Commercial inbred lines as testers for combining ability in new developed maize lines [electronic resource].

Includes references.

Eighteen selected S₃ yellow maize lines developed from different heterotic groups (Pop 45 Ev-4, DTP-2-C₅, Astrong H.D., AS-785, Bonner H.D. and PA V9 F₂)were topcrossed to each of two commercial yellow inbred testers, i.e. Gm 1004 and Gm 1021 in 2004 summer season. The resultant 36 topcrosses were evaluated in 2005 growing season at Gemmeiza, Sids and Nubaria Agric. Res. Stns for grain yield, number of ears/100 plants, days to 50% silking, plant and ear height. Testers contributed much more than the lines to the total genetic variation and were more affected by the environmental conditions. The inbred testers ranked the 18 inbreds differently. The tested lines L·7, L-9, L-10, L-14, L·15 and L-16 were found to be the best general combiners for high yielding ability. Potential females, L·1, L·4, L-5, L.7, L-8 and L·9 were significantly better general combiners for earliness. Parental lines L·1 and L·15 were good donors for prolificacy. The inbred tester Gm 1021 manifested better general combining ability GCA effects and higher average performance of grain yield as compared to testcrosses of the other inbred tester Gm 1004. Results showed that the inbred tester Gm 1021 crossed to the tested lines L-1, L-4, L-7< L-9< L-14, L·15 and L·16 would produce the best single crosses which _significantly outyielded the check single cross hybrid Pioneer 3084 with an average increase from 2.23 to 5.78 ardlfad. FUrlhennore, the--most outstanding crosses, i.e. L·7 x Gm 1021, L·16 x Gm 1021 and L-9 x Gm 1021 (32.98, 32.28 and 31.78 ardlfad), respectively significantly outyielded the best commercial yellow check hybrid SC 155 (29.10 ardlfad) by 3.88,3.18 and 2.68 ardlfad, respectively. The magnitude of the ratio of general to specific combining ability variances (o²sca / o²sca) that the additive component of gene action had the major role in detennining the inheritance of all studied traits. The non additive gene action, however, interacted more with the environmental conditions (²scs x location) than the additive component (o²gca x locations) for grain yield and number of ears/plant.

Summary in Arabic.

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