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EVALUATION OF ACQUIRED THERMOTOLERANCE IN WHEAT (TRITICUM AESTIVUM AND T. DURUM) CULTIVARS GROWN IN TURKEY

MUSTAFA YILDIZ^* AND HAKAN TERZİ

Abstract: Genotypic variability in acquired thermotolerance (ATT) among 30 cultivars of bread (Triticum aestivum L.) and durum (Triticum durum Desf.) wheat was evaluated at the seedling stage of growth by 2,3,5­triphenyltetrazolium chloride (TTC) cell viability and chlorophyll (Chl a+b) accumulation assays. In TTC assay, first leaf segments were subjected to heat stress (50°C, 1 h) after acclimation (37°C, 24 h) of 5­day old seedlings. In Chl accumulation assay, 5­day old etiolated seedlings were exposed to 25°C (24 h), 37°C (24 h) or 37°C (24 h)®50°C (1 h) treatments in dark. Etiolated seedlings were returned to optimum temperature at continuous light for Chl accumulation. Genotypic differences existed among cultivars tested for TTC at the seedling growth stage. Average acquired thermotolerance (ATT) value of all cultivars was 30.86%. Heat stress applied before greening of etiolated seedlings decreased Chl accumulation. High temperature treatments caused generally less injury to Chl pigmentation of bread wheat cultivars compared to durum wheat cultivars. Based on Chl accumulation, average ATT of all cultivars was 48.40% in 37°C®50°C/25°C ratio. Compared to Chl, carotenoid accumulation was less sensitive to direct high temperature treatment (50°C, 1 h) after acclimation treatment. The decrease in chlorophyll/carotenoid ratio of bread wheat cultivars was lower than that of durum wheat cultivars. Following the post­heat stress, the carotenoid content of bread wheat cultivars was lower than that of durum wheat cultivars and thus the decrease in chlorophyll/carotenoid ratio was found at low level. TTC and Chl accumulation tests were found to be appropriate for monitoring high temperature stress.

Afyon Kocatepe University, Faculty of Science and Arts, Department of Biology, 03200 Afyonkarahisar, Turkey. ^*E­mail: mustafa_yildizus@yahoo.com