Abstract

Information on combining ability and heterotic grouping for newly developed inbred lines is of paramount importance to design future breeding strategies for the development of hybrid and synthetic varieties. The objectives of the present study were to examine combining ability and to determine heterotic groups of the inbred lines for grain yield and other desirable traits. Twenty five inbred lines were used for the formation of the experimental crosses using line x tester mating design. The resulting 50 F1 crosses plus two standard checks (BH540 and BH543) were evaluated at Bako, Western Ethiopia in 2012 main cropping season. The entries were arranged in alpha lattice design with three replications. Data on grain yield, other agronomic traits and disease reactions were recorded under field condition. The highest grain yield was recorded from L24 x T1 (CML312/CML442) (9.97 t ha-1). The analysis due to mean squares for crosses was highly significant for all traits except for plant aspect, ear per plant, and number of plants per plot, and thousand kernel weights indicating the existence of genetic variability for all traits. GCA of line was significant for grain yield, agronomic traits and disease severity index. The mean square due to SCA for line by tester combinations were also significant for grain yield, stalk lodging, root lodging, ear rot, husk cover, maturity date, 50% silking day, and Turcicum leaf blight. Significant GCA and SCA effects were indicative of the importance of both additive and non additive gene effects in the control of the traits. However, in all traits, the proportion of GCA sum of square was higher than SCA sum of squares indicating the preponderance of additive gene effects in the control of all traits. Based on the SCA of crosses, the two testers used in this study successfully classified nine out of 25 tested inbred lines into two heterotic groups, A and B: six inbred lines belong to heterotic group A, while the remaining three belong to h