Assessment and role of genetic diversity of component traits for improving grain yield and heat tolerance in bread wheat (Triticum aestivum)

The present investigation was carried out in a randomized block design (RBD) with 20 diverse wheat (Triticum aestivum L.) genotypes grown under three environments i.e. 25th November, 2012 (Environment-I, timely sown), 24th December, 2012 (Environment-II, late sown) and 15th January 2013 (Environment-III, very late sown). The environment wise analysis of variance for grain yield and its contributing traits indicated highly significant differences among the genotypes for all the traits under study. High heritability along with high genetic advance and high coefficient of variation (PCV and GCV) for grain yield across three environments indicated substantial contribution of additive gene action in the expression of desirable traits and thus selection would be effective for genetic improvement of grain yield in wheat. On the basis of multivariate analysis, 20 genotypes were grouped into five clusters based on D2 value. The cluster V contained the maximum number of genotypes (6) in Environment-I,whereas cluster II included six genotypes in Environment-II, cluster IV included 07 genotypes in Environment-III and on pooled analysis basis cluster V had 07 genotypes. The highest inter cluster values were observed between cluster II and III (2690.75), followed by cluster I and II (2494.51), cluster II and V (1334.53), cluster III and V (730.74) in the first, second, third environments as well as pooled analysis basis, respectively, and thus genotypes included in these clusters showed wide genetic diversity and thus may be utilized in hybridization programme targeting wheat breeding for obtaining transgressive segregants to improve grain yield under varying environments. Based on the cluster mean analysis, genotype K 512 in E-I (timely sown) and E-II (late sown) while AAI 13 in E-II (late sown), E-III (vary late sown) and also in pooled analysis were rated better performing for multiple yield traits and these genotypes can be considered in breeding programme as well as for further study for developing superior wheat genotypes.