Estimates of combining ability in seven new yellow maize inbred lines for grain yield and some agronomic traits

Diallel crosses among seven advanced yellow maize inbred lines derived from different maize populations without reciprocals were made in 2015 season at Mallawi Agricultural Research Station, Minia, Egypt. The resultant 21 crosses along with two commercial check hybrids i.e. SC 162 and SC 168 were evaluated in a Randomized Complete Block Design with four replications at two locations i.e. Mallawi and Sakha Stations, Egypt during 2016 summer season. Mean squares due to crosses, G.C.A. and S.C.A. were significant for all studied traits. The ratio of G.C.A. variance to S.C.A. variance exceeded the unity for all studied traits, except for number of kernels per row, indicating that the greater importance of the additive gene effects than the non-additive gene effect in the inheritance of these traits. The parental lines 3, 5 and 7 had significant positive GCA effects for grain yield, in addition lines 5 and 7 had significant negative (preferred) GCA effects for days to 50%  silking. Also, inbred line 4 had negative significant GCA effects for both 50% silking and plant height. Nine crosses (P1xP3, P1xP4, P1xP7, P2xP6, P3xP4, P4xP5, P4xP7, P5xP6 and P6xP7) showed significant positive SCA effects for grain yield. Among these crosses, Three crosses (L₁ × L₄, L₂ × L₆, L₄ × L₅) exhibited the highest SCA effects and also its gave the highest mean performance for grain yield. These crosses may be released as commercial hybrids by the Maize Research Program after further testing and evaluation. Despite cross (L₁ × L₄) was insignificant higher than SC.168 but was significantly earlier and relatively shorter. The crosses (L₁ × L₇) and (L₂ × L₅) had higher yield, while, the first one was significantly earlier than SC.168, while the second one was significantly shorter than SC.168. These promising single crosses should undergo more testing across years and location before submission to the Varity Registration Committee, (VRC).