Evaluation of Pseudomonas sp. VSMKU-4046 for Suppression of Sheath Blight (ShB) of Rice in Detached Leaf Assay

Abstract

The study of root-associated bacteria and their antagonistic potential is important not only for understanding their ecological role in the rhizosphere and the interaction with plants but also for the suppression of soilborne plant pathogens. In this context, a total of 206 fluorescent pseudomonads (FPs) were isolated from rice rhizosphere from southern part of Tamil Nadu. Initially 113 isolates were found which were active against Rhizoctonia solani, of which 89 were strongly active against R. solani with zone of inhibition range from 10 to 32 mm. Production of lytic enzymes such as chitinase, cellulase, protease, amylase and pectinase was reported along with other characteristics including phosphate solubilisation and siderophore formation in 89 antagonistic fluorescent pseudomonads. Antagonistic fluorescent pseudomonads were also tested towards other fungal pathogens such as Macrophomina phaseolina, Fusarium oxysporum,Fusarium udum and Alternaria alternata. Among 89 the strain VSMKU-4046 has high antagonistic potential against R. solani. Strain VSMKU-4046 significantly controls sheath blight of rice compared to control using sclerotia of R. solani through detached leaf assay. The lesion length around the sclerotium was measured, and ShB severity was rated by the relative lesion height (RLH) method with the following formula:% RLH = 100 x Total height of lesions / Total leaf height. %RLH=100×totalheightoflesions/totalleafheight%RLH=100×totalheightoflesions/totalleafheight\%\text{RLH}=100\times\text{total}\text{height}\text{of}\text{lesions}/\text{total}\text{leaf}\text{height}