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Abstract
This investigation aimed to study heterotic effect,inbreeding depression, potance ratio,mode of gene action, heritability values, genetic advance and phenotypic correlation. br The materials used in this investigation comprised three parental bread wheat varieties two of which are local (Giza168 and Sids1) and the third is introduced (IB18). br The three varidies were crossed to produce two crosses. Parents, F1, BC1, BC2 and F2 of each cross were evaluated in 2006-2007 season for the following eight traits: days to heading, plant height, no. of spikes/plant, spike length, no. of spikelets/spike, no. of kernels/spike, 100-kernel weight and grain yield/plant. Results revealed that mean squares due to populations were highly significant for most studied characters in the two crosses, indicating that the six populations of each cross differed significantly for studied traits. Heterosis values were positive and significant relative to either mid parent or better-parent values in the two crosses for most of the studied characters,-#119;-#104;-#101;-#114;-#101;as heterosis values were negative and significant for days to heading in both crosses. Positive and significant inbreeding depression values were recorded for spike length in both crosses and for spikelets per spike in Cross І, -#119;-#104;-#101;-#114;-#101;as negative significant values were obtained for days to heading in Cross 1 and 100-kernel weight in Cross П. Over and complete dominance was recorded for all the studied characters except kernels/spike in Cross І as well as plant height and grain yield/plant in Cross П. br Scaling tests (A, B, C and D)indicated the presence of non-allelic gene interactions for all studied traits in both crosses. Additive genetic variance was significant for each of days to heading, spikes/plant,grain yield/plant and spike length in both crosses as well as kernels/spike in Cross П and for plant height and 100-kernel weight in Cross І. Dominance variance was significant for each of days to heading,plant height, spikes/plant, kernels/spike and spikelets/spike in both crosses. Epistasis effects were significant for most studied traits in the two crosses. br Broad sense heritability estimates were relatively high and ranged -#102;-#114;-#111;-#109; 77% to 93.83% in Cross І compared with values -#102;-#114;-#111;-#109; 52.8% to about 93% in Cross 2. Narrow sense heritability percentages ranged -#102;-#114;-#111;-#109; 41.38 to 81.59 in Cross І and -#102;-#114;-#111;-#109; 41.25% to 77.58% in Cross П for the studied traits. br The expected genetic advance as a percentage of the F2 generation mean (Δg%) was high for most of the studied traits, ranging -#102;-#114;-#111;-#109; about 9.80% of the F2 population mean for spike length to about 47.17% for number of kernels/spike in Cross I. Meantime, genetic gain percentages of about 5.58% for days to heading to about 52.56% for grain yield /plant were expected in Cross П. br Grain yield/plant was positively and significantly correlated at the phenotypic level with each of no. of spikes/plant and spike length in both crosses as well as with no. of spikelets/spike and 100-kernel weight Cross I and with no. of kernels/ spike in Cross П.