Combining Ability and Heterosis for Grain Yield and Other Agronomic Traits in Provitamin A Enriched Maize Inbred Lines

Combining ability of enriched Pro-vitamin A yellow maize inbred lines can provide information for breeders to develop biofortified maize hybrids with high yield and desirable traits. Sixty-eight F1 hybrids along with two checks were arranged in alpha lattice design, replicated twice and evaluated across three locations at mid-altitude agro-ecology of Ethiopia. The combined analysis of variance revealed a significant difference (P ≤ 0.01) in mean square due to PVA hybrids, environment and hybrid interaction with environments for grain yield and most of the agronomic traits and it indicates that genotypes performed differently across environments. Seven PVA hybrids were selected based on average yield performance ranging from 7.11 to 7.95 t/ha and 18.69–29.04% yield advantage over the best check and these hybrids should be further evaluated across environments. The mean squares analysis of variance for GCA and SCA showed a significant difference (p ≤ 0.001) for all traits studied, indicating that both additive and non-additive gene effects were important for controlling these traits. Significant positive SCA effect on grain yield was recorded for crosses of L7/L12 (3.16 t/ha), L7/L9 (2.43 t/ha) and L10 x L12 (2.05 t/ha). Only one cross (L9 x L12) displayed significant (p < 0.05) positive standard heterosis (34.52%) over BH 549, whereas non-significant positive heterosis was detected over the BHQPY 545 check. Inbred lines L12, L8, L6, L10, and L2 had the highest positive and significant GCA effects on grain yield and other traits. Out of these lines, L8 and L12 were good combiners for most traits and will be used as alternative testers as they had the highest GCA effect for yield as well as other traits, and also their cross combination were among the top performing hybrids for yield. Our study highlighted that those inbred lines that had a high GCA effect within the heterotic group, could be used as a new source of PVA inbred line development. Furthermore, L8 and L12 can be used as alternative testers for future PVA maize breeding programs.