Nine new developed inbred lines of maize were crossed in a diallel cross system to estimate the combining ability for nine characters under two different planting dates. Results indicated that planting dates mean squares were significant for all of the studied traits except for plant height, ear height and 100-kernel weight Crosses mean squares were highly significant for all characters in the the two planting dates and their combined analysis. Highly
significant variance for general (g.c.a.) and specific (s.c.a.) combining ability were detected for all of the studied traits, High ratios of g.s.a./s.c.a. mean squares were obtained for all traits indicating the predominance of additive and additive x additive gene actions in the inheritance of the studied traits. Significant interaction between both types of combining ability and planting dates were detected for silking date, ear height, ear length, number of rows/ear, and grain yield/plant. The parental line Moshtohor 26 (M26) was the best combiner for silking date. Line M24 seemed to be the best combiner for plant height. Car height and number of rows/ear Also, line M13 was the best combiner for grain yield per plant and most of its components The most desirable sca. Effects were obtained in the crosses (M32 x M99) for silking date and plant height. (M13 x M24) for ear length. Number of grains/row and grain yield per plant. (Ml2 x M26) for ear dianictcr. (M13 x M32) for number of rows/ear and (M12 xM32) for 100-kernel weight The highest iiicrcases in grain yield/plant relative lo Giza-2 and T W.C 310 were obtained for the cross (M8 x M46). Being 17 59% and 26 79%. respectively followed by the cross (Ml3 x M24).
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