| A field experiment was conducted in Dhi-Qar Governorate during winter season 2015-2016 to study genetic and phenotypic variation and genetic, phenotypic and environmental correlations, broad sense heritability and path coefficient for nine traits: plant height (PH), flag leaf area (FLA), tiller number (TN), spike number (SN), spike length (SL), grain number in spike (GN/S), 1000 grain weight (GW), biological weight (BW), grain yield (GY) in three wheat varieties: Aab’a99, Barcelona and Boro. The results showed that the values of phenotypic variance coefficient were close to those of genotypic variance coefficient for most traits: PH, TN, SN, GW, FLA, BW and GY. Thus the genotype can be studied through phenotypic data, and such traits can be considered as selection criteria in wheat breeding. The highest ratios of broad sense heritability were for PH, TN, FLA, BW and GY (0.83, 0.8, o.87, 0.86, 0.82 and0.95) respectively. Phenotypic correlation coefficients of all studied traits were positive and significant and generally were lower than genetic correlation coefficients. This indicates that variations among varieties were largely of genetic origin despite the existence of low environmental effect. Genetic correlations of GY in SN and GN/S traits were positive and the highest (0.941, 0.902) respectively. The highest direct effects on grain yield were of SN and FLA (1.283, 0.993) respectively. Therefore, Path coefficient analysis reveals that the direct selection of these two traits will be helpful in breeding programs for improving grain yield in wheat crop. |