Analysis of a cyclic gametic selection procedure in Sorghum bicolor (L.) Moenich

Vita.A study was initiated in the spring of 1973 to evaluate the effectiveness of a cyclic gametic selection prodedure in Sorghum bicolor (L.) Moench in extracting superior gametes from a random-mating population and the subsequent improvement of the elite inbred line used as the selector inbred. Utilization of fall nurseries in Puerto Rico enabled the completion of three full cycles of selection by the summer of 1976. The selector inbred was RTx2552, a yellow endosperm CaudatumKaura, into which the male-sterility inducing gene, ms₃, had been incorporated to facilitate crossing. RTx2552 is a widely adapted restorer line which combines well with the tester inbred. The tester inbred was ATx378, Redlan, which is a widely adapted cytoplasmic-genetic male-sterile line possessing good general combining ability. The random-mating population, TP4R, was used as the variable gametic source. TP4R was developed by the Sorghum Improvement Program of the Texas Agricultural Experiment Station and was derived from converted and partially converted lines from the TAES-USDA sorghum conversion program. Variable F₁ plants were produced by crossing RTx2552 x TP4R plants selected visually for agronomic desirability. Visually selected F₁ plants were selfed and crossed to ATx378 to produce "F₁-hybrids" which were evaluated in a replicated yield test in the spring of 1974. There were 109 "F₁-hybrids" of gamete selections tested against the check hybrid, ATx378 x RTx2552. Confidence limits (1% level) were placed on the check mean yield, and those hybrids that exceeded the upper limit, fell between the limits or failed to exceed the lower limit were classified as superior, intermediate, and inferior, respectively.