Morpho-Cultural Variability Characterization of Bipolaris oryzae Causing Brown Leaf Spot of Rice in Jammu Sub-Tropics

Extensive fortnightly surveys were undertaken in major rice growing districts of Jammu division to study cultural and morphological variability amongst the isolates brown leaf spot disease causing fungus (Bipolaris oryzae). Based on severity 24 (BO1 BO24) divided into three groups (I, II III). Group ‘I’ comprised 11 with values between 51.22-67.44% categorized under highly virulent group ‘II’ 43.17-48.17% moderately isolates. ‘III’ included eight value 26.11-38.17% less On basis colony growth pattern, margin colour, 4 (A, B, C D). A six had entire margin, circular form, umbonate elevation smooth surface black fluffy growth. Eleven categorised B developed colonies undulated irregular grey greyish colour. surface. D contained four form; raised wrinkled surface, mycelium was which turned showed pigmentation. The largest conidial size recorded isolate BO1 (98.43-101×24.54-25.54 µm). conidia mean septa 4.5-7.4 straight curve shaped. sporulation different B. oryzae ranged 6.1-7.6×106 spores/ml.