Combining ability for some inbred lines in half-diallel crosses of maize under two different locations conditions

A half diallyl cross among eight new yellow maize inbred lines, i.e. Gm. 142, Gm. 224, Gm. 233, Gm. 152, Gm. 297, Gm. 330, Gm. 201, and Gm. 303, was made in 2015 summer season. Twenty eight F1 crosses along with two yellow commercial check hybrids, SC162 and SC168 were evaluated in randomized complete block design with four replications at two locations (Gemmeiza, Gharbia and Sids, Bani Sweif, Egypt) in 2016 summer season to study the combining ability to identify the most superior parental inbred lines that produce superior hybrids and develop high yielding new yellow single crosses. Results indicated that mean squares of crosses exhibited significant or highly significant for all studied traits. Mean squares due to GCA and SCA were significant or highly significant for all studied traits at combined over the two locations, except GCA for ear diameter trait and SCA for ear length trait, which were non-significant. The ratio of GCA/SCA was more than unity for all studied traits at combined over the two locations, except days to 50% silking and ear diameter traits, indicating that additive gene was more important than non-additive gene action. The interaction between GCA and SCA and locations were highly significant for all studied traits, except GCA x Loc. for ear diameter trait and SCA x Loc. for ear length trait. The magnitude of the interaction was highest for GCA × locations than the SCA × locations for plant height, ear height, ear length and grain yield, indicates that additive genetic variance was influenced by environment and the additive component interacted more with the environment than the non-additive and vice versa for days to 50% silking and ear diameter. According to analysis of GCA effects, the best general combiners were P3 (Gm.233) for earliness; P4 (Gm.152), P5 (Gm.297), P6 (Gm.330) and P7 (Gm.201) for plant height (shortness); P5 (Gm.297), P6 (Gm.330) and P7 (Gm.201) towards lower ear position; P4 (Gm.152) and P6 (Gm.330) for ear length; P1 (Gm.142) for ear diameter; and P1 (Gm.142), P5 (Gm.297) and P8 (Gm.303) for grain yield. Based on mean performance and SCA effects analysis, there were seven crosses No. 1, 2, 5, 7, 9, 25 and 26 (P1 x P2, P1 x P3, P1 x P6, P1 x P8, P2 x P4, P5 x P8 and P6 x P7) were the best combinations where they recorded significant or highly significant positive SCA effects for grain yield.