Heterotic Response for Vegetative and Mature Plant Characters in Grain Sorghum, Sorghum bicolor (L.) Moench1

Abstract

Comparative expressions of heterosis for 13 vegetative and mature plant characters were examined from 24 F1 hybrid populations of grain sorghum. Significant average heterosis was expressed by the hybrids for grain yield, mature plant height, stalk diameter and for measures of height and leaf number taken at a vegetative growth stage. Hybrids also exhibited longer and wider leaves giving more area per leaf, earlier blooming, more seeds per head, increased numbers of heads per plant and larger seed, but significance was not shown for the hybrid advantage in comparison with the parental means.Significant variation among hybrids for percentage heterosis was expressed for all characters except stalk diameter, seeds per head and heads per plant. Greatest heterotic response was observed for grain yield where hybrids averaged 122% of the mid‐parent values, with a range of 106 to 147% among individual hybrids.Variance analyses indicated that general combining ability effects were more often significant than were specific combining ability effects. However, significance for the s.c.a, component was shown for 6 of the 13 characters, and the mean square for parents vs. hybrids was significant for 5 of the characters, indicating that non‐additive gene effects were important in the expression of these traits.Inter‐character correlations among hybrids indicated that seeds per head was the character most highly associated with grain yield. Correlations between the mid‐parent mean and hybrid performance were significant for each character, but the coefficients for many of the characters were not large enough to indicate that mid‐parent values would be highly effective indicators of hybrid performance.