Urja Pandya

Role of allelochemicals in plant growth promoting rhizobacteria for biocontrol of phytopathogens

Soil borne fungal diseases pose serious constraints on agro-productivity. Biological control is non-hazardous strategy to control plant pathogens and improve crop productivity. PGPR (plant growth promoting rhizobacteria) have long been used as plant disease control agents. PGPR produced a wide range of secondary compounds that may act as signals--that is, allelochemicals that include metabolites, siderophores, antibiotics, volatile metabolites, enzymes and others. Their mode of action and molecular mechanisms provide a great awareness for their application for crop disease management. The present review highlights the role of PGPR strains, specifically referring to allelochemicals produced and molecular mechanisms. Further research to fine tune combinations of allelochemicals, plant-microbe-pathogen interaction will ultimately lead to better disease control.

Isolation and identification of allelochemicals produced by B. sonorensis for suppression of charcoal rot of Arachis hypogaea L.

Bacillus sonorensis MBCU2 isolated from vermicompost‐amended soil from Gujarat, India showed most antagonistic activity against Macrophomina phaseolina by dual culture screening. The culture supernatant of MBCU2 completely suppressed the mycelia growth of pathogen, indicating that suppression was due to the presence of allelochemicals in the culture filtrate. Results of scanning electron microscopy revealed that MBCU2 caused morphological alteration in mycelia of M. phaseolina as evident by hyphal lysis and perforation. Lipopeptides (iturin A and surfactin) produced by MBCU2 were detected and identified by MALDI‐TOF‐MS as well as liquid chromatography coupled with ESI‐MS/MS. Pot trial studies conducted by seed bacterization with MBCU2 resulted in statistically significant increase in Arachis hypogaea L. vegetative growth parameters such as root length (91%), shoot length (252%), fresh weight (71%), dry weight (57%), number of pod (128%), and number of seed (290%) in M. phaseolina infested soil over control as well as decreased M. phaseolina disease severity. We suggest that allelochemicals production can be linked to the mechanism of protection of A. hypogaea L. from M. phaseolina by B. sonorensis MBCU2.

Assessment of ecological diversity of rhizobacterial communities in vermicompost and analysis of their potential to improve plant growth

Present study was designed to determine the microbial diversity from three distinctive sites (amended with vermicompost) of Gujarat, India. A set of 76 strains were screened from total of 438 strains that exhibit plant growthpromoting (PGP) and antagonistic potential isolated from sites PS1 (Mehsana district), BS2 (Dantiwada district) and VS3 (Gandhinagar district). Their diversity indices were studied for determining the species richness and evenness of screened isolates. Results revealed that site BS2 showed the most significant diversity indices in terms of Shannon (H′ 1.525) and Simpson (1/D 5.120) than other two samples. Principal component analysis showed that bacterial diversity (H′) was correlated with the soil characteristics. Chickpea and groundnut plants inoculated with MBCU1 and MBCU3 isolates showed an increase in the vegetative growth parameters that evaluate plant growth when compared to uninoculated controls. Strains MBCU1 and MBCU3 were identified as Pseudomonas stutzeri and Pseudomonas mosselii, respectively, according to sequence analysis of the 16S rRNA gene. These both isolates belong to site BS2 and they showed specific PGP traits suggesting that these isolates can promote plant growth by more than one mechanism with respect to their higher diversity index.

Intensification of Aerobic Processing of the Organic Wastes into Compost

The review is devoted to modern achievement in area of the aerobic processing of the organic wastes in compost for improvement of an ecological condition of the environment and purposeful use at intensification of an agriculture. The methods of reception and characteristic of products of microbiological transformation household, agricultural and industrial wastes are considered.

Purification and characterization of antifungal chitinase from Bacillus safensis MBCU6 and its application for production of chito-oligosaccharides

Abstract The chitinase producing bacterial strain was isolated from the vermicompost amended site of Mehsana district of Gujarat, India, and identified as Bacillus safensis MBCU6 using 16S rDNA sequencing. The chitinase was purified by ammonium sulfate precipitation followed by diethylaminoethanol sepharose CL-6B column chromatography. The purified enzyme could be demonstrated as a single band on sodium dodecyl sulfate polyacryalamide gel electrophoresis analysis as well as clear zone on zymogram, with estimated molecular mass of 58 kDa. The optimum pH and temperature of chitinase were pH 7.0 and 60◦C, respectively. The purified chitinase exhibited high degree of antifungal activity particularly against pathogenic Macrophomina phaseolina (60%) and Rhizoctonia solani (73%) by dissolving their cell wall components. The purified enzyme could hydrolyze colloidal chitin to its oligomers. It infers that the chitinase produced by Bacillus safensis may play a significant role in the activity as a biopesticide and bioactive material production.

Integrated Diseases Management in Groundnut for Sustainable Productivity

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.

In Vitro Evaluation of PGPR Strains for Their Biocontrol Potential Against Fungal Pathogens

Crop protection has become a basic requirement of the sustainable agriculture to ensure increased crop production. Biological control has been actively practiced as a crop protection measure for more than five decades and the history of biocontrol, its successes and failures, have been extensively reviewed. Plant growth promoting rhizobacteria (PGPR) are an important group of microorganisms, which play a major role in the biocontrol of plant pathogens. All plant-associated microenvironments, especially the rhizosphere, are colonized in high abundances by antagonistic microbes. Between 1 and 35 % of the microbial inhabitants show antagonistic capacity to inhibit the growth of pathogens in vitro by various biocontrol mechanisms that include production of antibiotics, siderophores, lytic enzymes, HCN and induced systemic resistance. In recent years, the popularity of biocontrol agents has increased substantially, as extensive and systematic research has enhanced their effectiveness and consistency.

Multifarious allelochemicals exhibiting antifungal activity from Bacillus subtilis MBCU5

A potential antagonist, designated strain Bacillus subtilis MBCU5 was previously isolated from vermicompost-amended soils of Gandhinagar, Gujarat, India. Crude allelochemicals from strain MBCU5 displayed strong antifungal activity against Macrophomina phaseolina as well as Rhizoctonia solani. These crude allelochemicals were tentatively identified as iturin, fengycin and surfactin through TLC and HPTLC analysis. Lipopeptides produced by MBCU5 were identified by MALDI-TOF–MS and LC–ESI–MS/MS analysis showed that iturin homologues (m/z 1020–1120), surfactin (m/z 1008.7 and m/z 1022.7), fengycin A and fengycin B (m/z 1400–1550) types of allelochemicals which are responsible for antifungal activity against pathogens. PCR analysis showed presence of genes (i.e. Iturin A synthetase KJ531680 and Surfactin synthetase KJ601726) involved in the biosynthesis of allelochemicals. Many reports showed lipopeptides from Bacillus species; this is the first report executed of multifarious allelochemicals from vermicompost-amended soil due to the presence of predominant Bacillus species.