Heritability Estimates and Gene Effects for Agronomic Traits in Grain Sorghum, Sorghum vulgate Pers

Estimates of heritability and various gene effects were obtained for a number of agronomic traits in grain sorghum. The material studied included the parental lines and the F₁, F₂ B₁ (P₁ ✕ F₁), and B₂ (P₂ ✕ F₁), derivatives of the crosses ‘Redlan’ ✕ ‘Martin’, ‘Redlan’ ✕ ‘Combine 7078’, and ‘Plainsman’ ✕ ‘KS 7.’ It appeared that heritabilities of grain yield and kernel number were of lower magnitude than those of head weight, kernel weight, stalk diameter, and half blooming. Heritabilities of plant height and germination percentage were of a still higher order. The magnitude of heritability estimates varied greatly among crosses for some traits. Inadequacy of the original scale was indicated by a scaling test. Heritability estimates were also obtained based on logarithmically transformated data. Additive, dominance, and digenic epistatic gene effects were expressed in terms of parental, first and second filial, and backcrosses population means. Additive gene effects seemed to have a minor contribution to the inheritance for grain yield, head weight, kernel weight, and kernel number but appeared to be more important for other traits. Dominance gene effects seem to be important in the inheritance of most of the traits. Among the 3 types of epistatic gene effects it appeared additive ✕ additive and dominance ✕ dominance were important types of epistasis. Additive ✕ dominance gene effects were of minor importance, in general, except for germination percentage. The magnitude of additive ✕ additive gene effects was comparable to that of dominance gene effect and greater than additive gene effect. Dominance ✕ dominance gene effects were also of large magnitude. The effect of epistasis perhaps cannot be considered as negligible. Genetic models assuming negligible epistasis may be somewhat biased.