Combining Ability for Drought Tolerance in Maize (Zea mays L.) Using Line x Tester Analysis

摘要

Seven white maize inbred lines (L_2, L_5, L_(10), L_(20), L_(46), L_(51) and L_(52)) derived during an inbreeding program by the Genetics and Plant Breeding Group, Genetics and Cytology Department, National Research Center (NRC) were crossed with fivetesters (Tri hybrid variety TWC310, Tl; double cross variety Taba, T2; drought-tolerant synthetic variety Giza 2, T3; single crosses S.C. 10, T4; a local open-pollinated cultivar Nab El Gamal, T5) to estimate combining ability and type of gene action under normal and drought stress to identify the desirable lines that could be used in a hybrid breeding program for future utilization and studies. The selection index revealed that the best desirable crosses for grain yield and most agronomic characters were the crosses 'TWC310' x L_2, 'TWC310' x L_(20), 'Taba' x l_(51) and 'Taba' x L_(46) under normal and drought environments. Significance of mean squares of genotypes, crosses, parents, parents vs. crosses, lines, tester, and the line x tester interaction for most studied traits under both conditions indicated that the crosses performed significantly better than their respective parents and therefore heterotic effects were present. Results of general combing ability (GCA) effects indicated that the lines L_2, L_(20), L_(51), and L_(52) under normal and drought stress conditions seem to be good general combiners for increasing yield and yield components of hybrids. On the other hand, the testers 'TWC310' and 'Taba' displayed highly significant positiveGCA effects, which has interest in breeding programs for developing high grain yield/plant and one or more of the remaining traits under normal and drought environments. The best hybrids 'TWC310' x L_5, 'Taba' XL_5, 'Nab El Gamal' x L_(52), and 'SC10' xL_2 showed significantly high positive specific combining ability effects for yield/plant and most yield components under drought. Thus, we recommend further testing of these new inbred lines for use in a crossing program so as to combine major yield components with high yield under drought conditions.