Effect of Heat Treatment on Physiological and Recovery Growth Status of Two Tomato Cultivars With Different Heat Susceptibility

Abstract

High temperature seriously effects on plant vegetative and reproductive development and reduces productivity of plants, while to increase crop yield is the main target in most crop heat stress tolerance improvement breeding programs, not just survival, under high temperature. Our aim was to compare temperature stress tolerance in two commercial tomato cultivars “Dafnis” (big fruit size) and “Minichal” (cherry fruit size) to develop early screening methods and find out survival rate and physiological responses of tomato cultivars on high temperature (40°C and within 70% RH, day/night) in 4-5 true leaf seedling stage- (4LS) and identifies the linkage of heat tolerance with fruit set and leaf heat damage rates (LHD) in seedling stage with subsequent vegetative traits at recovery. Results showed that heat stress significantly affected on physiological-chemical and vegetative parameters of seedlings regardless of tomato cultivars. Survival and the threshold level of high temperature tolerance in the seedlings of cv. “Dafnis” and “Minichal” were identified on days 7 and 9, respectively. Our findings revealed that photosynthesis (PN, Gs, Ci, Tr) parameters were increased and CHL content persisted steady value in cv. “Minichal” during heat stress period, however EC and RPL rates were lower than cv. “Dafnis”. Heat stress reduced the SFW in both cultivars in seedling stage, but PH and RFW were significantly decreased in the heat tolerant cv. “Minichal”, whereas this parameters were not significantly ranged in the heat susceptible cv. “Dafnis”. Additionally, there no found linkage between vegetative parameters with decreasing of PN and CHL rates during HT of seedlings. In plants of cv. “Minichal” with LHD-25, 50 and 75% were no found significant differences in PH, whereas in cv. “Dafnis” significant differences were determined in plants with LHD-75%, and the significant differences in rates of SFW and RFW were observed in plants of cv. “Dafnis” having LHD-75% for 28 days of recovery at NT condition. Taken together, we concluded that heat stress affected on physiological parameters regardless of tolerance level, and to identify heat tolerant genotype in tomato breeding program, screening and selection genotypes have to be evaluated at the vegetative and reproductive stages with consideration fruit size types. Since we could not find linkage between heat tolerances in seedling stage with fruit set at the reproductive stage and fruit set cannot be used as a general predictor of heat tolerance.