COMBINING ABILITY AND TYPE OF GENE ACTION FOR GRAIN YIELD AND SOME OTHER TRAITS USING LINE X TESTER ANALYSIS IN NEWLY YELLOW MAIZE INBRED LINES (Zea mays L.).

Abstract

Fourteen newly yellow inbred lines of maize were topcrossed with the two inbred line testers; Giza-638 and Giza-649 at Sids Agricultural Research Station in 2005growing season. The 28 topcrosses in addition to two yellow single crosses; SC 155 and SC 3084 as check varieties were evaluated in 2006 season at two locations; Sakha and Sids Agric. Res. Stns. The studied traits were number of days from planting to date of 50% silking, plant height, ear height, infection of late wilt% disease, number of ears/100 plants and grain yield in (ard/fed). Highly significant differences were found between the two locations for the studied traits, these finding indicated that the traits differed from one location to another. Significant and highly significant mean squares for crosses, lines and testers were observed for all studied traits. Mean squares of lines x testers interaction were highly significant for silking date, no. of ears/100 plant and grain yield. Interactions between crosses, lines, testers and line x testers with locations were not significant. The parental inbred lines that exhibited desirable general combining ability (GCA) effects were L4, L5, L7, L12, for plant height toward shorter plants and ear height toward lower ear placement. Line-4 had negative and significant GCA effects for 50% silking toward earliness, L5 for grain yield, L9 for no. of ears/100 plants, L10 for no. of ears/100 plants and grain yield, L14 toward earliness and grain yield and L2 for grain yield. Generally, these inbred lines could be recommended for advanced stage of evaluation by maize program. Giza-638 (T1) tester was good general combiner for days to 50% silking toward earliness and ear height toward lower ear placement. While, Giza-649 (T2) tester was good general combiner for no. of ears/100 plants and grain yield. The highest SCA effects were observed in the topcrosses L8 x T2, L13 x T1 and L14 x T1 for grain yield, L8 x T2 and L9 x T2 for no. of ears/100 plants, L7 x T1 for infection of late wilt% and L12 x T2 for earliness. Estimation of general combining ability variance components (2GCA) was larger than that of specific combining ability variance components (2SCA) for silking date, plant height and ear height, indicating that additive was found to be more important than non-additive gene action for these traits. While, the 2SCA was larger than 2GCA for infection of late wilt%, no. of ears/100 plant and grain yield, indicating that the non-additive genetic variance played the major role than additive genetic variance in the inheritance of these traits. Topcrosses were significantly superior to the check SC 3084 (26.66 ard/fed) for grain yield, silking date (toward earliness), plant height (toward shorter plants) and ear height (toward lower ear placement). Generally, eight topcrosses; L8 x T2 (37.44 ard/fed), L14 x T1 (37.40 ard/fed), L2 x T2 (36.05 ard/fed), L10 x T1 (35.96 ard/fed), L9 x T2 (35.32 ard/fed), L5 x T1 (35.24 ard/fed), L13 x T1 (34.89 ard/fed) and L11 x T2 (34.76 ard/fed) were superior to the check SC 155 (34.08 ard/fed) for grain yield. Also, the three topcrosses; L2 x T1 (34.27 ard/fed), L6 x T1 (34.24 ard/fed) and L10 x T2 (34.53 ard/fed) were highly mean of grain yield, but they were not significant different from than the highly check SC 155.