Genetic estimation of grain yield and its attributes in three wheat (Triticum aestivum L.) crosses using six parameter model

Grain yield is a complex polygenic trait representing a multiplicative end product of contributing yield attributes governed by simple to complex gene interactions. Deciphering the genetics and inheritance of traits/genes influencing yield is a prerequisite to harness the yield potential in any crop species. The objective of the present investigation was to estimate genetic variance components and type of gene action controlling yield and its component traits using six populations (P₁, P₂, F₁, F₂, BC₁ and BC₂) of the three bread wheat crosses. Cross I (25th HRWSN 2105 × WH 1080), cross II (22ndSAWYT323 × RSP 561) and cross III (22ndSAWYT333 × WH 1080) involving elite stripe rust resistant wheat genetic stocks in combination with commercial check varieties were used for analysis. A combination of morpho-physiological, biochemical and disease influencing traits were evaluated, thus exploring the possibility of multi-trait integration in future. Results revealed that the estimated mean effects (m) were highly significant for all the traits in all crosses, indicating that selected traits were quantitatively inherited. The estimate of dominant gene effect was highly significant for plant height, number of tillers per plant in all the three crosses. Grain yield per plant was highly significant in the cross II while total protein content was highly significant in both crosses II and III. Glycine betaine content showed significant additive genes effect. Duplicate epistasis was the most significant for traits like plant height, total protein content and grain yield per plant. Dominance gene effect was more important than additive gene effects in the inheritance of grain yield and most other traits studied. The magnitude of additive × additive gene effects was high and positively significant whereas dominance × dominance was negatively significant for most of the traits studied in the three crosses. Additive × dominance gene effects was of minor significance, thus indicating that selection for grain yield and its components should be delayed to later generations of breeding.