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
It is essential to understand how hormones control the balance between wheat grain dormancy and germination in wheat. Too little dormancy leads to problems with pre-harvest sprouting, the germination of mature grain on the mother plant when conditions are cool and rainy before harvest. Seed must loose dormancy rapidly after harvest, or too much dormancy leads to uneven germination , poor stand, and reduced yield. Mutants with altered response to the seed dormancy hormone abscisic acid (ABA) were isolated in white and red wheat kernel varieties, and evaluated too see which new alleles would provide the optimal balance between dormancy and germination. An ABA hypersensitive allele recovered in soft white spring Zak showed increased dormancy, but after-ripened rapidly suggesting that it would work well to decrease seed dormancy without having a negative impact on seed emergence. Four ABA insensitive lines were isolated in hard red spring Scarlet. Such alleles may be used to improve emergence of hard red winter wheat. This project was performed by one Washington State University graduate student and one postdoctoral fellow. Their progress was monitored through weekly laboratory meetings and through biweekly individual meetings. A progress report was generated annually.