Rhizospheric Pseudomonas spp. with plant growth promotion and antifungal properties against Sclerotium rolfsii mediated pathogenesis in Vigna unguiculata

The plant beneficial mechanisms shown by rhizobacteria are remarkable in its nature, distribution and execution. In the study, 11 rhizospheric bacterial isolates of Cyclea peltata (Indian moon-seed) were found to have strong inhibitory activity against Pythium myriotylum and Rhizoctonia solani. Among these, two Pseudomonas spp. (K6 and DN18) were identified to have a differential distribution of antifungal mechanisms. By LC–MS analysis, K6 and DN18 have been confirmed for the presence of metabolites such as phenazine-1-carboxylic acid (PCA), mono-rhamnolipid and di-rhamnolipid, 1-hydroxy phenazine, pyocyanin and pyrrolnitrin. Due to the well-demonstrated antifungal mechanisms of these compounds, the natural logic behind its rhizospheric presence can primarily be plant protective. A further molecular investigation has resulted in the identification of the gene responsible for rhamnolipid biosynthesis in Pseudomonas spp. K6 and DN18. In addition, isolate K6 has been confirmed for the production of chitinase in colloidal chitin agar. The wide range of chemical and enzymatic antifungal mechanisms shown by the isolated Pseudomonas spp. have also been found to offer growth enhancement and suppression of disease caused by Sclerotium rolfsii in cowpea (Vigna unguiculata (L.) Walp.) plants which make the study significant. Because of the enormous potential to control phytopathogens and augment plant growth, these candidate organisms can have field application potential.