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.

Wheat powdery mildew, caused by the obligate biotrophic fungus Blumeria graminis f. sp. tritici ( Bgt ), is a devastating disease responsible for substantial global yield reductions. Host resistance offers the most sustainable management strategy, yet its durability is continually undermined by high evolutionary potential of the pathogen, driven by sexual recombination and rapid mutation. To decipher long-term virulence dynamics, we conducted a comparative analysis of Bgt populations in the Northwestern Himalayas over two decades (1994–1998 and 2015–2019). Pathotype profiling of 285 isolates on a common set of nine differential lines revealed a significant shift in virulence structure over time. While the mean virulence complexity per isolate increased in the contemporary population, indicating enhanced pathogenic capability, overall pathotype diversity decreased, suggesting a selective sweep toward fewer, more aggressive lineages. Marked changes in virulence frequency were observed with severe efficacy erosion for Pm1a (virulence increased from 6 to 63%) and Pm8 , while virulence against Pm2 , Pm3a , and Pm3b declined significantly. Notably, genes Pm2 and Pm4a demonstrated complete and durable effectiveness throughout the study period. Our results identify these as stable resistance donors and underscores the continuous adaptation of Bgt populations. This study provides critical insights for designing durable resistance gene pyramids and underscores the necessity of continuous virulence surveillance to sustain wheat production in the face of evolving pathogen threats.