Characterization and Identification of Native Pseudomonads from Red and Lateritic Regions of West Bengal

Abstract

Agricultural crops are facing a continuous threat due to biotic and abiotic stresses, thus, limiting the crop productivity, and thereby, threatening food security. Plant roots attract several kinds of microbes that induce resistance in plants against these stresses by enhancing the activity of the antioxidant enzymes, phenolic and other non-phenolic compounds, and thereby, have a beneficial effect on plants. Vast research has been carried out on biocontrol agents to manage soil-borne plant pathogens, but there has been limited success in the development of region-specific, commercially viable microbial inoculants. The present research was framed with a view to screen and evaluate native Pseudomonads from the rhizosphere of different crops in lateritic soils and their exploitation in biotic and abiotic stress management under the red and lateritic zone of West Bengal. In the lateritic area of West Bengal, the lowest pH as well as the highest culturable rhizobacterial population was found in the soil of Bankura. Among all the isolated rhizobacteria, 43.33% were found to be moderately antagonistic against three different soil-borne plant pathogens viz., Rhizoctonia solani, Sclerotinia sclerotiorum and Sclerotium rolfsii—while only 6.67% were found to be very highly antagonistic against these soil-borne plant pathogens. Augmented seeds of tomato, cowpea and French bean with native rhizobacteria enhanced the vigour index and 16.67% of the isolates were found to have a high value of vigour index in the normal and acid stress conditions. Based on acid tolerance, antagonistic activity and the seed vigour assay, a total of 13 isolates from 97 of lateritic area were selected. Out of the 13 selected isolates, 7 were positive for protease and lipase production, 8 isolates were positive for the production of HCN, siderophore and salicylic acid production and 9 isolates were found to be positive for IAA, phosphate solubilisation, amylase and chitinase production. Species of beneficial Pseudomonads such as Pseudomonas aeruginosa, P. fluorescens, P. Plecoglossicida, P. helmanticensis, P. geniculate, P. baetica and P. putida were found. Five isolates were used to study the effect on plant growth in terms of germination (%), root and shoot length, as well as fresh root and shoot weight and disease patterns in terms of pre- and post-emergence damping-off under the semi-field condition.