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Heterosis and Combining Ability in Maize using Diallel Crosses among Seven New Inbred Lines

Keywords: nitrogen , maize , General combining ability , additive , gene action , non-additive , specific combining ability , heterosis

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Abstract:

A half diallel cross between 7 inbred lines of maize was evaluated under two different nitrogen rates for six quantitative characters. Nitrogen rates, genotypes, parents, hybrids and parents vs crosses mean squares were significant for all traits. Significant genotypexnitrogen rate mean squares were obtained for days to 50% maturity, No. of rows ear-1 and shelling%. Significant interaction mean squares between hybridsxnitrogen rates were detected for days to 50% maturity, No. of rows ear-1 and grain yield plant-1. General and Specific Combing Ability (GCA and SCA) mean squares were significant for all traits. GCA/SCA ratios revealed that the additive and additivexadditive types of gene action were the most important expressions for days to 50% maturity, number of rows ear-1 and shelling% in both and nitrogen rates and combined analysis. Significant interaction mean squares between nitrogen rates and GCA and SCA were detected for most traits. The crosses P1xP2 and P1xP7 at the low nitrogen level, P1xP4, P1xP6, P1xP7 and P2xP5 hybrids at the normal nitrogen level and the hybrid P1xP7 in the across nitrogen levels, were out yielded the check hybrid (Pioneer 30K8). Also, single cross P1xP7 did not differ significantly from the hybrid Hytech 2031 in low nitrogen rate and combined analysis for grain yield plant-1. The parental inbred line No. 4 gave a good combiner for No. of rows ear-1 and grain yield plant-1 at both and across nitrogen rate. The most desirable inter and intra allelic interactions were presented by combinations: P1xP6, P1xP7, P2xP6 and P5xP6 for 100-kernel weight, P1xP2, P1xP4, P1xP6, P1xP7, P2xP3, P2xP5, P2xP7 and P4xP7 for grain yield plant-1 and P1xP4 and P4xP7 for shelling%. These crosses may be prime importance in breeding programs either towards hybrid maize production or synthetic varieties composed of hybrids which involved the good combiners for the traits in view.

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