[en] The popular high yielding variety, Ratna (IR 8 x TKM 6), with a duration of 110 days, is susceptible to blast disease, (Pyricularia oryzae). Dehusked seeds of Ratna were pre-soaked in distilled water for 4 hours and then subjected to 0.1% and 0.2% EMS for 6 hours. The percentage of germination was lower in 0.2% EMS but survival higher. Seedlings of M₁ were raised in pots and panicles of individual plants were harvested separately for M₂ generation. The seeds of M₂ generation were grown in ''Uniform Blast Nursery'' for observing blast disease reaction. Seeds of resistant plants were harvested and grown in M₃ generation. Some susceptible plants were also carried forward to M₃ generation. Ratna control (untreated) developed ''B'', ''C'' and ''D'' type spots. The EMS treated population (8000 plants) developed in addtion, ''O'', ''A'' as well as ''E'' type spots, showing a wider range of variability than the untreated control regarding resistance and susceptibility. Three hundred resistant plants (with ''O, ''A'' and ''B'' type of spots) from M₂ were carried forward to M₃ generation. These also segregated giving a range of reaction from 0-E spots as in the case of M₂. The population of resistant plants was higher in M₃ (31.65%) than in M₂ (23.6%). The progenies of a few plants (50 plants) found susceptible in M₂ also segregated in M₃ towards resistance, but the percentage of resistant plants was low (7.6%)