Abstract

Breeding efforts to develop high yielding and improved maize varieties for highland areas (altitude of 1700- 2400 m) has been recently, launched in Ethiopia. In Ethiopia, national average maize yield under farmer condition is far below attainable. Thirty-four crosses (seventeen inbred lines and two testers) along with two popular standard checks were evaluated for 17 traits in alpha lattice design at Jimma, Dedo. The objectives of this study were to evaluate top cross performance and to estimate combining abilities for grain yield and related traits. The inbred lines and crosses differ significantly for all of the studied traits except ASI, NPP and EPP. Among the crosses L5 × T1 and L16 × T2 showed higher grain yield, crosses L14 × T1 (158.13 cm), L6 × T2 (168.54 cm) expressed short plant height, crosses L4 × T1 (L16 × T1 (231.04 cm) and L14 × T1 (258.13 cm) expressed higher plant height. Crosses L5 × T1 (102.63 day) and L2 × T2 (107.95 day) displayed lowest an thesis date and crosses L5 × T1 (112.67 day), L2 × T2 (114.29 day) displayed lowest silking date. GCA mean squares due to lines were highly significant for most of the traits, while SCA mean squares were significant for some traits. The higher the percentage relative contribution of GCA sum square over SCA sum of square in all studied trait indicated the predominance of additive gene effect in controlling the inheritance of these traits. For grain yield inbred lines L5, L6, L16 and L17 were the top general combiner. Lines with positive and significant GCA effects for grain yield were generally considered as good general combiner for improvement of grain yield. L2, L5, L17 were the best general combiners for days to anthesis. L2, L5, L17, L12, L14 for days to silking and L11 for tallness, while L2, L6, L12, L13, L8, L5, L14 for shortness in plant height were the top general combiner. Future studies should explore the possibility of separating the inbred lines used in this study into distinct heterotic groups using divergent tester. By and large, the information from this study could be useful for researchers who need to develop high yielding varieties of maize adapted to the highland area of Ethiopia.

Keywords: Combining ability; Line × Tester; SCA; GCA; Maize inbred lines; Ethiopia