1a. Objectives (from AD-416):
To Generate transgenic wheat plants that overexpress TaBAK1. Begin the evaluation of these transgenics for increased FHB resistance. Conduct VIGS experiments to evaluate the possible functions of three other TaBAK1-related sequences in FHB resistance, TaBAK2, 3, 4 and 5. Generate cDNA clones for transformation if any of the TaBAK1-related sequences prove to make significant contributions to FHB resistance. Continue the characterization of transgenic wheat overexpressing ethylene-signaling genes. Continue the breeding of oat lines with Yellow dwarf virus (YDV) crown rust (CR) and stem rust (SR) resistance.
1b. Approach (from AD-416):
Efforts to make significant improvement in the resistance of wheat to Fusarium head blight (FHB) require understanding the mechanism(s) of the naturally occurring FHB resistance pathways. Quantitative Trait Loci (QTL) conferring varying degrees of FHB resistance are known and these are being used by breeders to generate useful FHB resistant wheat and barley varieties. However, none of the actual gene sequences that underlie these QTL and determine the mechanism of FHB resistance are known. Until the molecular mechanism of FHB resistance is better understood, efforts to engineer improved FHB resistance will be futile. The process of identifying the genes that are functionally essential to FHB resistance has been greatly hindered by the genetic complexities of wheat. In previous work funded by the USWBSI our group has developed a virus-induced gene silencing (VIGS) system that overcomes many of the obstacles for functional identification of genes involved in FHB resistance. Previous work has shown that wheat and barley plants that are resistant to FHB initiate complex defense responses when challenged by Fusarium graminearum. Understanding how these responses are initiated is a key question to address. Very recent results in our VIGS analyses have implicated a receptor-like protein, TaBAK1, as playing a key role in FHB resistance. In model plants systems this proteins functions in the perception of conserved pathogen-associated molecular patterns (PAMPs), leading to PAMP-triggered immunity (PTI). The discovery of a receptor-kinase protein that may play a key role in activating FHB resistance offers an excellent opportunity to engineer improved FHB resistance, and thereby directly serves the primary objective of the USWBSI Gene Discovery and Engineering Resistance research area. Efforts are being made to breed more disease resistant oat lines by introgressing resistance loci from the wild oat Avena strigosa Accession 6688 Resistance to Yellow dwarf virus (YDV), crown rust (CR) and stem rust (SR) has been incorporated into elite oat lines and has undergone three backcross cycles. Lines with excellent agronomic properties have been recovered that contain all three A. strigosa resistance loci. With further selection this material will be ready for germplasm release.
3. Progress Report:
During FY13 transgenic wheat plants were generated in a wheat line that is normally susceptible to this disease, so if these genes are effective these lines will display increased resistance.Seeds from these transformants were bulked and are about to be tested in the greenhouse for improved FHB resistance. Virus-induced gene silencing constructs to specifically assess the role of other candidate genes in Fusarium head blight in FHB resistance have been constructed and will be tested during FY14. An additional focus of this project is the improvement of oat germplasm through introgression of resistance to Yellow dwarf virus (YDV), crown rust (CR) and stem rust (SR), from the Avena strigosa Accession 6688. This material has now undergone the fourth backcross to elite oat lines and families exhibiting excellent agronomic characteristics as well as resistance to all three pathogens have been recovered.