The Impact Of Global Climate Change On The Freezing Tolerance Of Winter Cereals In Western Canada

Due to global climate change in Western Canada, winter cereals will be exposed to a higher frequency of winter thaws which will increase crown water and thereby reduce freezing tolerance. Cold-acclimated winter wheat (Triticum aestivumL.) and fall rye (Secale cerealeL.) were held at -4 degrees C under a snow cover for up to 120 days and periodically subjected to a dry or wet thaw for 3 days. Freezing tolerance was monitored by either the conventional freezing test (LT50) or the durational freeze test (LD50). There was a gradual loss in LT(50)and LD(50)in crowns held at -4 degrees C, with the greatest loss after 120 days. The LT(50)test could only identify species differences in freezing tolerance whereas LD(50)identified cultivar-specific differences. Rehardened plants previously subjected to a 4 degrees C dry thaw regained an LT(50)comparable to non-thawed plants. Whereas plants exposed to a wet thaw could only partially reharden. The more freezing tolerant fall rye cultivars maintained a lower LT(50)under thawing and rehardening conditions as compared with winter wheat. A short winter thaw dramatically reduced crown freezing tolerance. The selection of superior germplasm to tolerate warming winter conditions is an important goal for future winter wheat breeding efforts.