Four spring wheat [Triticum aestivum L. em. Thcll. ssp. vulgate (VilL, Host) Mac Key] cultivars, ‘Henry,’ ‘Thatcher,’ Wis. 255, and C.I. 12633, contrasting parents for kernel weight, were intercrossed in six combinations to estimate gone effect parameters, the extent of heterosis, and heritability for this character.
Hayman's (6) three- and six-parameter models utilizing generation means were used to estimate gene effects. Additive and dominance effects were more consistent and important in determining kernel weight than epistatic effects. However, epistasis was detected in at least 1 year in all crosses where the parents were of different kernel weight classes. Parents and environment influenced the expression of epistasis. Additive ✕ additive and deminance ✕ dominance types of epistasis were more important than additive ✕ dominance effects.
Heterosis, calculated as the percentage increase of F1 above midparent performance, ranged from −4.3 to 31.2%. Heterosis was greater in crosses of more distantly related parents and it usually occurred with significant dominance and one or more significant epistatic effects. Broad sense heritability estimates for kernel weight ranged from 51 to 85% over crosses and years, with one exception (9%).