Development of Resistance to Tricyclazole in Pyricularia grisea Sacc. in Southern Telangana Zone of Andhra Pradesh

Sensitivity of nine of Pyricularia grisea Sacc. collected from different rice growing areas in Southern Telangana Zone of Andhra Pradesh was studied in vitro conditions. Mahabubnagar isolate (Pg₅) recorded the highest ED₅₀ value of 118.51 μg ml⁻¹ and the MIC 500 μg ml⁻¹. Ranga Reddy isolate (Pg₁) recorded the lowest ED₅₀ value of 96.10 μg ml⁻¹ and MIC value of 250 μg ml⁻¹ which was nearly equal sensitive as reference sensitive isolate (Pg₃). Pg isolate recorded the next highest EDvalue of 110.41 μg ml⁻¹ with MIC of 250 μg ml⁻¹ followed by Pg (104.66 μg ml⁻¹) and Pg₈ (104.26 μg ml⁻¹) in the decreasing order of their resistance. The MIC value for both Pg₉ and Pg₈ isolates was 250 μg ml⁻¹. Isolate Pg₂ recorded the next lowest ED₅₀ value of 99.22 μg ml⁻¹ with MIC value of 250 μg ml⁻¹ followed by Pg₆ with ED₅₀ value of 101.81 μg ml⁻¹ and Nalgonda isolate (Pg₇) with ED₅₀ value of 104.26 in the increasing order of their resistance.The results showed that the fungus is under high selection pressure leading to evolution of tricyclazole resistant population.