1a. Objectives (from AD-416)
Agronomically important genes for wheat will be identified and deployed using a genetic approach in wheat and Arabidopsis. The genetic mechanisms by which the plant hormones abscisic acid (ABA) and gibberellin (GA) control pre-harvest sprouting, stand establishment, and drought and cold tolerance in wheat and Arabidopsis. Spring and winter wheat cultivars with durable resistance to stripe rust, soilborne disease, cold and drought, and improved end-use quality will be developed.
1b. Approach (from AD-416)
Multiple approaches will be employed. The genetic diversity of wheat plants will be increased using wide crosses to wheat relatives and thorough mutagenesis and selection of new traits. We will determine whether ABA sensitivity controls grain dormancy and tolerance to preharvest sprouting using wheat mutants with increased and decreased sensitivity to ABA. The degree to which preharvest sprouting, drought tolerance and cold tolerance depends upon ABA sensitivity will be determined using association mapping, and wheat mutants with increased and decreased ABA sensitivity. The mechanisms by which GA signaling controls seed dormancy and plant height using Arabidopsis as a model system to determine exactly how GA response genes control gene expression during seed germination. New sources of genes giving superior end-use quality, disease resistance, and resistance to cold and drought conditions will be identified through characterization of material from the USDA-ARS National Small Grains Germplasm Collection. New approaches for deployment of these genes through the identification of new molecular markers, use of molecular markers to score segregation in breeding lines, employment of Bayesian statistics, and classical statistical plant breeding. Documents SCA with WSU. Formerly 5348-21220-003-09S (07/08).
3. Progress Report
Many wheat varieties lack seed dormancy leading to a tendency for mature grain to germinate on the mother plant when conditions are cool and rainy before harvest. ABA hypersensitive wheat mutants were isolated in both white and red wheat kernel varieties. However, the mutants in the red background eventually after-ripened during dry storage at room temperature and “lost” their phenotype. Also, the phenotype in a red kernel wheat could only be scored when seeds had after-ripened sufficiently to allow germination, but not so much that all ABA sensitivity was lost. This “phenotypic window” made genetic analysis of these mutants difficult. It was much easier to score the ABA hypersensitive germination phentoype in a soft white wheat background. These white wheat lines show increased resistance during preharvest sprouting testing. This project was performed by two Washington State University graduate students. Their progress was monitored through weekly laboratory meetings and through biweekly individual meetings. Progress was discussed with the collaborating Washington State University wheat breeder at least on a monthly basis. A progress report was generated annually.