Fungal diseases result in significant losses of fruits and vegetables during handling, transportation and storage. At present, post-production fungal spoilage is predominantly controlled by using synthetic fungicides. Under the global climate change scenario and with the need for sustainable agriculture, biological control methods of fungal diseases, using antagonistic microorganisms, are emerging as ecofriendly alternatives to the use of fungicides. The potential of microbial antagonists, isolated from a diversity of natural habitats, for postharvest disease suppression has been investigated. Postharvest biocontrol systems involve tripartite interaction between microbial antagonists, the pathogen and the host, affected by environmental conditions. Several modes for fungistatic activities of microbial antagonists have been suggested, including competition for nutrients and space, mycoparasitism, secretion of antifungal antibiotics and volatile metabolites and induction of host resistance. Postharvest application of microbial antagonists is more successful for efficient disease control in comparison to pre-harvest application. Attempts have also been made to improve the overall efficacy of antagonists by combining them with different physical and chemical substances and methods. Globally, many microbe-based biocontrol products have been developed and registered for commercial use. The present review provides a brief overview on the use of microbial antagonists as postharvest biocontrol agents and summarises information on their isolation, mechanisms of action, application methods, efficacy enhancement, product formulation and commercialisation.
The present study aimed to identify, characterize, and evaluate native chitinolytic rhizobacteria as biocontrol potential against pigeon pea wilt disease, caused by Fusarium udum. A total of 53 isolated rhizobacteria was evaluated for their chitinolytic potential and possession of different antifungal traits. From the successive in vitro experiments and in vivo bioassay, 2 promising bacterial strains (NS-1 and NS-22) that exhibited strong chitinolytic activities and mycolytic action were biochemically characterized and identified as Pseudomonas spp. NS-1 (NCBI GenBank accession number-KT175909) and Bacillus spp. NS-22 (NCBI GenBank accession number-MH425454), using 16S rDNA sequencing. In planta, disease severities for Pseudomonas spp. NS-1-and Bacillus spp. NS-22-treated plants were only about 14.62 and 23.08%, respectively, as compared to pathogen-only control (67.34%) at the end of 4 weeks. Additionally, these bacteria improved plant germination and fresh and dry plant biomasses under pathogenchallenged conditions. Further, both the strains were able to cause a considerable amount of reduction in the fungal biomass, as revealed by bacteria-pathogen interaction studies in liquid culture. Scanning electron microscopy studies also revealed the strong antifungal activities of these 2 chitinolytic bacteria on the pathogen hyphae and mycelia. The curling, bulging, breakdown, and other dysfunctionalities in fungal hyphae were induced by the biocontrol bacteria. In nutshell, the present exclusive investigation demonstrated mycolytic potential and biocontrol prospects of the 2 promising bacteria (Pseudomonas spp. NS-1 and Bacillus spp. NS-22) for the sustainable Fusarium wilt management and as a phytostimulator in pigeon pea.
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