC4 was also reported to modulate induced systemic resistance in cucumber against Pythium ultimum. ...
Plant diseases generate substantial threat to agriculture. Bacterial species with the ability to prevent these diseases are expected to have promises as natural alternative to chemical control measures. The bacteria of the genus Serratiahave been reported to have bothrhizospheric and endophytic association with protective effect to various plants. Among the various species, S. marcescens, S. plymuthica, S. rubidaea and S. liquefaciens have been extensively studied for their anti-phytopathogenic mechanisms. These involve production of antibiotics such as prodiogisin, pyrrolnitrin and oomycidin and also the production of lytic enzymes such as chitinases. In addition to this, they are also known for their ability for the induction of induced systemic resistance, which indirectly make the plant competent towards various pathogens. Serratia spp. are also known for their accumulation of other plant beneficial features like indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and phosphate solubilization. Hence the multi-beneficial mechanisms of Serratia spp. towards plants is highly impressive and is expected to have increasing agricultural applications. Current review is designed to provide insight into plant beneficial promises of Serratia spp.
... Scope of the chitinolytic microorganisms in management of phytopathogenic fungi has grown as chitin and crude fungal cell wall-supplemented applications were observed to increase the attainable levels of disease protection ( Bell et al. 1998). The rationale of using chitin with chitinolytic isolates is a logic approach because bacterial isolates multiply and increase in their numbers by using chitin as a carbon source; meanwhile the chitinase produced inhibits the fungal pathogen growth at the rhizosphere ( Kokalis-Burelle et al. 1992;Kishore et al. 2005;Hariprasad et al. 2011). Also, isolates of Bacillus circulans, B. subtilis, and Serratia marcescens that have been pre-induced for chitinase production by multiplication in chitin-supplemented peat formulations showed enhanced disease control activities in the rhizosphere and phylloplane of groundnut ( Manjula and Podile 2001;Kishore et al. 2005). ...
... The rationale of using chitin with chitinolytic isolates is a logic approach because bacterial isolates multiply and increase in their numbers by using chitin as a carbon source; meanwhile the chitinase produced inhibits the fungal pathogen growth at the rhizosphere ( Kokalis-Burelle et al. 1992;Kishore et al. 2005;Hariprasad et al. 2011). Also, isolates of Bacillus circulans, B. subtilis, and Serratia marcescens that have been pre-induced for chitinase production by multiplication in chitin-supplemented peat formulations showed enhanced disease control activities in the rhizosphere and phylloplane of groundnut ( Manjula and Podile 2001;Kishore et al. 2005). On the other hand, β-1,3-glucanase produced by PGPR is reported to degrade β-1,3-glucan a major cell wall constituent of oomycetes which is evidenced by the studies of Fridlender et al. (1993), where β-1,3glucanase producing strain of Pseudomonas cepacia inhibited the rhizosphere proliferation of various soil-borne phytopathogens. ...
In the present scenario increased agricultural productivity is achieved by indiscriminate and excessive application of agrochemicals which lead to health and environmental hazards. Extensive research in developing eco-friendly strategy to reduce or replace the application of agrochemicals revealed plant growth-promoting rhizobacteria (PGPR) as potential candidate. PGPR are an important group of bacterial communities residing in rhizosphere and exert beneficial effects on host plant through various mechanisms. The mode of action through which PGPR enhance plant fitness under different biotic and abiotic stress have been a target of research from several years. Hence, in this chapter, mechanism involved in PGPR-mediated growth promotion and suppression of biotic and abiotic stress in plants is reviewed. PGPR is known to exert its beneficial effect on plant through several mechanisms. Plant growth-promoting mechanisms include root colonization, nitrogen fixation, phosphate solubilization, production of IAA, and other phytohormones, siderophore, and volatiles. Suppression of biotic stress is through competition for space, food and nutrition with phytopathogens, production of antibiotic, siderophores, volatiles, and by inducing systemic resistance (ISR). Abiotic stress (especially drought and salt) management by means of PGPR involves modification of physiological and biochemical activities of host plant by producing abscisic acid and other phytohormones, lowering the ethylene by activity of ACC deaminase, and producing antioxidants, which are collectively termed as induced systemic tolerance (IST). Hence expression of these PGPR traits and factors affecting on it should be studied thoroughly in order to use it to its best. Under experimental or field conditions, these traits may express singly or simultaneously which is affected by various biotic and abiotic factors which alter the performance of introduced PGPR.
... For example, chitin is an excellent carbon and nitrogen source for many chitinolytic Streptomyces strains (Robbins et al. 1998). The application of a BC agent along with chitin has great importance in plant disease management (Kishore et al. 2005). Recently, CC (1 %) supplemented Trichoderma/Hypocrea spp. ...
... In conclusion, our results showed that the antagonistic activity of a marine S. vinaceusdrappus was directly enhanced by CC and thus had potential in reducing the tomato root rot disease. Kishore et al. (2005) also reported that supplementation of Bacillus circulans GRS 243 and Serratia marcescens GPS5 with 1 % colloidal chitin in the greenhouse reduced lesion frequency of late leaf spot of groundnut caused by Phaeoisariopsis personata by 60 %, when compared with application of bacterial cells alone. Yu et al. (2008) also discussed similar kind of effect by amendment of colloidal chitin with Cryptococcus laurentii against Penicillium expansum in pear fruit. ...
A chitinolytic actinomycete Streptomyces vinaceusdrappus S5MW2 was isolated from water sample of Chilika lake, India and identified using 16S rRNA gene sequencing. It showed in vitro antifungal activity against the sclerotia producing pathogen Rhizoctonia solani in a dual culture assay and by chitinase enzyme production in a chitin supplemented minimal broth. Moreover, isolate S5MW2 was further characterized for biocontrol (BC) and plant growth promoting features in a greenhouse experiment with or without colloidal chitin (CC). Results of greenhouse experiment showed that CC supplementation with S5MW2 showed a significant growth of tomato plants and superior disease reduction as compared to untreated control and without CC treated plants. Moreover, higher accumulation of chitinase also recovered in the CC supplemented plants. Significant effect of CC also concurred with the Analysis of Variance of greenhouse parameters. These results show that the a marine antagonist S5MW2 has BC efficiency against R. solani and chitinase enzyme played important role in plant resistance.
... Scope of the chitinolytic microorganisms in management of phytopathogenic fungi has grown as chitin and crude fungal cell wall-supplemented applications were observed to increase the attainable levels of disease protection ( Bell et al. 1998). The rationale of using chitin with chitinolytic isolates is a logic approach because bacterial isolates multiply and increase in their numbers by using chitin as a carbon source; meanwhile the chitinase produced inhibits the fungal pathogen growth at the rhizosphere ( Kokalis-Burelle et al. 1992;Kishore et al. 2005;Hariprasad et al. 2011). Also, isolates of Bacillus circulans, B. subtilis, and Serratia marcescens that have been pre-induced for chitinase production by multiplication in chitin-supplemented peat formulations showed enhanced disease control activities in the rhizosphere and phylloplane of groundnut ( Manjula and Podile 2001;Kishore et al. 2005). ...
... The rationale of using chitin with chitinolytic isolates is a logic approach because bacterial isolates multiply and increase in their numbers by using chitin as a carbon source; meanwhile the chitinase produced inhibits the fungal pathogen growth at the rhizosphere ( Kokalis-Burelle et al. 1992;Kishore et al. 2005;Hariprasad et al. 2011). Also, isolates of Bacillus circulans, B. subtilis, and Serratia marcescens that have been pre-induced for chitinase production by multiplication in chitin-supplemented peat formulations showed enhanced disease control activities in the rhizosphere and phylloplane of groundnut ( Manjula and Podile 2001;Kishore et al. 2005). On the other hand, β-1,3-glucanase produced by PGPR is reported to degrade β-1,3-glucan a major cell wall constituent of oomycetes which is evidenced by the studies of Fridlender et al. (1993), where β-1,3glucanase producing strain of Pseudomonas cepacia inhibited the rhizosphere proliferation of various soil-borne phytopathogens. ...
... Therefore, both direct antifungal effects and induced resistance were involved in chitosan-based plant protection. In some cases, chitin was applied along with chitinolytic biocontrol agents to induce immunity in plants, increasing the efficiency of biocontrol agents under field conditions (Kishore et al., 2005b;Manjula & Podile, 2001). Chitinolytic biocontrol agents utilize chitin as a carbon source by secreting extracellular chitinases resulting in rapid and prolonged establishment of biocontrol agents in the rhizosphere or phylloplane depending on their mode of application. ...
... Therefore, it is conceivable that chitin acts both as a major source of carbon for chitinolytic biocontrol agents and also induces defense in plants due to production of chitin oligomers. Enhanced activity of defense-related enzymes was observed in the foliar application of chitin-supplemented Serratia marcescens (Kishore et al., 2005b). Seed application of chitin along with Bacillus subtilis AF1 improved resistance against collar rot disease in groundnut and Fusarium wilt in pigeonpea (Manjula & Podile, 2001). ...
Abstract Plants have evolved mechanisms to recognize a wide range of pathogen-derived molecules and to express induced resistance against pathogen attack. Exploitation of induced resistance, by application of novel bioactive elicitors, is an attractive alternative for crop protection. Chitooligosaccharide (COS) elicitors, released during plant fungal interactions, induce plant defenses upon recognition. Detailed analyses of structure/function relationships of bioactive chitosans as well as recent progress towards understanding the mechanism of COS sensing in plants through the identification and characterization of their cognate receptors have generated fresh impetus for approaches that would induce innate immunity in plants. These progresses combined with the application of chitin/chitosan/COS in disease management are reviewed here. In considering the field application of COS, however, efficient and large-scale production of desired COS is a challenging task. The available methods, including chemical or enzymatic hydrolysis and chemical or biotechnological synthesis to produce COS, are also reviewed.
... Many studies have been documented the beneficial effects of certain rhizobial strains in improving growth of legumes as well as non-legumes. Inoculation of Rhizobium in consortium with free-living rhizospheric bacteria has also given excellent results in enhancing crop growth and productivity [18,19]. These PGPRs can be used effectively to meet the nutrient -deficient conditions and their use can be favourable to reduce the use of chemical fertilizers and support of environment friendly crop productivity [20]. ...
