Sami Sheikhmous Othman

General Commission for Scientific Agricultural Research-Department of Agronomy
Fac. of Agric.- Ain Shams Univ.
2013.

ABSTRACT

This investigation was conducted at Agric. Res. Station Farm, Faculty of Agric., Ain Shams Univ. at Shalakan, Kalubia Governorate during the three successive growing seasons of 2009/2010, 2010/2011 and 2011/2012. The objective was to estimate some genetic parameters for grain yield and yield related traits, in order to enable the breeder to choose the suitable breeding procedure for developing new improved wheat genotypes using the six populations, i.e., P1, P2, F1, F2, BC1 and BC2 of three bread wheat ( Triticum aestivum, L. ) crosses, viz. Giza168 x Cham8 (cross I), Giza168 x Bohouth6 (crossII) and Sakha94 x Bohouth6 (cross III).
Results of analysis of variance indicated significant differences among the studied generations of each cross for all studied traits. The genetic variances within F2 population were also found to be significant for all traits studied in the three crosses. The three studied crosses exhibited significant positive heterosis percentages over the mid and better parent values for most of the traits under study, except days to heading and days to maturity which exhibited significant negative (desirable) heterosis values in the three crosses with few exceptions. Significant positive and negative inbreeding depressing percentages were detected. Over or complete dominance of the higher parent was observed for different traits in the three crosses, except absent dominance was found for days to heading and no. of spikes/plant in cross III.
The scaling test values of A, B, C and D were found to be significant for different studied traits, except few cases, suggesting the
presence of non-allelic interaction. F2 deviation (E1) and backcross deviation (E2) were also significant, with few exceptions, retiring the contribution of epistatic gene action in the inheritance of the studied traits. The six parameters model showed that the additive x additive (aa) type of epistatic gene action, followed by the dominance gene effects (d) and the additive gene effects (a) contributed by the large part of the genetic components controlling the inheritance of the studied traits compared to the additive x dominance (ad) and dominance x dominance (dd) types of epistatic gene effects. Moderate to high heritability estimates in the broad sense and relatively low to high heritability estimates in the narrow sense were obtained for most of the studied traits. The expected genetic advance from selection in the F2 population for the studied characters was found to be moderate to high. Results of path coefficient analysis revealed that no. of spikes/plant, no. of kernels/ spike and 100-kernel weight proved to be the major grain yield contributors.
The RAPD -PCR analysis indicated that the primers OP-A18, OP-AX16 and OP-C04 could be used as markers assistant selection for early heading segregates in the F2 generation, while the primer OP-F04 could be used as marker assistant selection for late heading segregates in the same generation.
In general, results showed that crosses I and II may be utilize in wheat breeding programs as promising materials for producing F1 hybrids and/or developing lines characterized by earliness in maturity with high grain yield/plant in bread wheat breeding programs.
Key Words: Bread wheat, Heterosis, Inbreeding depression, Potence ratio , Gene action, Heritability, Genetic advance, Correlation, Path coefficient and RAPD – PCR.