Estimation of Some Genetic Parameters through Generation Mean Analysis in Three Bread Wheat Crosses.

The present investigation was conducted in 2009/10, 2010/11 and 2011/12 wheat growing seasons at Sakha Agric. Res. Station, Egypt. The analysis of gene effects used the means of six populations: P1, P2, F1, F2, BC1, and BC2; of the three bread wheat crosses to estimate genetic parameters. These crosses were Giza 168 x Sids 13, Gemmeiza 9 × Misr 2 and Sids 12 × Misr 2 generated from five diverse parents. Means of the six generations were recorded for seven characters. i.e. number of days to heading, days to physiological maturity, plant height. number of spikes per plant. number of kernels per spike, 100-kernel weight and grain yield per plant. Analyzed data revealed that there were variations among parental genotypes for all studied characters in all crosses except for number of kernels per spike in the first cross. days to physiological maturity and plant height in the second cross and grain yield per plant in the third cross. The genetic variance among F2 plants was significant for all studied characters in the three crosses. Generation mean analysis using scaling test (A, B and C) indicated the presence of digenic epistasis for all studied characters in the three crosses except for kernel weight in the second cross. The additive, dominance and epistatic gene effects were important in controlling the inheritance of number of kernels per spike in the first cross, days to heading in the second cross and kernel weight in the third cross. Heterosis compared to mid-parent and better parent were found to be significantly positive for plant height in the first two crosses. number of spikes per plant in the second cross and grain yield per plant in the third one. The inbreeding depressions were highly significant and positive for all studied characters in the three crosses except for days to heading in the first cross. Heritability estimates in broad and narrow senses were generally moderate to high for most studied characters in the three crosses. Meanwhile, the values of heritability in narrow sense were low for number of kernels per spike, kernel weight and grain yield per plant in the cross Giza 168 x Sids 13. The expected genetic advance from selection estimates in the F2 were low for number of kernels per spike and kernel weight in the first cross. days to heading in the second cross and days to physiological maturity in the third one. Variance component estimates revealed that additive genetic variance (σ²D) was larger than dominance variance (σ²H) for all characters in most crosses. The average degree of dominance as indicated by (H1/D)1/2 was less than unity for days to heading, plant height and grain yield per plant in the second cross as well as for kernel weight in the third one. Also, it was less than unity for days to physiological maturity in the first and third crosses, number of kernels per spike in the last two crosses and number of spikes per plant in the three crosses indicating the presence of partial dominance. On the contrary, the same parameter was more than unity for plant height, number of kernels per spike. kernel weight and grain yield per plant in the first cross as well as grain yield in the third cross indicating the presence of over- dominance. Based on these results, the second cross: Geinmeiza 9 x Misr 2 could be selected for obtaining plants having high grain yield. Moreover, the first cross: Giza 168 Sids 13 is promising for selecting early mature plants. [ABSTRACT FROM AUTHOR]