Evaluation of sesame cultivars germination on response to temperature: determination of cardinal temperatures and thermal tolerance

The aim of this study was to evaluate germination of different sesame genotypes on response to temperature. Heat and Cold Tolerance Indexes were determined using cardinal temperatures and evaluations of genotypes were conducted to tolerate high or low temperatures using determined indexes. In order to, germination tests were conducted in fixed temperatures incubators with 10, 15, 20, 25, 30, 35, 40, and 45 oC on 9 sesame genotypes, in 4 replications with 50 seeds. Finally, cardinal temperatures were estimated using segmented function, and tolerant genotypes to high or low temperatures were determined using estimated cardinal temperatures. Results indicated that mean of base (Tb), optimum (To) and ceiling (Tc) temperatures were 12. 8, 38. 0 and 49. 3oC for studied genotypes. Thermal tolerances in sub-optimal, supra-optimal and total thermal tolerance were 25. 2, 11. 3, and 36. 5 oC, respectively. Tolerance index to cold or heat were significantly differed among genotypes, and the mean of them were 2. 37 and 2. 73. Finally, maximum germination rate, heat tolerance index (HTI) and Tb had the maximum heritability ratio with 98. 3, 95. 9 and 95. 5 ٪ and the minimum heritability ratio was 3. 2 ٪ for Tc.