Genetics of yield determining factors in spring wheat over environments

Genetics of yield determining factors was studied in a set of 10 X 10 half-diallel progenies (F₁ and F₂) of springwheat over three environments. The results of components of variance analysis pooled over environments revealed that both additive (D) and nonadditive (H₁ and H₂)components of variation were involved in the expression of almost all the characters in F₁ as well as F₂ generations. However, the nonadditive components were higher than additive component excegt in few cases in F₁ where the additive component was preponderant. The {H₁/D)^1/2 values revealed overdominance for all the characters in both generations except for days to heading, plant height, peduncle length, spike length and spikelets per spike in F₁, where partial dominance was recorded. The values of Fexhibited excess of dominant alleles for days to heading, days to maturity, spikelets per spike (F₁ and F₂) and peduncle length (F₂), and directional dominance of the decreasing genes for plant height and spike length (F₂. Biparentalmating and/ordiallel selective mating system could be the best breeding method for more tangible advancement in spring wheat.