Reciprocal differences were found for tassel date, silk date, plant height, ear height, shank length, husk extension, tip blanking, row number and ear length in a diallel cross of 7 sweet com inbreds (Zea mays L.). Reciprocal differences were not detected for first ear weight. Reciprocal differences were large enough in some crosses to have important breeding implications.
Tassel date, silk date, plant height, ear height, shank length, husk extension, tip blanking, row number, ear length, and first ear weight were studied in a diallel involving 7 inbred sweet corn parents. Both general combining ability (GCA) and specific combining ability (SCA) were involved in the inheritance of all 10 characters. This was consistent for F1 crosses in 2 years and for F2 families. SCA variance (VSCA) was larger than GCA variance (VGCA) for ear length and first ear weight in the F1 and ratios of VSCA/VGCA for these characters were slightly larger than 1.0. VGCA was larger than VSCA all other characters in the F1. Ratios of VSCA/VGCA ranged from .05 for row no. to .57 for plant height.
Variance ratios for most characters decreased in the F2. The failure of some ratios to decrease in the F2 was attributed to either differential interactions of GCA and SCA with environment or inadequate sampling of F2 families. Genotype × year interactions influenced the expression of most characters. A greater portion of the genotype × year interaction was contained in estimates of SCA than in estimates of GCA. Heritability estimates from parent-progeny regression were generally larger than those from variance components, although these estimates were generally in close agreement.