Abstract: In vitro screening of seed-derived and microspore-derived callus lines was carried out by the biotechnology of plant cell culture, with the raw toxin extract of piricularia oryzae as stress factor.JR19 and other mutants resisting rice blast were otbtained.There were significant differences in the resistance to rice blast in seedlings and the esterase isozyme zymograms of embryoes between mutants and original varieties.Some resistant mutants in R2 were still able to resist rice blast in R3.These mutants were almost accompanied by variations in agronomic traits such as dwarfism, high sterility, heading date or grain weight. Most of the mutants were basically regular and consistent in R2 and relatively stable in R3. The efficiency and possible potential of screening resistant mutants in vitro and its use in resistant rice breeding were discussed. The procedure of screening resistant mutants in vitro was suggested.