Studies of Nonrandom and Barren‐Type Sterility in Sorghum bicolor 1

The frequency of nonrandom‐type sterile Sorghum bicolor (L.) Moench plants among the progenies of random‐type sterile plants in the S 1 , S 2 , and S 3 generations decreased with advancing generations. The progenies of non‐random‐type sterile plants became more uniform, suggesting genetic control of such sterility. Barren‐type sterility was observed in S 1 S 2 , and S 3 generation sorghum plants. The breeding behaviors of the segregating progenies suggested that this character was controlled by two gene pairs and that the double homozygous condition resulted in the expression of recessive barren‐type sterility. Fourteen progenies segregated for 15 nonbarren to 1 barren‐type sterile plants as expected. Eight progenies showed good agreement to a 3:1 ratio, and five progenies had an excess of barren‐type sterile plants. These findings further suggested that the genes governing barrenness are expressed only under certain environmental conditions.