The present investigations on the studies to see the effect of seed biopriming with bacterial consortia in green gram were conducted in a field experiment employing randomized block design with nine treatments and three replications during kharif season 2022-2023 at the Post Graduate Institute, research farm of the Department of Plant Pathology and Agricultural Microbiology, Mahatma Phule Krishi Vidyapeeth, Rahuri, Dist. Ahmednagar, Maharashtra. The result revealed that, among the treatment, T4 recorded the highest average plant height (65.66 cm) and average number of leaves (22.79 plant-1), average number of branches (5.23), average number of pods (30.93), average grain yield (9.18 q ha-1), average stalk yield (24.25 q ha-1) and 1000 seed weight i.e. test weight (33.78 g).
... However, under field conditions, treatments with a single biocontrol agent or biostimulant are often not sufficient to ensure an effective crop protection (Monte, 2001;Kishore et al., 2005), which may also be the case when both are applied in combination. Shukla et al. (2021) showed that neither Trichoderma nor chitosan were effective in pathogen control when used as single treatments and concluded that the addition of a reduced copper rate may sufficiently support the effect of the tested agents. ...
... Furthermore, the maximum amount of calcium was observed in the CNF/protein/CaCO3 treatment in both Entisols and Andosols, suggesting that the added CaCO3 was decomposed and absorbed by the plant. Furthermore, according to Kishore, Pande, and Podile (2005) and Egusa et al. (2019), the application of CNF materials increases plants' self-protection function against diseases and pests. It has also been inferred that CNF is degraded by chitinase in the plant and acts as an elicitor inducer, contributing to plant growth promotion (Erwig et al., 2017). ...
Large numbers of crab shells are disposed of as food waste in the food processing process. Chitin nanofiber (CNF) refers to chitin extracted from crab shells in the form of ultrafine fibers that enable uniform dispersion in water. We explored the feasibility of using CNF materials as plant growth promoters. We investigated the effects of CNF application with fertilizer and its various application methods on the growth of the komatsuna plant cultivated in Entisols and Andosols with the application of CNF materials. The surface application of CNF materials had plant growth-promoting effects in both Entisols and Andosols. The topdressing treatment was more effective in promoting plant growth in Entisols. The inorganic nitrogen content absorbed by plants in the topdressing treatment was lower than that in the basal application treatments because the CNF added during the latter half of the cultivation period was not fully decomposed before the completion of cultivation. The calcium content of plants in the basal application treatment of CNF/protein/calcium carbonate was higher than that in the topdressing treatments, indicating that the calcium encasing the CNF was absorbed by the plants. The cultivation of plants with the application of CNF materials promoted nitrogen utilization efficiency and plant growth.
... There are, however, references on biological control of LLS due to prophylactic foliar application of several bacterial strains. For example Bacillus circulans GRS 243 and Serratia marcescens GPS 5 supplemented with colloidal chitin (Kishore et al. 2005a), Pseudomonas aeruginosa GSE 18 and S. marcescens GPS 5, mainly attributed to the enhanced activity of several defense-related enzymes (Kishore et al. 2005b), and P. aeruginosa GSE 18 and GSE 19 in combination with reduced doses of the fungicide chlorothalonil (Kishore et al. 2005c). Also, Anil and Podile (2012) found that foliar application of B. thuringiensis SFC24, tolerant to chlorothalonil, reduced the LLS severity due to its chitinolytic activity. ...
Trichoderma harzianum ITEM 3636 has been tested against different soil-borne peanut diseases, applied as a seed treatment. The strain protected mature peanut plants suggesting a long lasting protection, and was isolated from plant roots several months after the sowing in field assays. We hypothesized that T. harzianum ITEM 3636 colonizes peanut roots as an endophyte as was demonstrated with other few strains, and in this interaction, the fungi reside in plant roots and can protect the plant against a foliar disease. The spreadability of conidia on the surface of peanut seeds and the mycelial growth inside root tissues were studied through scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), respectively. Conidia from ITEM 3636 had an appropriate distribution on coated seed surfaces. Furthermore, the fungal mycelium colonized root surfaces forming appressorium-like structures and swollen cells. The overlay of green and red confocal images clearly showed fungal hyphae grew internally through epidermal and cortical cells. Once inside the root, T. harzianum ITEM 3636 increased the levels of jasmonic acid in roots but not of salicylic acid. Also, the effect of seed treatment in peanut plant defense against Nothopassalora personata was evaluated under greenhouse conditions. ITEM 3636 significantly decreased the number of affected leaflets, late leaf spot (LLS) incidence and severity, and induced higher levels of defense related enzymes in leaflets after challenge with the pathogen. No direct activation of JA or SA pathways was observed in the leaves of Trichoderma-induced peanuts plants. T. harzianum decreased the concentration of ABA, which may reflect that the strain might improve defense mechanisms of the plant, through ABA content.
... The plant beneficial organisms can produce various hydrolytic enzymes such as cellulase, proteases, chitinase, and glucanase which can cause the destruction of the cells of these pathogenic fungi, insects, etc. The PGPRs Serratia marcescens GPS 5 and Pseudomonas aeruginosa GSE 18 produced the CAZymes chitinase along with β-1,3-glucanase, peroxidase, and the enzyme phenylalanine ammonia lyase which significantly reduced the lesion formation by the peanut pathogen Phaeoisariopsis personata (Kishore et al. 2005). Another approach would be competitive inhibition of pathogens, whereby these organisms can occupy the niches and nutrients essential for pathogen growth (Kamilova et al. 2005). ...
As the world population is growing exponentially, there is enormous pressure on land resources to ensure food security. The exploitation of forest areas for agricultural purposes can have serious environmental consequences. Microbes, which are an integral part of the soil environment, play an important role in increasing the yield of crops. Their activities play a central role in the soil environment, influencing soil properties and thereby affecting the quality and quantity of agricultural products. They have found their application in biocontrol of pests and insects, increasing soil fertility and promoting plant growth. In the food industry, they are important in the processing and preservation of food. In addition, the protein-rich microbial cells are cultivated as food supplements. Microbes are thus important for the improvement and sustainability of agriculture and food production.KeywordsMicroorganismBiofertilizersBiocontrolFood processingPreservation
... Chitin + urea amendments in soil enhanced plant nutrition by improved soil microbiota, thereby controlling microbial pathogens in tomato and carnation (Belair and Trumblay, 1995). Chitin has also been used to enhance the efficiency of natural biological controls agents because of the enhanced production of chitinases in presence of chitins and some of its derivatives (Kishore et al., 2005). There reports on post-harvest disease management and antiviral properties (Iriti et al., 2006) of chitin and its derivatives. ...
Aspergillus niger was found to be predominantly
associated with Aspergillus rot of pomegranate in
orchard as well as after harvest and storage but in
storage Aspergillus niger cause severe damage due
to favorable conditions. Therefore, Three fungicides,
two antifungal agent and three plant extracts were
evaluated for their efficacy against both isolate of
Aspergillus nigerin vitro and one contact fungicide
(mancozeb), two antifungal agent and three botanicals
were used in fruit dip treatment. Mancozeb at 0.5, 1.0
and 1.5 per cent inhibited the maximum mycelial
growth of both the isolates as 100 per cent at all three
concentrations followed by chlorine water that caused
100 per cent inhibition at 4 per cent and 6 percent
concentration while boric acid least effective and the
botanical extracts of neem oil and ginger (rhizome
extract) at 4 and 6 per cent concentration were
effective in vitro while garlic extract was lest effective
compare with neem oil and ginger extacts. When
evaluated by fruit dip method for injured inoculated
fruits under laboratory condition, Mancozeb at all
three concentration and chlorine water at 6%
concentration were effective in reducing fruit rot
followed by boric acid. The botanical extracts (neem
oil and ginger) were effective against A. niger in fruit
dip treatment at 4 and 6 per cent concentration,
respectively.
... It has been shown in earlier studies that fluorescent pseudomonads could be isolated from aerial parts of plants grown from seeds treated with the bacteria (Colyer and Mount, 1984;Mew and Rosales, 1986) [4,10] . In case of groundnut S. marcescens moved in roots, coleoptiles and the first and second leaves (Kishore et al., 1998). Similarly, the systemic movement of P. fluorescens occurred in emerging roots and shoots of rice plants grown from seeds treated with P. fluorescens (Ragavan, 2003;Shyamala and Sivakumar, 2012) [13,14] . ...
Fluorescent Pseudomonads belong to plant Growth Promoting Rhizobacteria (PGPR), the important group of bacteria that play a major role in the plant growth promotion, induced systemic resistance, biological control of pathogens etc. Many strains of Pseudomonas fluorescens are known to enhance plant growth promotion and reduce severity of various diseases. The aim of this investigation was to assess the systemic movement and phylloplane survival of P. fluorescens (PF9) in rice crop after treated with PF9 as seed treatment and foliar spray @ 10ml/kg and 0.5% concentration respectively under green house condition. The results clearly revealed that systemic movement of bacterium (PF9) could be recovered in roots up to 75 days (3.8×10 3) the maximum period tested, where as in stem and leaves the population declined with increase in the sampling period and the bacterium could be recovered only up to 60 days after sowing the seeds treated with bacterium. Maximum population of the test bacterium could be detected in root (6.8×10 3), stem (5.6×10 3) and leaves (4.1×10 3) at 15 days after sowing indicated the necessity for subsequent application of the antagonist. Also, the population of bacterium in the phylloplane and leaf tissues after foliar spray showed a declining trend with increase in the sampling period. The maximum population (18.2×10 3) on phylloplane and population in leaf tissue (4.9×10 3) was recorded on the first day after foliar spray and then the population showed a gradual decline and reached the minimum population in the phylloplane (0.6×10 2) and in the leaf tissues (0.3×10 3) at 12 days after spraying.
... employ different mechanisms to inhibit this fungal pathogen (Shafi et al., 2017). Examples of such are nutrient antagonism (Kamilova et al. 2005), antifungal lipopeptides production (Hazarika et al., 2019), and lytic enzyme production such as chitinases that can prevent fungal hyphal extension by cell wall degradation (Kishore et al. 2005). ...
Maize is an essential cereal crop and the third most essential food crop globally. The extensive dependence on pesticides and chemical fertilizers to control pests and increase crop yield, respectively, has generated an injurious impact on soil and animal health. Plant growth-promoting rhizobacteria (PGPR), which depict a broad array of bacteria inhabiting the root vicinity and root surface, have proven to be a better alternative. These organisms expressly or by implication foster the growth and development of plants by producing and secreting numerous regulatory compounds in the rhizosphere. Some rhizobacteria found to be in association with Zea mays rhizosphere include Bacillus sp., Azotobacter chroococcum, Burkholderia spp., Streptomyces spp., Pseudomonas spp., Paenibacillus spp., and Sphingobium spp. For this review, the mechanism of action of these rhizospheric bacteria was grouped into three, which are bioremediation, biofertilization, and biocontrol.
