Study on physiological responses and adaptation of some grapevine cultivars against sever heat stress condition in south of Fars province

In recent years grape growing has been extended to warm climate regions in Fars province. In other hand, heat stress is considered as major factor which affected yield and quality of grape production in these regions. The aim of this study was to determine heat tolerance ability in four three-year-old grapevine cultivars (̒Rotabi̕, ̒Askari̕, ̒Monagh̕ and ̒Flame Seedless̕) against sever heat stress under vineyard condition. This research was carried out in Ghir-O-Karzin region of Fars province for two years. The experimental design was a randomized complete block design with four replicates and three vines in each plot. Leaf chlorophyll content, relative water content (RWC), electrolyte leakage (EL), and leaf gas exchange parameters were measured. The results showed a significantly differences in El, E, gs, A/Ci, photosynthetic rate (A) and leaf temperature. No significantly differences were observed for other parameters. Heat stress increased substomatal CO2 concentration with equal amounts in all cultivars. But heat stress decreased stomatal conductance (gs) and Photosynthetic rate (A) in all cultivars. Flame Seedless had a relatively desirable photosynthetic rate and was a heat-tolerant cultivar. Photosynthetic rate of ̒Rotabi̕ was less than ̒Flame Seedless̕. Therefore, it was a moderately-heat-tolerant cultivar. ̒Askari̕ and ̒Monagha̕ were heat-sensitive cultivars compared to ̒Flame Seedless̕ and ̒Rotabi̕.