Use of Graphical and Numerical Approaches for Diallel Analysis of Grain Yield and Its Attributes in Bread Wheat (Triticum aestivum L.) under Varying Environmental Conditions

Improving yield is the main aim of plant breeders. In the case of bread wheat (Triticum aestivum), a major challenge in this regard is genotype-environment interactions, and a knowledge of these is required to successfully select high-yielding genotypes. In this study, graphical and numerical approaches of diallel analysis have been used to reveal such interactions. Ten different wheat genotypes were crossed using a half-diallel approach. The parents, hybrids, and standard checks were evaluated at the Regional Research Station, Anand Agricultural University, Gujarat, Anand, India under both standard and late-sown conditions in two separate years (E-1 and E-2 (normal-18 November 2018 and late sown-10 December 2018, respectively, Rabi 2018-2019), E-3 and E-4 (normal-18 November 2019 and late sown-10 December 2019, respectively, Rabi 2019-2020)). For each sowing, 't(2)' values were calculated for eleven phenotypic characteristics: days to 50% heading, days to maturity, plant height, number of effective tillers per plant, length of main stem, number of spikelets per main spike, number of grains per main spike, grain yield per main spike, grain yield per plant, 1000-grain weight, and harvest index. Components of the gene effect revealed that the number of spikelets per main spike in E-2 and E-4, and the number of grains per main spike in E-2 were governed by both additive and dominance gene action across the environments. Other characteristics were the greater influence of the dominance gene effect, except for days to 50% heading in E-1, E-2, E-3, and E-4; days to maturity in E-2, E-3, and E-4; grain yield per main spike in E-4. Many characteristics exhibited overdominance, an asymmetrical distribution of positive-negative, dominance-recessive genes, and narrow-sense heritability in all environments. In graphical analysis, regression value 'b' was unity for days to 50% heading (E-1 and E-4) and 1000-grain weight (E-3 and E-4), which revealed an absence of digenic interactions for these characteristics in the respective environments. Therefore, a given population may be improved to isolate superior recombinants for the development of desired parents in future breeding programs.