Assessment of genetic diversity for terminal heat tolerance in bread wheat (Triticum aestivum L. em. Thell.)

Abstract

Heat stress in wheat bears very high significance in realsing yield potential of a genotype. Terminal heat stress in particular affects the wheat yields considerably. Keeping this in view the present investigation was carried out with 32 diverse genotypes of bread wheat in completely randomized block design with 3 replications at G.B. Pant University of agriculture & Technology, Pantnagar for studying the genetic diversity for terminal heat stress tolerance under late sown condition. The observations were recorded on 16 agronomic traits and 3 physiological traits. The statistical analysis for genetic divergence was done using Mahalanobis-D2 statistics and clustering of genotypes was done using Tocher method. On the basis of genetic diversity analysis, it was found that the maximum percent contribution towards genetic divergence was from grain yield/plot i.e. 47.98% and minimum by the harvest index (0.81%). Clustering of genotypes revealed that cluster- I and III have maximum number of genotypes (14) and clusters-II, IV, V & VI each has single genotype only. The highest intra-cluster distance was exhibited by cluster-III (703.41) revealing maximum genetic divergence among its constituents. The highest inter-cluster distance was found between clusters-V and VI (7190.38). The nineteen genotypes were found tolerant. The genotypes bearing desired values from different clusters can be exploited in future breeding programme for improving the yield and physiological traits under late sown condition for mitigating the threat of terminal heat stress in bread wheat.