Yield performance of wheat genotypes for resistance to spot blotch caused by Bipolaris sorokiniana (Sacc.) Shoemaker

Spot blotch of wheat, caused by Bipolaris sorokiniana (Sacc.) Shoemaker, is an important wheat disease in Nepal. The purpose of the study was to assess wheat genotypes for resistance to the spot blotch and their yield potential in field conditions. A field trial was conducted with 100 wheat genotypes using an alpha-lattice design with two replications, under natural conditions at the National Maize Research Program, Rampur, Chitwan, Nepal. Disease assessment was performed using both double-digit (recorded four times at eight-day intervals) and single-digit (recorded three times at three-day intervals) scales. The single-digit visual scoring for the flag and flag-1 leaves began 97 days after sowing. Genotypes were categorized based on the final disease severity of the flag leaves. The genotypes differed significantly (p<0.001) for resistance to spot blotch. Of the 100 genotypes, one (NRN35) was found moderately resistant, 19 were moderately susceptible, 60 were susceptible, and 20 were highly susceptible. The plot grain yield (482 g) of NRN35 was the second highest among genotypes. A significant negative correlation (p<0.001) between the Area under disease progress curve and yield-attributing traits was found. In addition, a strong positive correlation (r = 0.762, p<0.001) was found between the disease incidence in the flag-1 and flag leaves. This study identifies NRN35 as a promising genotype that combines moderate resistance with high yield, making it a valuable candidate for wheat improvement programs. Its performance under natural disease pressure underscores the potential for developing spot blotch-resilient varieties through strategic breeding.