The Acquisition and Maintenance of Thermotolerance in Australian Wheats

Abstract

The exposure of wheat (Triticum aestivum) coleoptiles to a transient high temperature stress results in the synthesis of a group of proteins known as the heat shock proteins (hsps). The appearance of these proteins is associated with a concomitant reduction in normal protein synthesis and has been correlated with the acquisition of thermotolerance (assessed as growth of coleoptiles). Pretreatment with a sublethal heat shock confers protection to a subsequent heat shock that would otherwise have been lethal. In addition, we find that increasing the time interval between the sublethal heat treatment and the subsequent heat shock from 0 to 72 h reduces the protective effect of the sublethal heat treatment considerably. The five cultivars examined (Sunelg, Sunco, Hartog, Vulcan, Halberd) showed differences in the degree of protection acquired, and in the length of time for which protection was maintained. Hartog was found to be the most thermotolerant, and acquired the greatest degree of protection from exposure to a sublethal heat treatment, but the duration of this acquired protection was shorter than in the remaining cultivars. Sunelg was most susceptible to a heat shock but the duration of acquired protection was the greatest.