The genetic potentials of resistance to turcicum leaf blight (TLB), grey leaf spot (GLS), and common rust (CR) disease, grain yield and selected agronomic trait were studied in 45 F1 hybrids from a half diallel following Griffing’s Model 1, Method 4. The 45 hybrids excluding parents were evaluated in 5 × 9 alpha lattice designs with three replications. The study was carried out at Jimma Agricultural Research Center during 2015 cropping season with the objective to evaluate combining ability for turcicum leaf blight, grey leaf spot, common rust disease, grain yield and selected agronomic trait in maize inbred lines. For analysis of variance, days to 50% anthesis, days to 50% silking, turcicum leaf blight, grey leaf spot, common rust disease severity index, days to maturity and grain yield data were collected. Mean square due to general combining ability (GCA) was highly significant (P ≤ 0.01) for all traits, while specific combining ability (SCA) mean square was non-significant except for grain yield, days to 50% tasseling, days to 50% of silking, and days to maturity. This study showed the importance of additive types of gene action in controlling the inheritance of the traits. Among ten inbred lines, L7 and L10 were best combiners for GLS tolerance with the highest negative value of GCA effects and inbred line L7 was the best combiner for TLB and CR tolerance with the highest negative value of GCA effect. Inbred lines L2 and L9 were best combiner for grain yield with the highest positive GCA effect value. Therefore, maize breeding program can engage in hybridization and synthetic variety formation based on the information of inbred lines with high negative value GCA effect for diseases tolerant and high GCA for grain yield.
Key words: Combining ability, general combining ability (GCA), inbred lines, specific combining ability (SCA).
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