Graphical abstract
Key points
• Plant–microbe interaction is vital for ecosystem functioning.
• PGPR can produce volatile cues to deter ravaging insects from plants.
... An increase in chitinolytic microbial populations and a signicant reduction in the incidence of fungal diseases were recorded by amending soil with chitin (Bell et al. 1998). Chitin supplementation also found to support the survival of Bacillus cereus and B. circulans in the groundnut phylloplane and resulted in better control of early and late leaf spot disease (Kishore et al. 2005). ...
... Such formulations control soil-borne diseases, such as damping-off and root-knot caused by nematodes (Ha et al. 2014;Rajkumar et al. 2008), and foliar plant diseases (Kim et al. 2008;Kim et al. 2010;Kishore and Pande 2007;Kishore et al. 2005a, b;Seo et al. 2007). Application of microbial cultures grown in a chitin-supplemented medium containing cells, metabolites, and the remaining growth substrates increases the survival and multiplication of chitinolytic bacteria introduced onto plant surfaces (Kishore et al. 2005a) and activates defense-related enzymes in the treated plants (Kishore et al. 2005b). An array of extracellular lytic enzymes, including chitinase, protease, and lipase, as well as antimicrobial compounds including lipopeptides, pyrrolnitrin, and violacein are present in the cell-free supernatants (CFS) obtained from the cultures of Gram-negative chitinolytic biocontrol bacteria (Kamil et al. 2018;Kim et al. 2017a). ...
The chitinase-producing bacterium, Paenibacillus elgii HOA73, is a biocontrol agent that limits the damage caused to plants by microbial pathogens, insects, and nematodes. However, the mechanisms involved in the biocontrol of plant diseases by HOA73 have not been determined. The objective of this study was to elucidate the role of extracellular chitinase obtained from isolate HOA73 in the control of the fungal pathogen Botrytis cinerea, the causative agent of gray mold in tomato. The HOA73 strain grew efficiently in a chitin-containing broth and produced chitin oligomers through chitinase activity; protease, lipase, and Fe-chelating siderophores were also secreted by the bacterium. Cultures containing intact bacteria inhibited B. cinerea conidia germination to a greater extent than did the bacterial cells alone or the cell-free culture supernatant. The antifungal activity increased with culture age and was heat-sensitive because of chitinase-mediated production of long-chain chitin oligomers. The biocontrol efficacy of undiluted bacterial cultures against gray mold in tomato was comparable to that of a standard fungicide. This study demonstrated that P. elgii HOA73 bacterial cultures grown on chitin-based minimal medium may be an effective formulation for the integrated control of gray mold.
... In addition, it also increased the populations of indigenous chitinolytic epiphytes (Kokalis-Burelle et al., 1992) and plant growth promotion as well (Manjula Table 1 Examples of chitinolytic bacteria and associated chitinases with pesticidal activity. Broadway et al., 1998 and Podile, 2001) by activating defense related enzymes (Kishore et al., 2005b;Ge et al., 2010). Some studies also reported an improved activity of chitinolytic bacteria when cultured in chitin supplemented media (El-Tarabily et al., 2000;Ajit et al., 2006). ...
Chitin metabolism is an essential life sustaining activity of phytophagous insects, phytopathogenic fungi and parasitic nematode which are the major limiting factors of agricultural production systems. Diverse bacteria, although non-chitinous life forms, are reported to degrade native chitin associated with the pestiferous organisms thereby exerting pathogenicity. So, the deployment of chitinolytic bacteria, associated genes and enzymes for plant protection against invading parasites and insect pests is well studied. Currently, worldwide research mainly focuses on finding novel strains and enzymes with potential implications in pest management. Owing to the effectiveness and synergistic potential, the putative chitinases and chitinolytic bacteria are formulated as biocontrol agents for direct application, utilized in the development of transgenics and supplemented with other pesticidal toxins. This fast progressing twig of pest management has the ability to replace hazardous chemical pesticides, if not so, can reduce their dosage. The present review critically discusses the available diversity of chitinolytic bacteria and the present status of pest management achieved through this approach. The possible levels of control and achievable synergism against major pest species are also presented in the context of latest research findings to understand subsistence pest management using bacterial chitinases.
... PCR 조건은 최종농도 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 1.5 mM MgCl 2 , 200 nM dNTPs, 10 pmol의 ITS 8F와 ITS 1492R 프라이머, 0.1 unit 의 rTaq DNA polymerase (Takara, Japan)를 사용하였으며, (Lee, 2012;Thomashow and Weller, 1996). 식물병 방제를 위하여 키틴분해 능력을 지닌 생물적 방제인자를 적용하는 기술은 매우 중요한 것으로 보고되어 있다 (Cho et al., 2007;Han et al., 2012;Kim et al., 2007;Kishore et al., 2005;Michael et al., 1992;Pati et al., 2011;Yandiferi et al., 2015). ...
The purpose of this study was to estimate the chitinolytic and antifungal activity of Actinomycetes sp.isolated from waste mushroom media. In five kinds of waste mushroom media, Sinyeong mushroom and Yangsongi were the order of the population density of actinomycetes. Totally 91 chitinolytic isolates of Actinomycetes sp. were obtained from waste mushroom media. The isolates were categorized into 3 groups based on chitinolytic activity and antagonisms against Phytophthora capsici, Rhizoctonia solani, Sclerotinia sclerotiorum, Collectotrichum gloeosporioides, and Cladosporium cucumerinum in vitro. CA-23 was selected as a representative isolate of a group showing strong chitinolytic and antagonistic activities to all of the plant pathogens, while AA-65 was selected as a representative isolate showing no chitinolytic activities but strong antagonistic activities to the pathogens. CA-23 and AA-65 were highly effective on control of Phytophthora blight of hot-pepper, powdery mildew and scab of cucumber in a greenhouse tests. Among the isolates tested, CA-23 showed highest control efficacy, while AA-65 not only effectively controlled the diseases but also consistently increased plant growth and yield. Although the isolates are similarly affected on suppression of plant pathogens, the isolates could be differ from each other in modes of action. Further studies on mechanisms and practical applications are being progressed.
... 8.3. Besides nitrogen-fixing rhizobia, several authors observed that other associated beneficial bacteria exert over this group of plants multiple plant-promoting activities such as phosphate-solubilizing activity, IAA production, and biocontrol properties (siderophore production, antibiosis, etc.) (Pal et al. 2000;Deshwal et al. 2003;Dey et al. 2004;Kishore et al. 2005;Taurian et al. 2008Taurian et al. , 2010Ibañez et al. 2009;Tonelli et al. 2010). ...
The rhizosphere and the phylloplane of plants are habitats for large number of microorganisms. The study of plant-associated bacteria is important not only for understanding their role in these interactions but also for biotechnological application in areas as the plant growth promotion. Legume plants are able to form nitrogen-fixing nodules by symbiotic association with soil bacteria collectively known as rhizobia. Even when the term “root nodule bacteria” has been exclusively applied to rhizobia, nonsymbiotic endophytic bacteria from several genera have been isolated from legume nodules, and this is the main topic of this chapter. Endophytes are defined as those microorganisms isolated and detected inside the tissues by microscopic methods, which maintain their ability to infect plants, being rhizobia the most studied group. Endophytic bacteria can positively influence plant growth through different mechanisms, such as fixation of atmospheric nitrogen, solubilization of phosphates, and protection against pathogens, among others. Therefore, a wide number of studies have been and still are focused in plant-growth-promoting bacteria as potential supplements of fertilizers, herbicides, fungicides, etc. For endophytes to exert beneficial effects on plant growth, they should be in an intimate relationship with the host plant. The signaling cascade involved in legume–rhizobia interaction that leads to nodule development as well as recent knowledge about the taxonomy of this bacterial group are also described.
... The application of chitosan in agriculture is recently becoming a major focus of research. Research has shown that chitosan and its derivatives can be used as plant growth regulators, fungicides, and seed coating agents [6]. Chitosan and its derivatives, such as glycolchitosan and carboxymethylchitosan, are known to form a semi-permeable film around plant tissues. ...
Induction of resistance to downy mildew caused by Plasmopara halstedii in sunflower was studied after treatment with chitosan. Treatment of sunflower seeds with 5% chitosan resulted in decreased disease severity and offered 46 and 52% protection under greenhouse and field conditions respectively. The induction of resistance to P. halstedii by chitosan was accompanied by the accumulation of various host defense-related enzymes in susceptible sunflower seedlings. Enhanced activation of catalase (CAT) and phenylalanine ammonia lyase (PAL) was observed at 6 h and 9 h post-inoculation respectively, while peroxidase (POX), polyphenol oxidase (PPO) and chitinase (CHI) levels were high at 12 h post-inoculation in sunflower seedlings raised from seeds treated with chitosan. Northern hybridization analysis revealed increased levels of transcripts for five known defense response genes viz., Pr-1a, b-1,3-glucanase, chi-tinase, peroxidase and chalcone synthase in these seedlings. This enhanced and early activation of defense-related responses in the susceptible cultivar Morden treated with chitosan was comparable to that in the resistant cultivar. The results indicate that chitosan induced resistance against P. halstedii in sunflower is mediated through the enhanced expression of genes for defense-related proteins.
... P. elgii [12] was isolated from chitin/chitosan-rich soils of a mushroom production firm, S. M. Agritech Pvt. Ltd., Hyderabad, India. S. marcescens [16] and S. maltophilia (K279A) are from our culture collection in Department of Plant Sciences, University of Hyderabad. B. cereus (MTCC 430) that promoted the growth of tobacco, was used to bacterize the seeds of four different plants including groundnut, tobacco, tomato and pigeonpea. ...
