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Six diverse wheat cultivars (Triticum aestivum L.) were used in a partial-diallel crosses to produce 15 F1, hybrids. Genetical analysis and heritability, was estimated for days to heading, days to maturity, grain filling period, plant height, spike length, number of spikes /plant, 1000-grain weight, number of kernels per spike, grain yield/ plant and grain protein content. Mather and Jinks (1971) and Hayman(1954 a and b) methods were used to estimate the genetic parameters for studied characters. Significant mean squares were obtained for genotypes, parents and crosses for all traits studied under the three nitrogen levels. Thus, the parental cultivars displayed enough of genetic variability. The significant of mean squares for parents vs. crosses provide evidence for heterosis. Moreover, nitrogen mean squares were significant indicating that these characters behaved differently from one nitrogen level to another. The local wheat cultivar Shandaweel1 (P3) was superior for giving higher number of grains/spike, 1000-grain weight and grain protein content % while Gemmeiza9(P4) was the best for giving more number of spikes/plant and grain yield. Meanwhile the cross combination (Shandaweel1×Gemmeiza9 gave the heaviest 1000-grain weight ant the maximum value of number of grains/spike and grain yield /plant was obtained by the cross (P1×P5). These results hold true under the three nitrogen levels. The additive genetic variances (D) were significant for most of studied traits under three nitrogen fertilization levels. Significant values for the dominance components (H1) were obtained for all traits under three nitrogen fertilizer levels. Values of (H1) were larger in magnitude than their respective (D) ones for all traits under three nitrogen levels. Values of H2 were found to be smaller than H1 for all traits under the three nitrogen levels. Studies on degree of dominance revealed the presence of over dominance for days to maturity, grain filling period, plant height, spike length, number of grains per spike, grain yield per plant and grain protein content at the three nitrogen level. The average degree of dominance (H1/D) 1/2 were found to be nearly equal unity for days to heading and 1000 grain weight at low nitrogen fertilization indicating that these characters were controlled by compelet dominance. The proportion of genes with positive and negative effects in the parents as indicated by H2/4H1 were lese than its maximum value (0.25) at the three nitrogen fertilization levels for days to heading, grain filling period, plant height, number of spikes/plant and grain protein content% suggesting asymmetrical distribution of positive and negative alleles among the parental population. While, it was near to its maximum value (0.25) for 1000-grain weight and grain yield/plant at low and medium N fertilization levels, days to maturity and number of grains/spike at 75kg.N./fad. indicating equal distribution of positive and negative alleles. Estimates of the ratio of dominant to recessive alleles in the parents KD/KR were mor...

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