Determination of yield losses against sheath rot caused by Sarocladium oryzae in rice varieties with differential resistance

Abstract

Abstract Sheath rot (Sarocladium oryzae) of rice causes significant grain yield losses, warranting integrated, cost effective and eco-friendly management. With limited availability of highly resistant varieties, combining resistant / moderately resistant varieties with judicious and need based application of fungicides is a practical alternative. However, scarce information is available on the extent of yield losses in varieties with varied levels of resistance. This study evaluated yield losses in terms of 1000 grain weight (TGW) in rice varieties with varying resistance levels to sheath rot under protected conditions using fungicide azoxystrobin (11%) + tebuconazole (13.8%). It was observed that the differences in disease severity, AUDPC values and TGW loss were mainly attributed to the interaction effects among the treatment i.e. fungicide sprayed (protected) and fungicide non-sprayed (unprotected) treatment, and varieties & between varieties and years (P < 0.001). Plots with fungicidal application had a mean disease severity of 5.60% compared to 25.46% in untreated plots. Protected plots had a mean TGW of 24.80 g compared with 20.59 g in unprotected plots, reflecting a significant differences . Fungicide applications resulted in reduction of mean disease severity of 100, 74.03–97.57, 69.62–80.92, and 72.29–73.95% in resistant, moderately resistant, susceptible and highly susceptible varieties, respectively. A strong positive correlation was observed between disease severity and TGW loss during the cropping season 2019, 2020 and pooled data. The grain yield was enhanced, and crop loss models indicated good fitness with excellent predictive validity for estimating sheath rot impacts. As the first systematic assessment in northern region of India to systematically assess the impact of rice sheath rot. Its findings provide crucial insights into the interaction between fungicide treatments, varietal resistance, and disease dynamics, paving the way for more informed and effective management strategies in the region.