The outcome of an interaction between plant growth promoting rhizobacteria and plants may depend on the chemical composition of root exudates (REs). We report the colonization of tobacco, and not groundnut, roots by a non-rhizospheric Bacillus cereus (MTCC 430). There was a differential alteration in the cell wall components of B. cereus in response to the REs from tobacco and groundnut. Attenuated total reflectance infrared spectroscopy revealed a split in amide I region of B. cereus cells exposed to tobacco-root exudates (TRE), compared to those exposed to groundnut-root exudates (GRE). In addition, changes in exopolysaccharides and lipid-packing were observed in B. cereus grown in TRE-amended minimal media that were not detectable in GRE-amended media. Cell-wall proteome analyses revealed upregulation of oxidative stress-related alkyl hydroperoxide reductase, and DNA-protecting protein chain (Dlp-2), in response to GRE and TRE, respectively. Metabolism-related enzymes like 2-amino-3-ketobutyrate coenzyme A ligase and 2-methylcitrate dehydratase and a 60 kDa chaperonin were up-regulated in response to TRE and GRE. In response to B. cereus, the plant roots altered their exudate-chemodiversity with respect to carbohydrates, organic acids, alkanes, and polyols. TRE-induced changes in surface components of B. cereus may contribute to successful root colonization and subsequent plant growth promotion.
... For enumeration of S. entomophila AB2, serially diluted suspensions were plated onto caprylate thallous agar (CTA) medium (O'Callaghan et al., 2002) supplemented with antibiotic Ampicillin (A). The colony count was taken against the UV lamp (Kishore et al., 2005). ...
Serratia entomophila, a Gram negative non spore forming bacteria, is commercially exploited as biocontrol agent of pasture pest, grass grub (Costelytra zealandica, Coleoptera) in New Zealand as soil inoculants. As an exception, the strain S. entomophila AB2 used in this study is having insecticidal property against pod borer (Heliothis armigera, Lepidoptera), a phyllospheric pest. Expermental results showed high rate of mortality when the pests were fed with shoot portion of ground nut developed from bacteria treated seeds. Antifungal property of S. entomophila AB2 was recorded when tested in vivo using different parts of plant developed from bacteria treated and untreated seeds. In the present study, the systemic infestation was understood by isolation and enumeration of the inoculant from different plant tissues in specific medium and an increment in number within the tissues was also observed. This is the first report of systemic spreading of S. entomophila in plant parts to provide protection against insect and fungal pests.
... There is a significant difference between control and 13-1, 7-1, 7-4, 7-6, 15-1, 11-3 resistant plant progenies, respectively (P≤0. 05) In previous studies reported by Kishore et al. 2005, chitin supplemented foliar application of Serratia marcescens GPSS5 controlled late leaf spot disease of peanut and reduced the lesion frequency by only 64 %. In the present studies, it was evident that in transgenic plants, lesion frequency was decreased significantly to about 97.1 % compared to the respective non-transformed WT plants. ...
Peanut (Arachis hypogaea L.) is the sixth most important oil seed crop in the world. Yield loss due to Cercospora leaf spot (early and late leaf spots) is a serious problem in cultivating this crop. Non-availability of resistant genes within crossable germplasms of peanut necessitates the use of a genetic engineering strategy to develop genetic resistance against various biotic stresses. The pathogenesis-related (PR) proteins are a group of plant proteins that are toxic to invading fungal pathogens, but are present in trace amounts in plants. The PR proteins, PR-5 and defensins, are potent antifungal proteins. A double gene construct with SniOLP (Solanum nigrum osmotin-like protein) and Rs-AFP2 (Raphanus sativus antifungal protein-2) genes under separate constitutive 35S promoters was used to transform peanut plants. Transgenic peanut plants expressing the SniOLP and Rs-AFP2 genes showed enhanced disease resistance to late leaf spot based on a reduction in number and size of lesions on leaves and delay in the onset of Phaeoisariopsis personata leaf spot disease. PCR, RT-PCR, and Southern hybridization analyses confirmed stable integration and expression of these genes in peanut transgenics. The results demonstrate the potential of SniOLP and Rs-AFP2 genes in developing late leaf spot disease resistance in transgenic peanut.
... The highest enzymatic activity in terms of fold count was observed in GG-20, TG-26 and J-11 varieties and least in TPG-41 variety in FCF-treated plants than MCWtreated plants. These results are in agreement with the reports on induction of systemic resistance in groundnut by foliar applications of biocontrol agent ⁄ elicitors (Sathiyabama and Balasubramanian 1998;Meena et al. 2000;Kishore et al. 2005a). ...
Plants evolve a strategy to survive the attacks of potential pathogens by inducing the microbial signal molecules. In this study, plant defence responses were induced in four different varieties of Arachis hypogaea (J-11, GG-20, TG-26 and TPG41) using the fungal components of Sclerotium rolfsii in the form of fungal culture filtrate (FCF) and mycelial cell wall (MCW), and the levels of defence-related signal molecule salicylic acid (SA), marker enzymes such as peroxidase (POX), phenylalanine ammonia lyase (PAL), β-1,3-glucanase and lignin were determined. There was a substantial fold increase in POX, PAL, SA, β-1,3-glucanase and lignin content in FCF- and MCW-treated plants of all varieties of groundnut when compared to that of control plants. The enzyme activities were much higher in FCF-treated plants than in MCW-treated plants. The increase in fold activity of enzymes and signal molecule varied between different varieties. These results indicate that the use of fungal components (FCF and MCW) had successfully induced systemic resistance in the four different varieties of groundnut plants against Sclerotium rolfsii.
... Similarly, a reduction in shoot length at 14 DAS in Mon# 2-17(C − ) could be due to its deleterious effect on seedlings. Supplementing with chitin has been reported to enhance biocontrol ability of B. subtilis AF1 (Kishore et al. 2005). However, in this study, chitin supplement did not have a profound effect on growth promotion ability of the strains. ...
Jatropha (Jatropha curcas L.) is a non-edible oil-seed plant with adaptability to marginal semi-arid lands and wastelands. The Indian Government is
promoting jatropha to reduce dependence on the crude oil and to achieve energy independence by the year 2012, under the National
Biodiesel Mission. Selected strains of Bacillus spp., either supplemented with or without chitin, were tested for their ability to promote growth of jatropha seedlings in
pot culture studies. The strains supported growth of jatropha seedlings up to 42days after sowing. Among all strains, Bacillus pumilus (IM-3) supplemented with chitin showed over all plant growth promotion effect resulting in enhanced shoot length (113%),
dry shoot mass (360%), dry root mass (467%), dry total plant mass (346%), leaf area (256%), and chlorophyll content (74%)
over control. Treating seeds with strain IM-3 without chitin resulted in enhanced dry shoot mass (473%), dry total plant mass
(407%), and chlorophyll content (82%). However, Bacillus polymyxa (KRU-22) with chitin supported maximum root length (143%). Either strain IM-3 alone or in combination with other promising
strains could be promoted further for enhanced initial seedling growth of jatropha.
Chitin, a widely available natural polymer, is the fundamental structural component of crustacean shells. The crustacean processing industry produces a lot of shell waste each year
(in millions), most of which is discarded and poses serious environmental problems. This waste can be effectively utilized to produce chitin and chitin nanomaterials with superior physicochemical and biological properties, making it applicable in various industries. In this context, this review outlined the chitin extraction methods from crustacean shell waste. The recent advancements in chitin nanomaterial isolation in the form of chitin nanocrystals (ChNCs) and chitin nanofibers (ChNFs) from purified chitin are discussed. Furthermore, the current practical applications of chitin and chitin nanomaterials in agriculture, biomedicine, and the food industry are reviewed to better understand the polymer’s applicability for future research and development.
Chitin is an insoluble structural polysaccharide present in the exoskeleton of insects. One potential biopesticide is enzyme chitinase, which degrades chitin-soluble and insoluble oligosaccharides. Recently, chitinase enzymes as a biopesticide are developing to control insect and fungal pests—an alternative approach with enzyme-based biopesticides to avoid the chemical pesticides against pests and pathogens. The success in exploring chitinase from microbial sources, especially for agriculture, has a high volume low cost, and it also depends on the availability and active formulation of the product at a reasonable cost. The roles of chitinolytic enzymes as a biocontrol agent, different mechanisms to mass culture the chitinase and the formulations, and making the enzyme stable for the long term is the wide area to research. The chitin degradation, and identification of chitinase from different microbial sources with varying specificities, may make them more useful in commercial processes soon. In this chapter, Pseudomonas sp.-derived chitinase enzymes, essential in the agricultural field, benefit the plant by PGPR activity and mass multiplications of bacteria and the enzyme, production, and formulations in low cost, requirements to register the biopesticide and marketing were discussed in this chapter.KeywordsPseudomonas speciesMass productionFormulationShelf-lifeCommercializationBio-control agent
Powdered crab and lobster shells (crustacean meal) obtained from fisheries are used as soil amendments to promote plant health and defense. In this study, a commercial crustacean meal amendment used to promote the health of lettuce, tomato, and other crop plants was applied to roots of lettuce and tomato seedlings. Gene expression profiling of the treated roots was assessed by RNA sequencing (RNA-seq) at 24 h after application relative to a 0 h time point. The RNA-seq analyses revealed upregulation of different types of genes in both tomato and lettuce roots at 24 h. Gene ontology analyses revealed increased expression of genes associated with oxidoreductases/metal ion binding in tomato roots at 24 h, while there was predominantly increased expression of genes associated with cell wall organization, lyases, and hydrolases in lettuce roots at 24 h. The types of defense-related genes expressed were also markedly different. In tomato roots, the most highly induced gene (log 2 fold change 13.84, P ≤ 0.001) encoded a defense-associated miraculin-like protein, but transcripts of a similar gene were not induced in lettuce roots. Interestingly, phenylpropanoid pathway genes relating to cell wall biogenesis and lignification were significantly upregulated in both lettuce and tomato roots, suggesting that strengthening of plant cell walls is a common response to crustacean meal application. This research provides insight into gene expression patterns in the roots of lettuce and tomato in response to crustacean meal, improving our understanding of how this amendment could aid in plant health.
[Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022.
The chitosan (CHT) biopolymer is a de-acetylated chitin derivative that exists in the outer shell of shrimp, shellfish, lobster or crabs, as well as fungal cell walls. Because of its biodegradability, environmental non-toxicity, and biocompatibility, it is an ideal resource for sustainable agriculture. The CHT emerged as a promising agent used as a plant growth promoter and also as an antimicrobial agent. It induces plant growth by influencing plant physiological processes like nutrient uptake, cell division, cell elongation, enzymatic activation and synthesis of protein that can eventually lead to increased yield. It also acts as a catalyst to inhibit the growth of plant pathogens, and alter plant defense responses by triggering multiple useful metabolic pathways. This review emphasizes the role and mechanisms of CHT as a plant growth promoter and disease suppressor, and its future implications in agriculture.
