Inheritance of important traits in bread wheat over different planting dates using diallel analysis

This experiment was conducted to study the inheritance pattern of yield and its related traits in eight bread wheat (Triticum aestivum L.) cultivars and their 56 F1s hybrids over three planting dates (early, normal and late) at the Experimental Farm of NWFP Agricultural University, Peshawar, Pakistan during 2002-04. The experiment was planted in randomized complete block design in three replicates. Data were collected on flag leaf area, plant height, spike length, grain yield and harvest index. The F-test declared significantly different means for all traits justifying diallel analyses. Genetic analyses for all traits were carried out. The adequacy model test revealed that additive-dominance model was appropriate for plant height, spike length and harvest index over all environments; grain yield per plant under normal planting and flag leaf area under late planting. Analyses of genetic components (Hayman, 1954b) indicated significant additive (D) and dominant (H) genetic variations for plant height, spike length and harvest index under early planting. Under normal planting, significant additive (D) and dominant (H) genetic components were observed for plant height, spike length and grain yield per plant, while under late planting significant additive and dominance variations were found for flag leaf area and harvest index. Genetic analyses of traits confirmed the involvement of both additive and non-additive gene effects in governing the inheritance of these traits. Narrow sense heritability estimates were 69.74% and 82.15% for flag leaf area and plant height respectively, suggesting improvement through early generation selection, while the low narrow sense heritability estimates for spike length, grain yield per plant and harvest index favored selection at later stage.