This study examines the relationship between plant height, winterhardiness and genotype-by-environment interaction in the grain yield of winter wheat in western Canada. Positive correlations between plant height and winter survival ability (WSA) and between plant height and lodging score have persisted among entries in Western Hard Red Winter Wheat Cooperative Trials (WWC) for 33 yr. Progress has been made in developing winterhardy semidwarfs; however, no short cultivars have yet been isolated in the most hardy group. For Saskatchewan and Manitoba trials, correlations between WSA and yield (WSA:Y) were mostly positive, indicating widespread and intense cold stress. In southwest Alberta trials, WSA:Y ranged from significantly positive to significantly negative, indicating the wide range and unpredictability of cold stress in this area; in North and Central Alberta the distribution of WSA: Y was intermediate between southwest Alberta and Manitoba and Saskatchewan. In high stress trials (WSA:Y > 0.4), cultivar grain yield increased with increased cultivar height (on average, +0.024 tonnes ha−1 for each centimetre increase in height) but as stress levels declined, this relationship was reversed. In trials with WSA: Y < −0.4, cultivar yield was negatively related to cultivar height (average slope of −0.026 tonnes ha−1 per centimetre increase in height). Similar results were found in a trial of six winter wheat cultivars over three sites and 6 years within southern Alberta. In high stress trials, tall and hardy cultivars stabilized grain yield through high rates of survival while non-hardy cultivars performed poorly. Without damaging cold stress, short and non-hardy cultivars showed the highest yields and the greatest response to environmental productivity. Key words: Yield, winterhardiness, coldstress
Protein Changes in Roots of Winter Wheat Subjected to a Cold Stress