1a. Objectives (from AD-416):
Agronomically important genes will be identified and deployed using a molecular genetic approach. The objectives of this cooperative agreement are to: 1. Identify loci controlling preharvest sprouting tolerance, seedling emergence and stand establishment; 2. Identify and deploy genes for drought and cold tolerance in wheat; and 3. Identify and deploy genes for stem and stripe rust resistance.
1b. Approach (from AD-416):
This project will identify loci controlling preharvest sprouting tolerance and seedling emergence. It is likely that loci providing dormancy will give better preharvest sprouting tolerance, but have a negative impact on emergence unless dormancy breaking treatments are used. Cooperator will examine the ability of wheat to emerge from deep planting, to germinate under water-limited conditions, and develop dormancy breaking conditions. ARS' research program will take a complimentary approach by examining the dormancy status of wheat varieties and elucidating the role of ABA and GA hormone signaling in the control of seed germination using wheat and Arabidopsis. ARS and the cooperator will collaborate to examine how seed dormancy and emergence properties correlate and to develop a strategy to breed for wheat that will have sufficient dormancy to resist sprouting while at the same break dormancy quickly enough to avoid problems with emergence. This will be achieved in part through assessing breeding program germplasm and wheat mutants for these properties using after-ripening time course experiments, PEG plating assays, RT-PCR analysis of ABA and GA signaling related gene expression, and strategic crosses for breeding. As part of the collaboration on the subject of drought and cold tolerance, ARS and the cooperator will use experiments under controlled greenhouse conditions to assess the mechanisms of wheat survival of these stresses. They will integrate this data, their own field data, and field data from the cooperator's program to devise new breeding strategies. Finally, both ARS and the cooperator will examine the loci providing stripe and stem rust resistance within their breeding programs. This will be achieved through test crosses, greenhouse rust infection assays to determine whether resistance genes are specific to particular rust races, and through collaborative breeding efforts.
3. Progress Report:
This project supports the parent project Objective 3 by examining the mechanisms of cold and drought tolerance in wheat. It is important to understand the mechanisms controlling wheat drought and cold tolerance. Too little cold tolerance leads to yield loss due to winter kill of winter wheat, whereas insufficient drought tolerance leads to yield loss and poor grain filling in semi-arid regions of Washington state. This year, an ARS Research Scientists and a Washington State University post-doctoral fellow identified alleles of the cold tolerance genes called CBF (CRT binding factor) associated with sensitivity or resistance to sub-freezing temperatures. Through sequencing of alleles on wheat chromosome 5A it was determined that copy number variation at CBF12, CBF14 and at Vrn-A1 determined degree of freezing tolerance in winter wheat. Future work will select these alleles for cold tolerance in breeding lines. Knowledge of this specific cold sensitive allele will advance efforts to breed for cold tolerant spring wheat. ARS Research Scientists worked with a Washington State University professor and graduate student to identify lines derived from a cross of soft white spring Alpowa to Louise that show increased drought tolerance. Future work will release a new cultivar with increased drought tolerance.