Cytoplasmic Male‐Sterility For Hybrid Sorghum Seed Production 1

NVES'TIGATIONS with three-way crosses as a method 1 for hybrid sorghum seed production have been reported previ~usly.~ All possible crosses between heterozygous (Msms) Day, Double Dwarf Yellow Sooner milo and Texas Blackhull kafir were made to determine if cytoplasmic factors might account for the F, male-sterility in the combination of msms Day x kafir. The evidence indicated that the F, sterility was genetic rather than cytoplasmic. The F, plants of milo x kafir and its reciprocal grown in 1949 were fully fertile. However, some partial male-sterility was observed the following year in small F, populations of milo x kafir but not in the reciprocal cross, kafir x milo. The defective anthers in partially male-sterile panicles were somewhat longer than those typical of malesterile Day. In the same year, in certain progenies of ms Day x kafir, F, male-sterile, crossed with various combine kafirs, some rows segregated in a ratio of approximately one fertile to one male-sterile as expected. However, most of the plants in other rows were sterile or partially sterile. Part of the plants in rows having excess male-sterility had the long, pinched-appearing anthers observed in the F,2 plants of milo x kafir. Since Day is derived from milo and presumably has milo cytoplasm, it was reasoned that the unexpected sterility might be accounted for if some degree of cytoplasmic male-sterility was being expressed in part of the populatioas. N o seed stocks of cytoplasmic male-sterile lines for distribution to producers have been developed but the results obtained 1:hrough 1952 warrant a preliminary report. Considerable interest in this material has been shown by visitors who have inspected the experiments in progress at this Station.