Heterosis and combining ability in diallel crosses involving maize (Zea mays) S1 lines

Abstract

This study was conducted at Egerton University, Njoro, Kenya for 2 growing seasons, 2001 and 2002. A diallel cross, without reciprocal crossings, involving 7 maize S1 lines: KSTP001, KSTP003, KSTP004, KSTP005, KSTP008, E2 and E3 was used to study the heterosis and inheritance of days to 50% flowering, plant height, ear height, leaf angle, number of leaves per plant, leaf area index, cob length, cob diameter, number of lines per cob, number of seeds per line, 100-grain weight and grain yield. A randomised complete block design with 3 replicates was used. Analysis of variance was conducted on the data generated at 0.05 significant level using MSTAT. The results showed that general combining ability (GCA) and specific combining ability (SCA) was significant (P<0.05) for all traits under study, suggesting existence of both additive and non-additive gene effects for the traits. However, GCA : SCA ratio was >1 for all traits except cob diameter and 100 seed weight, indicating preponderance of additive gene effects for inheritance of these traits. The study identified KSTP003 as the best combiner for most of the traits, while KSTP001 and E3 was the best combination for most traits. KSTP004 and E3 was good combiner for grain yield. Hybrid KSTP005 × E3 was the best cross for grain yield. KSTP003 × E2 was the best cross for reduction of leaf angle thus good source for erectophile canopies in a hybridisation program. Heterosis estimates showed that heterosis was more important in grain yield, yield components, plant height, number of leaves per plant and, leaf area index than other traits studied. Most of traits studied had a positive and significant (P≤0.01), while all traits studied except days to 50% flowering had a positive and significant (P≤0.01) genotypic correlations. It is recommended that based on their combining ability the lines be recombined to form synthetic maize varieties which can be released both as a variety or used for further improvement using recurrent selection. The lines which combine well for reduction in leaf angle from vertical should be utilised to develop erective maize varieties.