Combining Ability Effects for Forage Residue Traits in Grain Sorghum Hybrids1

Combining ability effects of 10 female and 10 male inbred lines were evaluated for agronomic, grain, and forage residue traits in 100 grain sorghum [Sorghum bicolor (L.) Moench] F1 hybrids for 2 years. Traits studied were height, flowering, tillering, seed weight, yield, protein percentage, protein yield of grain, leaves, and stems; and in vitro dry matter disappearance (IVDMD) percentage and digestible dry matter (DDM) yield of leaves and stems. General combining ability (GCA) effects exceeded specific combining ability (SCA) effects for all traits except height in females and grain and leaf yields in males. Both GCA and SCA were low for tillering and stem protein percentage. Genetic ratios, resembling heritability, were higher for GCA than SCA except for height in females and tillering in males. Grain yield generally had no extremely strong negatlve phenotypic correlatlons with any forage residue trait although grain yield correlated with stem protein and stem IVDMD percentages produced negative values that would warrant monitoring in a breeding program. Grain yield, stem and leaf yields, and stem and leaf DDM yields all had moderate to strong positive relationships with each other. A few potentially useful parents were identified having high GCA effects for forage quality characters. Data on protein and IVDMD percentages of leaf and stem fractions from grain sorghum breeding nurseries and hybrid yield trials should be routinely collected.