1 Can ABA signaling be used to develop drought tolerant wheat?

Wheat yield and quality can be compromised by drought stress and preharvest sprouting (PHS) on the mother plant. It is believed that problems with PHS are due to lack of grain dormancy partly resulting from lack of ABA sensitivity. The long term goal is to use wheat mutants with increased sensitivity to ABA to increase grain dormancy and drought tolerance. ABA is required to set up grain dormancy and embryo desiccation tolerance during embryo maturation, and stimulate storage of nutrients. ABA also inhibits germination of mature seeds and stimulates stomatal closure in response to drought stress. A screen for wheat mutants with altered response to ABA in seed germination has been used as a first step to isolate wheat plants with increased ABA sensitivity. Mutants have been characterized for changes in ABA dose-response. In addition, ABA hypersensitive grain germination appears to correspond to reduced vegetative transpiration under drought stress and decreased carbon isotope discrimination