Hormonal regulation of preharvest sprouting in wheat

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The production of wheat, one of the major economically important crops of Canada, is hampered by a variety of stress factors, including wet conditions prior to harvest that cause grains to germinate while still on the spike, termed as preharvest sprouting (PHS). PHS causes loss in grain yield and quality, incurring a high cost for wheat producers. The degree of grain tolerance to PHS is regulated mainly by the balance between abscisic acid (ABA) and gibberellins (GA), which are among the plant produced compounds that influence growth and developmental processes at very low concentrations, usually coined as "plant hormones". ABA promotes PHS tolerance whereas GA enhances germination, and the ratio between these two hormones is modulated by changes in their respective production and degradation processes. Seeds with a low ABA to GA ratio exhibit increased potential for PHS. By contrast, a high ABA to GA ratio in seeds leads to increased PHS tolerance. Several strategies and regulatory elements involved in the modulation of the balance between the levels of ABA and GA have been identified in other plant species. However, very little is known about how the two hormones coexist and interact in regulating the tolerance of wheat grains to PHS. The goal of this research is to identify specific elements that regulate ABA production in wheat, and investigate their role in controlling the levels of GA and PHS tolerance in the grains. The findings of this research will provide powerful tools to develop wheat cultivars with adequate PHS tolerance; thereby improving wheat yield and quality, and farm income for Canadian wheat producers. Further, this research involves the training of highly qualified personnel in the area of crop biotechnology, which is critical to the competitiveness of Canada's crop industry.