INHERITANCE OF MAIZE COMMON SMUT RESISTANCE

Abstract

Eight white maize inbreds, namely L 120, L74, L 144, L56, L 82, L 71, L 85 and L 173 and 28 F1 maize crosses derived from a half diallel cross among these white inbreds, in addition to S.C. 10 check hybrid were evaluated for their resistance to the common smut disease and also for their grain yield (ardab/feddan) in two seasons. Artificial infection was applied using Ustilago maydis spore suspension (at 5 x 105 sporidia /ml. which was injected into the ear heads (2 ml per ear head) 4 to 7 days after the silking stage). Also, two sowing dates were applied. The results indicated that there were significant differences among the genotypes, parents, crosses and parent vs. crosses for disease incidence (DI), disease severity (DS), total soluble solids (T.S.S.), percent yield reduction and grain yield (ardab/feddan). The parental inbred lines L3 and L4 and their F1 crosses L3 x L4, L3 x L6, L1 x L3, L2 x L4 and L3 x L5 exhibited the lowest values of DI, DS and percent yield reduction with higher values of T.S.S. and grain yield and classified as more resistant to common smut disease than other lines and therefore considered the promising ones. Disease incidence and DS were lower in early sowing than late one. Variances due to general combining ability (GCA) and specific combining ability (SCA) was highly significant for all the studied characters under the two sowing dates. The additive gene action was more important than the dominance one in the inheritance of common smut resistance measurements, but the non-additive gene action was adequate in the inheritance of grain yield in both sowing dates. Inbred lines (L1), (L2), (L3) and (L4) significantly exhibited negative GCA effects. Hereby these inbreds were the best general combiners for common smut resistance characters, while the inbred lines (L2), (L3), (L5) and (L6) were the best for grain yield. The single crosses (L1 x L8), (L2 x L3), (L3 x L4), (L4 x L6), (L4 x L8) and (L6 x L8) could be recommended to be used in maize breeding program for resistance to common smut disease and high grain yield.Heritability in narrow sense was high (> 50%) for DI, DS and percent yield reduction; moderate (30-50%) for T.S.S. and low (< 30%) for grain yield.