Combining ability and heterocyst of maize inbred lines

Abstract

Maize is one of the high priority crops to feed the ever increasing population in Africa, however, its production is limited by shortage of high yielding varieties coupled with biotic and abiotic stresses. Ambo Agricultural Research Center developed a number of inbred lines and crosses whose genetic information has not yet studied. This the study was initiated to estimate combining ability, heterosis, and traits association of maize inbred lines and crosses using line by tester analysis. Fifty entries consists 48 F1 single crosses developed from 24 inbred lines and 2 testers using line x tester design and two commercial check hybrids used in the study. The experiment was conducted using alpha lattice design with two replications at Ambo and Holeta Agricultural Research Center. Analysis of variance revealed existence of significant genetic variation among genotypes for all studied traits except for plant aspect (PA). Location x entry interaction for most of the traits was not significant which suggests hybrid performance was consistent across tested locations. Crosses L23 x T1 and L11 x T1 were the best performing genotypes for grain yield with mean values of 10.17and 9.50 t ha-1 , respectively. Line x tester analysis of variance showed that mean squares due to GCA of lines were significant (p< 0.01 or p< 0.05) for all studied traits. Mean squares of tester GCA and SCA were significant for most of studied traits. This indicates that additive and non-additive gene effects had contributed for the variation of the crosses. However, higher proportional contribution of additive gene action for all studied traits was obtained. Mean squares of GCA line x loc and GCA tester x loc interaction were significant for some of studied traits which implies that the trend of variation of GCA lines and testers were different across locations. Broad sense heritability ranged from 28.19 to 88.76% and majority of the studied traits showed medium to high heritability, indicating higher genetic effect than environmental effect. But, grain yield had lower broad sense heritability estimate of 28.19%. Number of ears per plant, ear height, ear diameter and number of kernels per row had positive association, and exerted positive direct and indirect effects on grain yield, indicating possibility of simultaneous improvement of these traits and grain yield. Several lines and crosses were identified as good general and specific combiners for yield and yield related traits. Lines L23, L11, L15 and crosses L2xT1, L3xT1, L8xT1, L11xT1, L23xT1 and L13xT2 were found to be good general and specific combiners, respectively. L11xT1 and L23xT1 had significantly higher standard heterosis for grain yield over the best hybrid check (Kolba) with values of 22.18% and 32.44%, respectively. Based on the direction of sca effects, 24 lines each were categorized under ‘’A’’ and ‘’B’’. In conclusion, better performing testcrosses, inbred lines with desirable gca effects and known heterotic groups, cross combinations with desirable sca effects and heterosis for grain yield and yield related traits could be used as source of useful genetic material for future maize breeding activities.