Date of Award
Doctor of Philosophy
R. E. Atkins
IAP1R sorghum (Sorghum bicolor (L.) Moench) random-mating population was constituted by using 80% adapted U.S germplasm and 20% converted exotic sorghums. After three cycles of mass selection for individual-panicle grain weight, forty S[subscript]2 families were selected from the population and crossed to three male-sterile inbreds ( A[subscript]1 Combine Kafir 60, A[subscript]1 Redbine 58, and A[subscript]1 Martin) to produce 120 single-cross hybrids. The experimental hybrids along with three commercial sorghum hybrids were grown in two years at two locations in Iowa. Measurements from the four environments for grain yield, seeds/panicle, 100-seed weight, panicles/plant, plant height and days to midbloom were analyzed to evaluate performance of the hybrids and to obtain estimates of general and specific combining ability effects of the male and female parents;Highly significant differences (P ≤ 0.01) were obtained for all traits for general combining ability (GCA) effects of the male parents and specific combining ability (SCA) effects. Highly significant effects for general combining ability of the female parents were expressed for grain yield, panicles/plant, and days to midbloom;For all traits, additive genetic effects of the male parents ( K[superscript]2[subscript]Am) were greater than additive genetic effects of the female parents ( K[superscript]2[subscript]Af). The K[superscript]2[subscript]Am effects were decidedly larger than dominance genetic effects ( K[superscript]2[subscript]D) for all characters, but the K[superscript]2[subscript]Af effects were slightly larger than the K[superscript]2[subscript]D effects for panicles/plant and days to midbloom, equal for grain yield, and smaller for the other traits;The four male parents (M8, M6, M16, M1) with the highest GCA effects for grain yield also had moderate to high GCA effects for seeds/panicle, plant height, and days to midbloom, and low GCA effect for 100-seed weight. Among the female parents, Combine Kafir 60 had the most desirable GCA effects for yield, seeds/panicle, 100-seed weight and plant height. Crosses with M8 and M16 were high yielding, but unacceptably tall. Crosses with M6 and M1 yielded 120% and 113% of the average of the commercial hybrids, respectively, and they exhibited favorable plant height and maturity. The hybrids with M2, M3, M10, and M26 also exhibited high yield and good agronomic characteristics.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Keith Richard Ess
Ess, Keith Richard, "Estimates of combining ability of S2 families derived from the random-mating sorghum population IAP1R " (1989). Retrospective Theses and Dissertations. 9121.