GENETIC STUDIES ON GRAIN YIELD AND ITS COMPONENTS IN TWO BREAD WHEAT CROSSES

This research was carried out at the Experimental Farm of Sakha Agricultural Research Station, Kafr El- Sheikh, Egypt, during the three growing seasons of 2013 / 1 4, 2014 / 1 5 and 2015 / 1 6 to estimate genetic variance components and type of gene action controlling the inheritance of yield and its component characters, using six- population model. Genetic materials used in this study included six populations (P1 , P2 , F1 , F2 , BC1 and BC2 ) of the two bread wheat crosses (Sakha 95 X Giza171) and (Sakha 95 X Line 1). Results revealed that, the mean effects (m) were highly significant for all characters in both crosses, indicating that these characters are quantitatively inherited. Also, the relative importance of additive and dominance effects varied with characters and crosses. The most predominant type of epistasis was additive X dominance (ad) and dominance X dominance (dd) in most characters, proving that these characters were greatly affected by these types of gene action. Broad - sense heritability values were high for all studied characters in both crosses, while narrow sense heritability, their values were ranged from low to moderate for the two crosses. Based on the obtained results, both crosses could be useful in the breeding progra m to develop promising lines. However, heritability and expected genetic advance from selection were higher in magnitude in the first cross (Shaka 95 X Giza 171), indicating that this cross could be more useful in isolating new promising lines and hence development of new cultivar(s) having high yielding ability.