It has been proposed (MNL 47:35-37) that nuclear fertility restorer genes in plants treated with chemical mutagens may disguise an induced cytoplasmic male sterile (i.e., a sterile cytoplasm may be induced with a mutagen but still produce fertile plants due to the presence of nuclear restorer genes). Previously reported research (MNL 50:28-29) was with the inbred A632. According to Gracen and Grogan (MNL 48:20-23) and Gracen (personal communication), this inbred has restorer genes for many different sterile cytoplasms; therefore, it could also carry restorer genes for sterile cytoplasms that might be induced with chemical agents. To examine this idea, an inbred that does not restore many sterile cytoplasms should be chosen, and the inbred W59M was suggested by Gracen.

Seeds of inbred W59M were germinated for 30 hours on Kimpak at 27 C; at the end of this time some radicles had emerged. The germinated seeds were placed in petri dishes on Kimpak saturated with the mutagen: streptomycin in doses of .001%, .005%, .01%, .05%, .10%, .15% and control, and ethidium bromide in doses of .001 M, .005 M, .01 M, .05 M and control; all treatments were conducted for 24 hours at approximately 22 C. The treated material was planted in trenches in the field, watered and then covered. The M1 plants were self-pollinated in 1975 and planted ear-to-row in 1976. Among 128 M1 and approximately 3840 M2 plants from the streptomycin treatment and 91 M1 and 2730 M2 plants from the ethidium bromide treatment, no male steriles were detected. Since no male steriles were found, the value of using nonrestoring inbreds cannot be determined.

Robert W. Briggs

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