Winter wheat has the potential to produce 20 – 30% higher yields than spring wheat as the winter crop can more efficiently utilize spring moisture, out-compete weeds and due to early maturation, circumvent the peak of Fusarium Head blight infections.  However, due to insufficient winter-hardiness in current cultivars, Prairie producers’ are hesitant to cultivate winter crops due to harsh prairie winters.  The research objective was to elucidate the genetic mechanisms underlying winter hardiness and improve the winter field survival of fall seeded winter wheat. The practical aim was to develop germplasm with a few degrees lower LT₅₀ value than Norstar (released 1977) and a winter field survival equal to the hardy winter rye cultivars.

Acquisition of frost tolerance in fall-seeded winter cereals and their field survival during winter is a complex interaction between the Fr-A2 locus on chromosome 5A (CBF gene cluster) and developmental genes located at various locations on the genome. These interactions determine the start temperature of cold acclimation, cold acclimation rate and the length of the cold acclimation phase. Genetic mapping was used to characterize chromosomal regions associated with (i) increased low temperature tolerance; (ii) developmental traits and (iii) identifying recombinant inbred lines (RIL) combining these regions.  Every year, since 2014 field trials were conducted to assess winter field survival at the University of Saskatchewan, Kernen Research Farm, AAFC Lethbridge and Vauxhaul, Alberta. . Most of the informative data has been obtained from the Saskatoon trials, where good segregation for winter survival was obtained for the RIL population and rye genotypes in three out of five years of trials. The 2016/17 trial resulted in a good segregation for winter survival in the RIL population and 22 RILs with high winter survival. These scores were similar or higher than the best scores for the wheat control lines Norstar and a close relative, W304 (survival scores of 33.9% and 22.8%, respectively), but lower than the best rye lines (100 %). Whole plant freeze tests optimized in this project also identified 26 RILs with LT₅₀ lower than Norstar, which suggests that these RILS have improved low temperature tolerance than Norstar. A few of the promising RILs were also tested in replicated small plots during 2016/17 and three RILs in the plot tests confirmed to have winter survival at par with Norstar (58.3 %) or higher (75.8 %). The grain yield from two of these winter-hardy RILs were also similar to Norstar.  Preliminary observations indicate good survival to yield meaningful results. It is important to note that all field trials conducted in this project are done on tilled soil, which provides a much harsher winter condition than fields with stubble that are normally used for winter wheat production on the Prairies.

In conclusion, the main research objective to develop and characterize winter wheat lines that exceed the low temperature tolerance of the most cold-hardy winter wheat cultivar Norstar was achieved.  The characterized RILs are currently being used by the AAFC winter wheat breeding program to introduce the cold hardy genes into elite cultivars to increase their cold hardiness.  Winter wheat cultivars with improved cold-hardiness and winter field survival will encourage prairie farmers to adopt the most environmentally friendly winter wheat cultivars that more efficiently use spring moisture, reduce input costs and increased wheat yields.