In vitro selection of Withania somnifera has been incurred against Alternaria alternata by selection pressure of fungal toxin in an innovative way. Solid green callus was maintained in Murashige and Skoog’s medium supplemented with 6-Benzylaminopurine (2 mgL-1). Toxin was partially purified from A. alternata broth culture. Elite clone was generated by gradual intoxication of solid green callus in the toxin containing medium (5–400 mgL-1). Three highest dose of toxin tolerance was selected viz. 50 mgL-1, 100 mgL-1 and 200 mgL-1. Plants were successfully regenerated from those toxin selected callus. Eventually, various defense enzymes and total phenolics were measured in regenerated plants and toxin selected callus. Callus selected from 100 mgL-1 toxin dose and plants obtained from them give the best results among all and showed more than 2–5 fold increase of
defense enzyme activities and total phenolics compared to control. Furthermore, those plants when challenge inoculated showed significant reduction (more than 70%) of leaf spot incidence. Augmentation of disease resistance persists for at least two successive generations. Furthermore, the increase in defense molecules also correlated with increased nitric oxide generation (73%). Presence of withaferin A and withanolide A has also been confirmed in the toxin regenerated plants by High-performance thin-layer chromatography (HPTLC) analysis. Over all observations suggests that fungal toxin at a concentration 100 mgL-1 and by habituation technique can be use as a selection method for the production of disease resistant medicinally important crop like W. somnifera without altering its secondary metabolite production.
Plant growth promoting rhizobacteria (PGPR) are extensively used as biofertilizers to improve the soil nutrition for a variety of crop plants. The plant-PGPR interaction, with special reference to chemical signalling molecules is not understood clearly, unlike other beneficial plant-microbe interactions. Chemo-attraction of a PGPR from soil microbial pool towards a plant could be dependent on some of the molecules in the plant root exudates (REs), similar to the beneficial association of legume-rhizobia. In this study, a few functional properties of PGPR like growth, chemotaxis, and biofilm formation by two PGPR strains viz., Bacillus sonorensis RS4 and Pseudomonas aeruginosa RP2 were assessed in the presence of groundnut REs. Functional properties of both the strains were significantly influenced by the REs in a strain-dependent manner. Metabolite profiling of the REs from PGPR-bacterized (RS4 or RP2) and non-bacterized seedlings was performed with GC-MS/MS after 12 and 24 days of growth. A total of 75 metabolites were detected in groundnut REs. Threonine and glyoxylic oxime acid were detected in RP2-bacterized REs, while serine, pentanoic acid, glucopyranoside, tartaric acid, and 2-pyrrolidinone were detected in REs of seedlings bacterized with RP2 and RS4. The results suggested that the PGPR induced distinct variations in the REs. Identification of the interaction-specific metabolites will be useful to develop effective PGPR based bio-formulations for better PGPR colonization and improving crop yields.
Selection and application of rhizobacteria, for improved plant health will benefit from a complete understanding of the plant–bacteria interaction. Root exudates (REs) are known to contain signal molecules that facilitate beneficial association of plants with microbes. We have selected a tentatively identified Pseudomonas sp. (RP2), from 126 groundnut (Arachis hypogaea L.)-associated bacterial isolates that significantly promoted growth of groundnut and also induced resistance against the stem rot pathogen Sclerotium rolfsii. REs were collected from 12 to 24 days grown RP2-bacterized and non-bacterized plants and analyzed through gas chromatography coupled with mass spectrometer. Several organic acids, fatty acids, sugars, hydrocarbons, and alcohols were detected. In the untargeted multivariate analysis of the REs, relative content of eight compounds varied significantly on RP2 bacterization. Among these eight compounds, myristic acid, stearic acid, and palmitic acid, positively influenced the root colonization by RP2. Benzoic acid and salicylic acid, increased in RP2-bacterized REs, showed the highest growth inhibition of S. rolfsii. In root proteomics, 11 differentially expressed proteins were identified by 2D-gel electrophoresis followed by matrix-assisted laser desorption ionization-time of flight. Chitinase, thaumatin-like protein, ascorbate peroxidase, and glutathione S-transferase, known to have a role in plant defense against phytopathogens, were upregulated in RP2 interaction. Similarly, upregulation of enolase in roots is likely to improve plant growth in RP2-bacterized groundnut. We conclude that colonization of groundnut roots by RP2 resulted in exudation of metabolites that facilitated root colonization, suppressed fungal growth, promoted plant growth, and also increased the expression of defense-related proteins in the roots.
Recent worldwide demand for organic and sustainable agriculture products is driving the development of formulations of biopesticides effective in the field. Biopesticides have the benefit of environmentally-friendly qualities. However, biocontrol approaches largely have been ineffective in controlling plant pests in field conditions. Previously, we developed a cost-effective biocontrol formulation containing chitin and chitinase-producing biocontrol bacteria with field efficacy. This formulated product has successfully suppressed various plant diseases in the field conditions. In this review, we focus on ecological aspects and the potential mechanisms underpinning the success of chitinase-producing bacteria. In addition, we discuss the possibility on-site cultivation of the formulated products to further strengthen the approach as being farmer friendly and successful.
Mycophagy should not be considered as a single and homogeneous category of nutritional biology due to the specific symbiotic chitinolytic bacteria associated with mites and fungi. To test interaction among mites, fungi, and chitinolytic bacteria, experiments were conducted on the model species Tyrophagus putrescentiae (Schrank). Mucor sp, Alternaria alternata, Penicillium claviforme, P. griseofulvum, and Verticillium sp. were plated onto malt agar and offered to T. putrescentiae in the laboratory. Mites were evaluated utilizing microanatomical examination based on histology, excrement analysis using fluorescence microscopy, bacterial plating, impact of mite homogenate on fungi in Petri dishes, reproduction of mites feeding upon each fungus, and isolation of associated bacteria inside mites. There were clear differences regarding the digested spores of different fungi passing through the gut and subsequently in the feces. Abundances of bacterial cells in excrement also corresponded to the fungi offered. The extracts from mites had chitinolytic activity, and the plated bacteria are known to produce exochitinases. The various feeding patterns observed were caused by differences in the cell wall structures of the tested fungi. The study illustrates that mycophagy in saprophagous mites does not consist of a single pattern, but rather that it can be classified into several sub-patterns depending upon the digested fungal species and its parts. The results point to a nearly symbiotic relationship between chitinolytic bacteria and digested fungi in mycophagous microarthropods.
Thirty six rhizobacterial isolates belonging to genus Serratia were isolated from 57 rhizospheric soil samples of different tomato (Lycopersicon esculentum Mill.) growing regions of Karnataka. Among them, 29 isolates were found colonizing the roots of tomato seedlings under in vitro conditions. When these root colonizing isolates were analyzed for their plant growth promoting ability only 18 isolates were found promoting the plant growth and remaining 11 isolates were found inhibiting the plant growth. These selected isolates were also able to produce IAA, ACC deaminase, chitinase, ß-1,3-glucanase, solubilize phosphate, HCN and were resistant to multiple antibiotics. Involvement of specific plant growth promoting rhizobacteria (PGPR) traits of these isolates involved in plant growth promotion and disease suppression were studied under laboratory and greenhouse conditions. All the selected isolates showed varied degrees of increase in plant growth over control. Isolate Pan-9/c and Bag-6/a reduced the Fusarium wilt incidence significantly, but none of the isolate reduced the early blight incidence, a foliar disease of tomato. Talcum powder formulation of isolate Pan-9/e survived till the end of the experimental period (120 days) where the population decreased to 1.4 × 107 cfu/g talc powder. Application of formulations as a seed treatment increased the plant growth parameters and yield, and suppressed the Fusarium wilt under greenhouse conditions. The ability of Serratia to improve plant health, and its possible use in sustainable tomato production is discussed.
Chitin is a major structural component of fungi and exoskeleton of insects, crustaceans and other arthropods. It is an insoluble, unbranched, linear chain of β-1, 4-linked N-acetyl D-glucosamine residues and is the second most abundant renewable carbohydrate polymer in nature after cellulose and first in marine environment. The annual production of chitin in aquatic biosphere is around 1011 ton. Chitinases produced by chitinolytic bacteria have the potential to convert this waste to pharmaceutically valuable end products such as N-acetyl glucosamine and chitooligosaccharides, and are viable alternatives of chemical processes currently used for the purpose. Chitinases from different bacteria, fungi, plants and animals are glycosyl hydrolases which degrade the insoluble chitin in to soluble chitooligosaccharides and glucosamine. Chitooligosaccharides possess antitumor, antifungal, antibacterial and immuno-enhancing effects. Antagonistic bacteria and chitinases have been exploited as potential biocontrol agents against fungal pathogens in plants. The growing number of application areas for chitin and chitin-derived products demand an equally diverse array of chitin-modifying enzymes for specific needs. The chapter will focus on the applications of chitinolytic enzymes from microbial sources and their possible applications, with special focus on conversion of large quantities of the chitinous substrates into useful biological products. © 2012 Springer Science+Business Media B.V. All rights reserved.
A comparative genomics and population genetics tool box consisting of parallelized versions of popular software programs is being put in place on the Paracel HPC at ICRISAT for all interested users. A number of software was configured to work on all four nodes (eight processors) of the HPC. All the tools are open-source, they include the sequence clustering tool ‘MegaBlast’, sequence assembly tool ‘PCAP’ with improvements over the original program, ‘Polybayes’ for SNP marker detection, ‘SNP2CAPS’ a tool to convert SNPmarkers to CAPS markers, and the software used in population genetics ‘Structure’. Parallelization of these tools allows for analysis of larger datasets with considerable reduction in time than would be possible with single processors. Web pages to the HPC and applications installed in it have also been written using PHP (language used for server side html embedded scripting) and PBSWEb (a web based interface to the portable batch system used for job scheduling, which uses PHP) accessible at
http://hpc.icrisat.cgiar.org/ and http://hpc.icrisat.cgiar.org/PBSWeb/
The study examine induction of defense enzymes involved in phenylpropanoid pathway and accumulation of pathogenesis related proteins in rot pathogen (Aspergillus niger Van Tieghem) challenged groundnut seedlings in response to Trichoderma viride JAU60. Seeds of five groundnut varieties differing in collar rot susceptibility were sown under non-infested, pathogen infested and pathogen + T. viride JAU60 seed treatment. Collar rot disease evident between 31.0% (J-11, GG-2) and 67.4% (GG-20) in different groundnut varieties under pathogen infested which was significantly reduced from 58.1% (J-11, GG-2) to 51.6% (GG-20) by Trichoderma treatment. The specific activities of polyphenol oxidase (EC 1.14.18.1) and β-1,3 glucanase (EC 3.2.1.6) elevated 3.5 and 2.3 fold, respectively, at 3 days; phenylalanine ammonia lyase (EC 4.3.1.5) evident 1.6 fold higher at 6 days; and chitinase (EC 3.2.1.14) sustained 2.3 to 2.8 folds up to 9 days in Trichoderma treated + pathogen infested seedlings of tolerant varieties (J-11, GG-2) compared with moderate and susceptible (GAUG-10, GG-13, GG-20). T. viride JAU60 induces defense enzymes in a different way for tolerant and susceptible varieties to combat the disease. This study indicates the synergism activation of defense enzymes under the pathogenic conditions or induced resistance by T. viride JAU60 in a different groundnut varieties susceptible to collar rot disease.
