Assessment of Genetic Variability and Direct-Indirect Contribution of Post-Anthesis Traits to the Grain Yield in Bread Wheat (Triticum aestivum) at Different Sowing Dates

In cotton-wheat cropping system of Pakistan, sowing of wheat is delayed which results in a heavy loss to the farmers. To this end, a two-year field experiment was conducted to i) asses the performance of genotypes under late sowing ii) heritability and genetic association of different traits under normal and late sowing for their use in the breeding programs. Experimental factors included 20 diverse wheat genotypes (16 advance lines and 04 approved varieties) factorially combined with two sowing dates i.e., normal sowing (11 and 13 November in 2018 and 2019, respectively) and late sowing (09 and 11 December in 2018 and 2019, respectively). The results revealed a highly significant (P < 0.01) effect of genotype and sowing date on all the post-anthesis studied traits and the interaction of the two factors was also significant (P < 0.01) for all the traits except number of spikelets per spike. Contribution of sowing dates was more in overall variation of different post-anthesis traits than genotypes and their interaction. With respect to the performance, genotype 9725 performed best in both early and late sowing, but a reduction of 26% in the grain yield was observed due to late sowing, whereas the grain yield of Miraj-2008 was comparatively lower but showed a reduction of only 17% due to late sowing. Number of tillers per plant and biological yield showed a highly significant (P < 0.01) correlation (r= 0.38 and 0.72, respectively) with grain yield under normal conditions, but path analyses revealed that number of tillers per plant showed association indirectly through biological yield and its direct effect is only one third of the total effect. Under late sowing, association of number of tillers turned non-significant and direct effect become negative which showed complicated association of this trait under normal and late sowing. High broad sense heritability (H2 > 75%) of all the traits suggests a good genetic gain in breeding program by using these traits. As different genotypes performed best for different yield related traits, therefore a breeding program with a careful crossing plan should be developed to pyramid the genes for different traits for the development of genotypes adapted to late sowing. © 2021 Friends Science Publishers