| Heritability : Heritability percentages for the DS derived populations from both M2 mutant types (SS and GH) are presented, for yield and yield component traits, in Table 5. The results showed that the values tended to be higher for the selected traits, i.e. grain yield (83.91%) and harvest index (78.79%). It can be concluded that the DS mutagen increased heritability values of both selected traits. KASSEM et al. (1976) found that heritability percentage for grain yield (82%) was much higher in EMS derived population of Sonora 64 wheat cultivar. This clearly suggests that the environment has a little influence, and the mutagen has induced a wider variability. Consequently, improvement through DS mutagenic treatment is possible in these particular traits because it generally causes point mutations rather than chromosomal aberrations (SHARMA & SEARS 1964, WASHINGTON & SEARS 1970). If the induced variability is due to point mutation, it should be heritable and useful in a hybridization program (KRULL & FREY 1961). Contradictory, the number of spikes per plant, number of kernels per spike and 100-kernel weight showed decreases in heritability with values of 35.96, 49.96 and 52.98% respectively for these traits. These results matches with those reported by KASSEM et al. (1976) in number of kernels per spike (54 to 60%) and kernel weight (38 to 46%). These results clearly shows that these traits selection might not be profitable in early generations, because of the higher environmental effect. Correlation Coefficient : Adequate knowledge of interrelationship between factors related to complex characters, such as grain yield, is essential for designing successful wheat breeding programs. Estimates of genotypic and phenotypic correlations between all possible combinations of five traits, i,e., grain yield per plant, number of spikes per plant, number of kernels per spike, 100-kernel weight and harvest index in M2 populations are presented in Table 6. In general, the genotypic and phenotypic correlation coefficient values matched closely in each case. Grain yield was significantly positive correlated with all traits. Apparently, it appeared that during selection for increasing grain yield in populations resulting after mutagenic treatment the other traits will increase directly at the same time. SIDDIGQUIet al. (1981) found that grain yield was positively correlated with the number of tillers per plant and number of grains per spike in mutants derived from C 591 and Nayab bread wheat. BHATT (1973) concluded that the direct effect of kernel weight on yield was quite high. Likewise, the other traits expressed strong positive correlations with each other. It could be said that the direct effect of selection on one trait in segregating populations from mutagenic treatment resulted in significant increases in other traits. |
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