Copyright © 2015. Published by Elsevier B.V.
Bacterial biocontrol agents (BCAs) have been widely employed for minimizing the incidence and severity of several economically important crop diseases. Studies on the interactions between the bacterial BCAs and target microbial plant pathogens have revealed the involvement of different mechanisms of their biocontrol activities. Bacterial antagonism may be due to production of toxic metabolites (enzymes, antibiotics and volatile organic compounds), competition for nutrients and space, prevention of pathogen colonization of host tissues and induction of resistance in plants to crop diseases. The bacterial species included in the genera Pseudomonas, Bacillus, Burkholderia, Lysobacter, Serratia and Pantoea have been reported to be effective against several plant pathogens by acting through one or more mechanisms. The rhizobacterial species are potent biocontrol agents and also efficient promoters of plant growth, thus providing double benefits to the treated plants. Factors that influence the efficiency of the biocontrol agents have been studied. These studies are useful to select the suitable bacterial strain(s) that could provide higher level of protection to the plants under a particular set of environmental conditions existing in different agroecosystems.
This chapter deals with both naturally derived inducers (biotic inducers) of resistance and agents which mimic the action of these inducers (abiotic inducers). It concentrates on the effects of topical treatment with inducers on disease control under controlled conditions and in the field. Chitin is the main cell wall component of many filamentous fungi and, along with its deacetylated derivative chitosan, has been shown to elicit defence responses in plants, including lignification and phytoalexin production. Marine algae provide a source of numerous elicitors, including ulvans from green seaweeds, agarans and carrageenans from red seaweeds, and alginates, fucans and laminarin from brown seaweeds. The chapter provides an overview of the effects of Benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH) on a range of different host-pathogen interactions. The use of abiotic elicitors has become a major promising approach for the agricultural application of induced resistance.
Leaves of higher plants comprise perhaps the largest bacterial substrate on earth, yet we know very little about the bacteria that occupy these spaces. In this review, we first examine the ecology and behavior of bacteria that reside on leaf surfaces. Next, we discuss the ecological implications of foliar bacteria that reside in interior portions of leaf tissues. Later, we consider the studies on foliar bacteria in tropical habitats to date. Finally, we examine evidence regarding the potential roles of foliar bacteria in structuring tropical plant communities. Bacteria colonize the phyllosphere via animal vectors or passively from soil, wind, or rain, though there are too few data to determine the relative contributions of these sources to the phyllosphere. Additionally, the degree to which parent plants transmit bacteria to offspring via seed remains unknown. We predict that high temperature, high humidity, low UV radiation, and leaf architecture in the tropical understory enable tropical leaves to support more abundant and diverse bacterial communities compared to temperate leaves. While the extent of competitive interactions among bacteria remains poorly resolved, evidence from agricultural crop species and Arabidopsis thaliana suggests that these interactions cause niche partitioning based on carbon use. The degree to which phyllobacteria and endophytes of tropical plants are pathogenic versus mutualistic or neutral remains unexplored. We hypothesize, however, that the detrimental impact of bacterial pathogens ultimately increases as the abundance of single host tree species increases, which can promote and maintain plant diversity in tropical forests.
Chitin is a biodegradable polymer widely spread in nature. It is mainly obtained form crustacean shells. Chitin and its derivatives have shown to be effective in controlling plagues and plants diseases. Their mechanism of action is strongly linked to their chemical structures. These mechanisms can result from the direct action on the pathogen or can be a consequence of its capacity to induce defensive mechanisms on plants. In any case, the effect is their protection against various vegetable diseases, before and after harvest. The addition of chitin and its derivatives to the soil favours the growth and activity of many chitinolytic organisms that constitute biological controls and are natural enemies of many agents responsible for vegetable plagues and diseases, generating a synergistic effect. On the other side, these biopolymers also favour the growth and development of beneficial microorganisms that establish synergistic relationships with plants, such a as mycorrhizas or Rhizobium species. On top of that, increasing the microbial population and activity in the soil improves the properties of nutrients and their availability. As growth regulators, it has been established that these biopolymers accelerate seeds germination, the ability of plants to grow as well as the agricultural yield. It is concluded that chitin and its derivatives have great potential for applications in agriculture. It is foreseen that in the future these biopolymers will be used in greater extension, mainly for substituting actual chemical pesticides or as growth regulators.
Groundnut (Arachis hypogaea L.) is a major oilseed crop widely grown in tropical and subtropical regions of the world and is an important source of protein. Diseases pose a major threat to the production of groundnut each year, and prevention of disease in groundnut is a major concern for producers. Soil-borne diseases are especially complicated to manage due to the difficulty of dispersing fungicides through the groundnut canopy to the soil profile. Chemical control methods are ineffective and are not ecofriendly as they increase environmental and health hazards. Implementation of IDM (Integrated Disease Management) in developing countries is gaining momentum but still requires more serious efforts to achieve impact at the country or regional level. The success and sustainability of IDM strategy, especially with resource poor farmers, greatly depends on their involvement in helping generate locally specific techniques and solutions suitable for their particular farming systems and integrating control components that are ecologically sound and readily available to them. The biological control of soil-borne pathogens with antagonistic bacteria belonging to plant growth-promoting rhizobacteria like Pseudomonads, Bacillus, Rhizobium, etc., has received prominent attention because of the dual role of these bacteria in plant growth promotion and disease control. This chapter describes these developments and the variety of approaches that have been used to implement biological control as a useful tactic in IDM. It also describes how biological control interacts with other tactics and the potential for better integration into IDM programs.
Chitin is a biodegradable polymer widely spread in nature. It is mainly obtained form crustacean shells. Chitin and its derivatives have shown to be effective in controlling plagues and plants diseases. Their mechanism of action is strongly linked to their chemical structures. These mechanisms can result from the direct action on the pathogen or can be a consequence of its capacity to induce defensive mechanisms on plants. In any case, the effect is their protection against various vegetable diseases, before and after harvest. The addition of chitin and its derivatives to the soil favours the growth and activity of many chitinolytic organisms that constitute biological controls and are natural enemies of many agents responsible for vegetable plagues and diseases, generating a synergistic effect. On the other side, these biopolymers also favour the growth and development of beneficial microorganisms that establish synergistic relationships with plants, such a as mycorrhizas or Rhizobium species. On top of that, increasing the microbial population and activity in the soil improves the properties of nutrients and their availability. As growth regulators, it has been established that these biopolymers accelerate seeds germination, the ability of plants to grow as well as the agricultural yield. It is concluded that chitin and its derivatives have great potential for applications in agriculture. It is foreseen that in the future these biopolymers will be used in greater extension, mainly for substituting actual chemical pesticides or as growth regulators.
Pseudomonas aeruginosa GSE 18, reduced the pre-emergence rotting and post-emergence wilting of groundnut by >60% in A. niger-infested potting mixture. Bacterial seed treatment induced the rapid accumulation of defence-related enzymes like chitinase,
β-1,3-glucanase, peroxidase and phenylalanine ammonia lyase (PAL) in groundnut seedlings compared with the control. Activities
of these enzymes were significantly (P=0.01) higher in GSE 18-treated seedlings than the control, with activation of PAL being the highest (>2-fold). Cell-free
culture filtrate of P. aeruginosa GSE 18 inhibited the in vitro production of polygalacturonase and cellulase by A. niger up to 77% and 68%, respectively, 6 days after inoculation. Thus, activation of host defence responses and inhibition of fungal
cell wall-degrading enzymes appear to play a significant role in the biocontrol activity of GSE 18 in collar rot of groundnut.
IntroductionBiotic InducersAbiotic InducersConclusions
AcknowledgementsReferences
Plants respond to pathogen attack by the induction of a battery of defenses, suggesting that different protective mechanisms may have complementary roles in the overall expression of disease resistance. We have investigated possible functional interactions between two different hydrolytic enzymes, chitinase and glucanase, by constitutive co-expression in transgenic tobacco of genes encoding the rice RCH10 basic chitinase and the alfalfa AGLU1 acidic glucanase. Hybrid plants were generated by crossing transgenic parental lines exhibiting strong constitutive expression of cauliflower mosaic virus (CaMV) 35S enhancer / RCH10 and CaMV 35S double promoter / AGLU1 gene fusions, respectively. Evaluation of disease development in these hybrids, heterozygous for each transgene, and in homozygous selfed progeny, showed that combination of the two transgenes gave substantially greater protection against the fungal pathogen Cercospora nicotianae, causal agent of frogeye, than either transgene alone. Productive interactions between chitinase and glucanase transgenes in vivo point to combinatorial expression of antimicrobial genes as an effective approach to engineering enhanced crop protection against fungal disease.
Chitinase and β-1,3-glucanase purified from pea pods acted synergistically in the degradation of fungal cell walls. The antifungal potential of the two enzymes was studied directly by adding protein preparations to paper discs placed on agar plates containing germinated fungal spores. Protein extracts from pea pods infected with Fusarium solani f.sp. phaseoli, which contained high activities of chitinase and β-1,3-glucanase, inhibited growth of 15 out of 18 fungi tested. Protein extracts from uninfected pea pods, which contained low activities of chitinase and β-1,3-glucanase, did not inhibit fungal growth. Purified chitinase and β-1,3-glucanase, tested individually, did not inhibit growth of most of the test fungi. Only Trichoderma viride was inhibited by chitinase alone, and only Fusarium solani f.sp. pisi was inhibited by β-1,3-glucanase alone. However, combinations of purified chitinase and β-1,3-glucanase inhibited all fungi tested as effectively as crude protein extracts containing the same enzyme activities. The pea pathogen, Fusarium solani f.sp. pisi, and the nonpathogen of peas, Fusarium solani f.sp. phaseoli, were similarly strongly inhibited by chitinase and β-1,3-glucanase, indicating that the differential pathogenicity of the two fungi is not due to differential sensitivity to the pea enzymes. Inhibition of fungal growth was caused by the lysis of the hyphal tips.
