Rice blast caused by Pyricularia grisea (Cooke) Sacc. became one of the most important disease in rice growing areas of Telangana State because of its wide distribution and destructiveness under favourable conditions. However, sometimes resistant varieties may become ineffective due to evolutionary changes in the pathogen population. Keeping in view the importance of disease, studies were conducted on cultural and morphological variability of P. grisea isolates. Blast infected samples were collected from different locations of Telangana State were studied for radial growth, colony color, growth pattern, texture of colony, sectoring, zonation and wrinkles formation, dry mycelial weight, time of sporulation and sporulation index. The highest mean radial mycelial growth of the fungus was recorded on OMA (81.7 mm) followed by PDA (77.8 mm) and least mean radial mycelial growth of the P. grisea isolates were recorded on HLEA medium (72.5 mm). Colony colour of twelve P. grisea isolates were differed from greyish white to greyish black on three solid media tested. All the isolates were circular form and varied with respect to mycelium elevation and texture. Significant differences were also observed among the isolates with the formation of sector, zonation and wrinkles. Among the three different liquid media tested, highest mean mycelial dry weight of the P.grisea isolates was recorded on PDB (225 mg) followed by OMB (214 mg) and least mean mycelial dry weight on HLEB(164 mg).Time taken for sporulation of P. grisea isolates on OMA medium was 7.9 days followed by HLEA medium for 8 days and PDA medium for 8.2 days. Sporulation index of twelve P.grisea isolates were varied from poor to excellent on rating scale of 1 to 4 on three solid media tested. Conidia of the isolates were produced in clusters on long septate, slender conidiophores. The mean conidial size ranged from 18.9 μm to 28.2 μm in length and 6.1 μm to 9.3 μm in width among twelve P. grisea isolates. The shape of conidia in all the isolates was pyriform and hyaline to pale olive, 2 septate and 3 celled. Spore germination percentage was high in Pg1 isolate (91.6 %) and least in Pg6 isolate (28.3 %).

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