Biocontrol ability of indigenous <i>Pseudomonas</i> sp.VSMKU4040 against economically important fungal phytopathogens for the sustainable agriculture

Crop activation relies completely on the rhizosphere’s bacteria. In this instance, we looked into the effectiveness of Pseudomonas spp. present in the root zone of tomato against various plant diseases like Rhizoctonia solani, Sclerotium rolfsii, and Fusarium oxysporum RACE, which range from 12.33mm to 21.66mm in the Zone of Inhibition (ZOI). Interestingly, all five Pseudomonas spp. significantly produced antimicrobial and plant growth-promoting traits involved in plant development, including siderophore, hydrogen cyanide, IAA, and phosphate solubilization. Furthermore, the biocontrol mechanism of parasitism was found to be considerably influenced by the secretion of hydrolytic enzymes by Pseudomonas spp., including chitinase, cellulase, protease, and amylase. The particular strain designated as VSMKU4040 was selected for further study out of five strains of Pseudomonas spp. because of its outstanding antagonism and other unique biological control mechanism properties. The cell-free culture supernatant of Pseudomonas spp. effectively suppressed almost all of the fungal plant diseases indicated above, compared to the control. Pinch of R. solani and S. rolfsii mycelia from the ZOI during interaction with a Pseudomonas spp. VSMKU4040 was processed for examination under a scanning electron microscope. In comparison to the control, we discover that R. solani mycelium broke, disintegrated, and deformed. In contrast, during Pseudomonas spp. VSMKU4040 interaction with S. rolfsii, there was no initiation of sclerotia development along with Pseudomonas spp. VSMKU4040 distribution, whereas in the control, we could observe the formation and intimation of sclerotia bodies in S. rolfsii, in comparison to the control. When the 16s rRNA encoding gene was compared to a 1kb marker, 1500 bp was found in Pseudomonas spp. VSMKU4040. The pure ethyl acetate extract yielded three distinct metabolites, each with a different Rf value (0.91, 0.85, and 0.8) that were found in Thin-Layer Chromatography (TLC). By using the good diffusion method, the second molecule (0.85) out of the three showed significant potential activity against fungal plant pathogens at 30μg/ml when compared to a commercial fungicide companion.