Over 120 bacterial strains were evaluated in a greenhouse for control of bean rust caused by Uromyces appendiculatus. The strains, found previously to be antagonistic to some fungal pathogens, were isolated from dry edible bean (Phaseolus vulgaris) and other hosts. Only Pantoea agglomerans B1, from a bean blossom, and Stenotrophomonas maltophilia C3, a chitinolytic strain from a Kentucky bluegrass leaf, were effective in multiple experiments in reducing bean rust severity. The addition of colloidal chitin to C3 cell suspensions and treatment with chitin broth cultures of C3 were evaluated as methods to improve biocontrol efficacy of C3. While chitin amendments increased rust control in the greenhouse as compared to C3 cells in buffer, chitin broth cultures gave the highest- and longest-lasting level of control. In four field experiments, treatments with C3 suspended in buffer, with and without chitin amendment, reduced rust severity in only one experiment. Strain B1 was not effective. In three other field experiments, C3 chitin broth cultures were comparable to multiple applications of thiophanate methyl or thiophanate methyl combined with manganese ethylenebisdithiocarbamate (maneb) in reducing bean rust severity.
Arabidopsis ecotype Columbia (Col-0) seedlings, transformed with a phenylalanine ammonia-lyase 1 promoter (PAL1)-[beta]-glucuronidase (GUS) reporter construct, were inoculated with virulent and avirulent isolates of Peronospora parasitica. The PAL1 promoter was constitutively active in the light in vascular tissue but was induced only in the vicinity of fungal structures in the incompatible interaction. A double-staining procedure was developed to distinguish between GUS activity and fungal structures. The PAL1 promoter was activated in cells undergoing lignification in the incompatible interaction in response to the pathogen. Pretreatment of the seedlings with 2-aminoindan-2-phosphonic acid (AIP), a highly specific PAL inhibitor, made the plants completely susceptible. Lignification was suppressed after AIP treatment, and surprisingly, pathogen-induced PAL1 promoter activity could not be detected. Treatment of the seedlings with 2-hydroxyphenylaminosulphinyl acetic acid (1,1-dimethyl ester) (OH-PAS), a cinnamyl alcohol dehydrogenase inhibitor specific for the lignification pathway, also caused a shift toward susceptibility, but the effect was not as pronounced as it was with AIP. Significantly, although OH-PAS suppressed pathogen-induced lignification, it did not suppress pathogen-induced PAL1 promoter activation. Salicylic acid (SA), supplied to AIP-treated plants, restored resistance and both pathogen-induced lignification and activation of the PAL1 promoter. Endogenous SA levels increased significantly in the incompatible but not in the compatible combination, and this increase was suppressed by AIP but not by OH-PAS. These results provide evidence of the central role of SA in genetically determined plant disease resistance and show that lignification per se, although providing a component of the resistance mechanism, is not the deciding factor between resistance and susceptibility.
Elicitation of soybean cells causes a rapid insolubilization of two cell wall structural proteins, p33 and p100. Likewise, a short elicitation of 30 min rendered cell walls more refractory to enzyme digestion as assayed by the yield of protoplasts released. This effect could be ascribed to protein cross-linking because of its insensitivity to inhibitors of transcription (actinomycin D) and translation (cycloheximide) and its induction by exogenous H2O2. Moreover, the induced loss of protoplasts could be prevented by preincubation with DTT, which also blocks peroxidase-mediated oxidative cross-linking. The operation of protein insolubilization in plant defense was also demonstrated by its occurrence in the incompatible interaction but not in the compatible interaction between soybean and Pseudomonas syringae pv glycinea. Likewise, protein insolubilization was observed in bean during non-host hypersensitive resistance to the tobacco pathogen P. s. pv tabaci mediated by the hypersensitive resistance and pathogenicity (Hrp) gene cluster. Our data strongly suggest that rapid protein insolubilization leads to a strengthened cell wall, and this mechanism functions as a rapid defense in the initial stages of the hypersensitive response prior to deployment of transcription-dependent defenses.
Both phenylalanine ammonia lyase and tyrosine ammonia lyase were detected in tobacco (Nicotiana tabacum L. Wisconsin 38) callus. The enzymes were separated from each other by Sephadex G-200 column chromatography. Increased activity of tyrosine ammonia lyase was observed during culture of tobacco callus under shoot-forming conditions, while activity of phenylalanine ammonia lyase increased during culture under non-organ-forming conditions. Confirmation of these findings was obtained by examining the incorporation of [(14)C]tyrosine and [(14)C]phenylalanine into p-coumarate and trans-cinnamate, respectively.
Chitinase and beta-1,3-glucanase purified from pea pods acted synergistically in the degradation of fungal cell walls. The antifungal potential of the two enzymes was studied directly by adding protein preparations to paper discs placed on agar plates containing germinated fungal spores. Protein extracts from pea pods infected with Fusarium solani f.sp. phaseoli, which contained high activities of chitinase and beta-1,3-glucanase, inhibited growth of 15 out of 18 fungi tested. Protein extracts from uninfected pea pods, which contained low activities of chitinase and beta-1,3-glucanase, did not inhibit fungal growth. Purified chitinase and beta-1,3-glucanase, tested individually, did not inhibit growth of most of the test fungi. Only Trichoderma viride was inhibited by chitinase alone, and only Fusarium solani f.sp. pisi was inhibited by beta-1,3-glucanase alone. However, combinations of purified chitinase and beta-1,3-glucanase inhibited all fungi tested as effectively as crude protein extracts containing the same enzyme activities. The pea pathogen, Fusarium solani f.sp. pisi, and the nonpathogen of peas, Fusarium solani f.sp. phaseoli, were similarly strongly inhibited by chitinase and beta-1,3-glucanase, indicating that the differential pathogenicity of the two fungi is not due to differential sensitivity to the pea enzymes. Inhibition of fungal growth was caused by the lysis of the hyphal tips.
Foliar application of a plant growth-promoting rhizobacterium, Pseudomonas fluorescens strain Pf1 significantly controlled late leaf spot and rust diseases of groundnut (Arachis hypogaea L.) under greenhouse conditions. Groundnut plants, when sprayed with P. fluorescensstrain Pf1, showed increase in activity of phenylalanine ammonia-lyase 1 day after application and the maximum enzyme activity was detected at 3 days after treatment. An increase in phenolic content was observed 1 day after P. fluorescens treatment. Also chitinase and β-1,3-glucanase activities increased significantly 1 day after P. fluorescens treatment and maximum activities were reached 4 days later. Application of P. fluorescens to groundnut leaves induced accumulation of a 23-kDa thaumatin-like protein (TLP) and a 30-kDa glucanase. The induction of 23-kDa TLP was detected only in treated leaves and not in roots, stems and petioles of the groundnut plants. The 30-kDa glucanase started to accumulate 1 day after treatment and the level of the protein continued to increase throughout the experimental period of 4 days. Both TLP and glucanase were found in the intercellular fluid of P. fluorescens-sprayed groundnut leaves.
Chitin applied as an amendment to peanut leaves increased the populations of indigenous chitinolytic epiphytes from <1% to >40% of the total microflora. The total epiphytic bacterial populations increased by up to 0.3 log with the addition of chitin. When the chitinolytic Bacillus cereus strain 304 isolated from chitin-amended leaves was reapplied to peanut foliage with chitin, its populations were sustained as actively growing vegetative cells for a longer period than when applied to nonamended leaves. Eight days after application, B. cereus populations were > 1 log higher on chitin-amended leaves than on nonamended leaves. In two of three field trials, significant reductions in the severity of early leafspot caused by Cercospora arachidicola were seen on chitin-amended leaves, and a trend toward additional control (P < 0.10) was obtained on leaves treated with chitin plus the chitinolytic B. cereus. Scanning electron microscopy revealed chitin deposits, fungal hyphae, and spores colonized by bacilliform bacteria. Colonized fungal hyphae and spores were pitted and distorted, indicating a potential for biological control of chitin-containing fungal pathogens by chitinolytic bacterial antagonists.
Induction of phytoalexin formation in suspension-cultured rice cells by a series of N-acetylchitooligosaccharides and chitooligosaccharides was studied. N-acetylchitooligosaccharides larger than hexaose induced the formation of momilactones A and B as well as oryzalexins A, B, and D at very low concentrations like 10− 9–10− 6 M (N-acetylchitoheptaose). GlcNAc oligomers smaller than trimers had almost no activity and a series of deacetylated chitooligosaccharides were also inactive. Strict requirement for the size and structure of GlcNAc oligomers as well as the sensitivity to them strongly indicates the presence of recognition systems specific for these compounds in rice cells. The level of momilactone A produced reached 100–500 μg/g of cultured cells, which appeared to be enough to prevent the growth of pathogenic fungi such as Pyricularia oryzae, thus indicating the importance of this phenomenon in the defense systems of rice plants. Suspension-cultured cells obtained only from a suitable period of cultivation, mainly those from lag phase, could respond to the elicitor and produce phytoalexins.
SUMMARYA variable dew-point chamber which simulates dew fall on plant parts within a temperature range of 1–35° C is described, with technical data on construction and performance. Although designed to obtain uniform infections of cereal leaves following their inoculation with rust uredospores in a settling tower, possible wider uses of the apparatus in biological research are discussed.
Roles for oligosaccharides as signals for activating defensive and developmental processes have continued to be reported and supported in the recent literature. Studies of recognation events employing defined oligosaccharides indicate that oligosaccharides interact with cellular membrane receptors in a hormone-like manner to affect gene regulation. Recent studies concerning the regulation of signal production (e.g. studies of the roles PGIPAs play in regulating the effective half-lives of oligouronides in infected tissues; and investigations of possible roles for cell wall fragments in morphogenesis, hypersensitivity, fruit ripening, and cell elongation) provide further evidence that oligosaccharides signal developmental responses. In plants, as in animals, our understanding of how complex carbohydrates may function in signaling and recognition systems is still in its infancy.
