Evaluation of fluorescent pseudomonads for the management of sheath blight and bacterial blight of rice

Abstract

Biological control of major foliar diseases of rice in Kerala viz., sheath blight and bacterial blight using fluorescent pseudomonads was studied. Isolates obtained from the phylloplane were observed to be effective In inhibiting the growth of foliar pathogens. Isolate P 11 was most effective In inhibiting the growth of Rhizoctonia solani inciting sheath blight disease whereas growth of bacterial blight pathogen Xanthomonas oryzae pv oryzae . was suppressed by the isolate P33, under in vitro conditions. P 11 and P33 survived well in the inert material talc used as carrier material in the formulation developed, using these isolates. Seed treatment with talc based formulation of each isolate (P 11 and P33) increased the dry weight of root and shoot of rice seedlings of cultivar Jyothi and TN-l 14 days after sowing. The isolates produced almost equal and detectable amounts of IAA in culture supernatant. Greenhouse studies conducted at the College of Agriculture, Vellayani, indicated that a combination of seed treatment (10g kg" seed), seedling root dipping (1 per cent solution), and foliar spray (1 per cent) with the formulation of PI 1 and P33 effectively suppressed sheath blight and bacterial blight disease respectively and also appreciably increased the biomass yield of treated rice plants. Three foliar sprays starting two days prior to inoculation with the pathogen, during the tillering stage of the crop enhanced the efficacy of seedling root dipping with the biocontrol formulation. Isolates P 11 and P33 were tentatively identified as Pseudomonas aeruginosa and Pseudomonas fluorescens biovar 1 respectively.