Evaluation of Terminal Heat Stress Tolerance in Some Bitter Vetch Ecotypes

Terminal heat stress as one of the major abiotic stresses has an important role in reducing growth and crop production in many areas of the world including central and southern Iran.

To evaluate the effect of terminal heat stress on grain yield and some its related traits in bitter vetch, a field experiment was conducted in a randomized complete block design with three replications on 18 bitter vetch ecotypes from four provinces (East Azerbaijan, West Azerbaijan, Ardabil and Zanjan) in the Research Field of Faculty of Agriculture at Vali-e-Asr University of Rafsanjan, Iran in 2020-2021 cropping seasons. The ecotypes planted in three sowing dates (13 Feb., 28 Feb. and 15 Mar.) and the data were combined and run in a combined analysis of variance. The sowing dates were considered the plant will end with the heat of season. Days to 50% flowering, days to flowering end, days to maturing end, plant height, root length, biomass, grain yield, thousand kernel weight and harvest index were measured.

The results of combined analysis of variance showed there were significant differences among the studied ecotypes for all traits in their reaction to terminal heat stress that were implicated high genetic diversity among ecotypes. According to the results of mean comparison of the evaluated traits, terminal heat stress (induced by delay in differnrt sowing dates) caused significant reduction in all traits except plant height and root length. Aso, the results showed that the interaction of sowing date and ecotypes had significant effects on the most of traits. Cluster analysis based on the measured traits at different sowing dates (13 Feb., 28 Feb. and 15 Mar.), was done and the studied bitter vetch ecotypes were divided into 3 groups in each sowing date.

Regarding to the results, Maragheh and Bayghout ecotypes both from East Azerbaijan in terms of tolerance to terminal heat stress were superior to other ecotypes and recommended for direct planting in Rafsanjan condition or using in breeding programs for terminal heat stress.