Plants constitute the largest and most important group of autotrophic life-forms on earth. Their abundant organic material serves as a nutritional source for all heterotrophic organisms, including animals, insects, and microbes. This chapter discusses pathogen ingress and plant resistance, classes of plant defense responses, regulation of defense gene expression, and defense responses and resistance. Plant pathogens usually express several virulence functions that increase their ability to colonize and damage host plants. Enormous progress has been made over the past decades in the understanding of the highly complex molecular events that occur in plant-pathogen interactions. A large body of circumstantial evidence has accumulated, implicating diverse biochemical responses in plant defense. Despite species-specific differences, plants do appear to have evolved common basic defense strategies comprising very rapid, localized, and systemic defense mechanisms for establishing resistance. Although the knowledge is still rudimentary, a number of common signaling molecules have been identified lending insight to the signal transduction pathways employed for intra- and intercellular communication. Manipulation of biosynthetic pathways involving multiple genes, such as the biosynthesis of phytoalexins, has not yet been achieved, although it should be feasible to modify rate-limiting steps of pathways or to divert precursors into novel pathways by the introduction of defined genes.
Peroxidase, IAA oxidase and polyphenol oxidase activities were detected in tobacco cells in suspension culture. Using gel filtration, ion-exchange chromatography and disc gel electrophoresis, it was concluded that IAA oxidase activity is entirely due to peroxidases. Peroxidase and polyphenol oxidase zymograms using anionic gel separation were also similar, but the occurrence of true polyphenol oxidases, distinct from peroxidase, was demonstrated by cationic disc gel electrophoresis and gel filtration.
Metabolic products of polyunsaturated fatty acids have been variously implicated in control of microbial pathogens. Induced resistance has been shown as one of the mechanisms of biological control by plant growth promoting rhizobacteria (PGPR). This paper reports a significant lipoxygenase (LOX) activity in groundnut seedlings with production of 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-hydroperoxyoctadecatrienoic acid (13-HPOTrE) as major products with linoleic acid (LA) and -linolenic acid (ALA), respectively. Both the hydroperoxides are inhibitory to the growth of Aspergillus niger as measured in micro titer plates. Ours is the first report on induction of LOX activities in groundnut on treatment with a PGPR strain Bacillus subtilis AF 1, and with crown-rot pathogen, A. niger. Treatment with B. subtilis AF 1 enhanced LOX levels in groundnut similarly but earlier to A. niger – treatment. This induction of LOX during activation of growth and pathogen infection was discussed in light of the reported involvement of LOX both in growth and development as well as in plant-pathogen interaction, particularly induced disease resistance.
Two rice cDNAs, EL5 and RRF1, were isolated and characterized. EL5 was responsive to N-acetylchitooligosaccharide, a biotic elicitor active in suspension-cultured rice cells. The structural specificity of the elicitor required for the expression of EL5 was consistent with other defense reactions observed in the experimental system, indicating that the elicitor signal to EL5 is transmitted through a single class of receptor-mediated recognition events. However, the intracellular signaling pathway to EL5 was distinct from those to other elicitor-responsive genes. Sequence analysis and alignment showed that a genomic sequence stored in rice genome databases in addition to EL5 and RRF1 belongs to the ATL family of RING-H2 finger motif proteins first isolated from Arabidopsis.
Chitosan (1000 ppm) reduced germination of uredospores of Puccinia arachidis, the incitant of groundnut leaf rust disease. Chitosan treatment of groundnut leaves before inoculation reduced the number of lesions, lesion diameter and sporulation of P. arachidis. Chitosan-treated leaves showed an increase in endogenous salicylic acid, intercellular chitinase and glucanase activity. These compounds had been previously associated with induced resistance responses. Enzyme activity staining showed new isoforms of chitinase and glucanase in treated groundnut leaves. Western blot analysis of treated groundnut leaves also showed new isoforms of chitinase and glucanase.
Stem injection of tobacco plants with sporangiospores of Peronospora tabacina or inoculating three to four lower leaves with tobacco mosaic virus (TMV) systemically protected plants against blue mould caused by P. tabacina and systemically increased total β-1,3-glucanase activity. The onset and level of systemic protection was correlated with the elevation of the total enzyme activity in the systemically protected leaves. The total enzyme activity was higher in the protected plants than in the controls at the time of challenge with P. tabacina and during the first 1−4 days after challenge. Direct detection of β-1,3-glucanases after native 15% polyacrylamide gel electrophoresis (PAGE) run with an anodic buffer system revealed the presence of four major isoforms, designated G1, G2, G3 and G4, in the challenged tobacco leaves. The activities of G1 and G2 were higher in leaves of systemically protected plants than in those of the controls during early stages after challenge. G3 was not associated with protection. Its activity in the protected plants did not change before or after challenge. A similar activity was present in the control plants before challenge and at early stage after challenge, but the activity decreased in the control after the appearance of symptoms. The same three isoforms, based on electrophoretic mobilities, were obtained from Ky 14 plants induced by leaf inoculation with TMV or by stem injection with P. tabacina or from Samsun NN plants induced by leaf inoculation with TMV. G4 appeared at the time of symptom expression in control plants, and it appeared to be produced by P. tabacina. Experiments with protoplasts and intercellular fluid indicated that G1, G2 and G3 were predominantly located in intercellular spaces and G3 appeared bound more tightly to cell walls than G1 and G2. These β-1,3-glucanase isoforms were compared on PAGE gels with the four β-1,3-glucanases and 10 PR-proteins previously reported in tobacco. G1 co-migrated with PR-N (2b); G2 co-migrated with PR-O (2c); G3 did not co-migrate with any of the 10 PR-proteins or four β-1,3-glucanases reported previously. Increasing the amount of total protein of crude enzyme extract applied to 15% PAGE gels from 200 μg to 400 μg per lane revealed two more β-1,3-glucanase bands, one co-migrated with PR-2 (2a) and another (designated as G5) that did not co-migrate with any of the 10 PR-proteins or four β-1,3-glucanases previously reported in tobacco. These isoforms were more easily detected on 10% PAGE gels. G5 and PR-2 (2a) were also systemically induced in the TMV-induced plants.
Biological control in the leaf-surface habitat is examined with emphasis on plant-microbe interactions, viz microbial antagonism by epiphytes or endophytes. Microbe-directed tactics to enhance efficacy can be divided into those designed to promote colonization (by an otherwise effective antagonist) and those aiming to increase antagonistic potency (of a good colonist). -P.J.Jarvis
We investigated whether a plant chitinase can be used as a biocontrol agent instead of chemical fungicides by spraying chitinase E (family 19; class IV) from a yam (Dioscorea opposita Thunb) alone or together with beta-1,3-glucanase directly onto the surface of a powdery mildew infecting strawberry berries and leaves. Results were observed by eye and with a scanning electron microscope. The powdery mildew infecting the strawberries was degraded, mainly by the chitinase, and the disease did not appear again for more than 2 weeks. These results indicated that this kind of plant chitinase might be safe and biodegradable biocontrol agent for use instead of conventional fungicides.
In foliar and postharvest biocontrol systems, the use of active metabolites produced by antagonistic microorganisms is advantageous compared with the use of living microorganisms. Chitinases, a major group of hydrolytic enzymes produced by biocontrol agents, are involved in the lysis of cell walls of pathogenic fungi. In the present study, an attempt was made to test the partially purified beta-1,4-N-acetylglucosaminidase (NAGase) of a biocontrol strain Bacillus subtilis AF 1 for control of rust in groundnut (caused by Puccinia arachidis) and soft rot in lemons (caused by Aspergillus niger). Four proteins of molecular mass 67, 40, 37, and 32 kDa were isolated from the culture filtrates of AF 1 by affinity chromatography, of which the 67-kDa protein has detectable chitinolytic ability. This protein (NAGase) effectively inhibited the in vitro growth of A. niger in microtitre plates. In the presence of NAGase, germination of urediniospores of P. arachidis was reduced by 96% compared with the control. In a detached leaf bioassay, NAGase reduced the rust lesion frequency by >60%. NAGase significantly reduced the incidence of soft rot in harvested lemon fruits. However, fresh cells and (or) alginate formulation of AF 1 were more effective than NAGase in control of both of the test plant - pathogen systems.
Bacteria associated with 6 habitats of groundnut were evaluated for their broad-spectrum antifungal activity and suppression of collar rot (Aspergillus niger) of groundnut. Three hundred and ninety-three strains were tested against 8 fungal pathogens of groundnut including 5 necrotrophic fungi, Aspergillus flavus, A. niger, Rhizoctonia bataticola, Rhizoctonia solani, and Sclerotium rolfsii, and 3 biotrophic fungi, Cercospora arachidicola, Phaeoisariopsis personata, and Puccinia arachidis. Pseudomonas sp. GRS 175, Pseudomonas aeruginosa GPS 21, GSE 18, GSE 19, and GSE 30, and their cell-free culture filtrates were highly antagonistic to all the test fungi. The cell-free culture filtrates of these bacteria were fungicidal and induced mycelial deformations including hyphal bulging and vacuolization in necrotrophic fungi. The cell-free culture filtrates at 10% (v/v) concentration significantly inhibited the spore germination of biotrophic fungi. In the greenhouse, P. aeruginosa GSE 18 emerged as an effective biocontrol agent of collar rot closely followed by P. aeruginosa GSE 19. The bacterium applied as a seed treatment reduced the pre-emergence rotting and postemergence wilting by > 60%. Pseudomonas aeruginosa GSE 18 effectively colonized the groundnut rhizosphere, both in native and in A. niger infested potting mixtures. Ninety-day-old peat formulation of P. aeruginosa GSE 18 had biocontrol ability comparable with the midlog-phase cells. Pseudomonas aeruginosa GSE 18, tolerant to thiram, in combination with the fungicide had an improved collar rot control. The present study was a successful attempt in selection of broad-spectrum and fungicide tolerant biocontrol agents that can be a useful component of integrated management of collar rot.
Evaluation of chitinolyt-ic strains of Serratia marcescens and Bacillus circulans for biologi-cal control of late leaf spot of groundnut
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Evaluation of chitinolytic strains of and for biological control of late leaf spot of groundnut . In: held on 28-30
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- A R Rao
- Podile
Evaluation of chitinolytic strains of Serratia marcescens and Bacillus circulans for biological control of late leaf spot of groundnut
- Kishore GK