Effect of Different Levels of Seed Infection by Bipolaris sorokiniana on Leaf Blight Severity, Grain Formation, Yield and Subsequent Seed Infection of Wheat

Effect of different levels of seed infection by Bipolaris sorokiniana on leaf blight severity, grain formation, yield and subsequent seed infection of wheat was studied in vitro and in vivo with six treatments viz. T₁ (0% seed infection), T₂ (5.1–15% seed infection), T₃ (15.1–25% seed infection), T₄ (25.1–35% seed infection), T₅ (35.1–45% seed infection) and T₆ (45.1–60% seed infection). Leaf blight severity (0–5 scale) on flag leaf and second top leaf was recorded in flag leaf stage, panicle initiation stage, flowering stage, milk stage and hard dough stage. Leaf blight severity increased in the field with the increasing level of seed infection. A positive relationship was found between leaf blight severity and crop age. Number of grains/ear and number of healthy grains/ear were the highest in plots of T₁ while number of diseased grains/ear was the highest in T₆. Weight of grains/ear and weight of healthy grains/ear significantly increased with decreasing of seed infection level. In respect of grains/ear of different severity grades (0–5), the maximum Grade-0 seeds were found in T₁ and the maximum Grade-5 seeds were recorded in T₆. The highest grain yield (3.67 t/ha) and straw yield (6.41 t/ha) were recorded in T₁, where grain yield increased up to 38.69% over T₆. The incidence of B. sorokiniana on harvested seeds increased with the increasing levels of seed infection in the seed samples used during sowing.