Efficacy of Thiram Seed Coating Concentrations and Pre-soaking Duration on Seedborne Fungal Pathogen, Curvularia sp. and Seed Vigor of Rice

Abstract

Fungicide coated seeds are beneficial against seed or soil borne pathogens in the very initial stage to minimize the indiscriminate use of chemicals for disease control in paddy fields. The present study investigated the effectiveness of three levels of thiram fungicide coated-seeds having different pre-soaking duration on inhibition of rice seed-borne fungal pathogen Curvularia sp. and the seed vigor. Treated paddy seeds (Var. Bg-300) in four concentrations of 0 (control), 0.5,1 and 1.5 g fungicide per kg seeds and four pre-soaking times of 5 minutes, 1, 2 and 3 days were used. Modified disk diffusion bioassay for seeds and agar well diffusion inhibition bioassay for seed soaked water (extracts) were performed using spread plates of Curvularia sp. Three days pre-soaked seeds were germinated in sterilized soil medium inoculated with Curvularia sp. to screen the plant vigor. The fungicidal activity of seeds was significantly higher in 1 and 1.5 g kg*1 fungicide treatments (p<0.05). At a given pre-soak duration, a significantly high inhibition was observed in the soaked water of seeds treated with 1 and 1.5 g kg*1 than 0.5 g kg_1of fungicide (p<0.05). The average root height of the seeds treated with 1.5 g kg*1 fungicide concentration was significantly higher (p<0.05) than the other treatments. However, no significant difference was observed for the shoot lengths among treatments. Thus it can be concluded that 1.5 g kg*1 thiram treatment is effective in inhibiting Curvularia sp. and improving seed vigor of Bg-300.