1 Department of Agroecology - Entomology and Plant Pathology, Department of Agroecology, Science and Technology, Aarhus University2 Department of Molecular Biology and Genetics - Afgrødegenetik og Bioteknologi, Department of Molecular Biology and Genetics, Science and Technology, Aarhus University3 Department of Molecular Biology and Genetics - Afgrødegenetik og Bioteknologi, Department of Molecular Biology and Genetics, Science and Technology, Aarhus University4 Department of Agroecology - Entomology and Plant Pathology, Department of Agroecology, Science and Technology, Aarhus University
Crops and their wild relatives contain several hundred genes that confer disease resistance (R genes). This pool of genes represents a vast resource for breeding resistant crops, but the identification of R genes is lengthy and laborious by classical genetic approaches. Thus, the lack of knowledge about R genes, and the pests individual R genes may provide resistance against, is a major bottleneck in plant breeding. Recently our cooperators from KU found that R genes mutated in specific domains act as dominant negatives conferring susceptibility, when introduced into plants resistant to the considered pathogen due to the presence of the wild type R gene. Based on this discovery and previous work of Arabidopsis, a strategy to match R genes to specific pathogens has been designed in wheat. In wheat cultivar ‘Bobwhite S-26’ we will establish proof-of-concept using the wheat yellow rust system. The yellow rust R gene Yr10 will be transformed into Bobwhite, and transgenic plants tested for resistance against an appropriate avirulent P. striiformis isolate harboring the AvrYr10 gene. Regenerated transgenic plants will be re-transformed with a mutated form of Yr10. The host-pathogen phenotype resulting from inoculation with the appropriate pathogen isolate will be recorded, with susceptibility of the plants as anticipated outcome. The presence or absence of Yr10 will be confirmed with a P. striiformis wild type AvrYr10 isolate and a correspondingYr10-virulent mutant isolate. For the screening strategy, we will identify an inventory of wheat R genes via deep transcriptome sequencing. A Bobwhite-specific library of expressed NB-LRR genes will be generated. Via deep sequencing, publicly available DNA sequence information will work as scaffolds for establishing correct NB-LRR cDNA contigs. We plan to screen ~100 R genes from Bobwhite cultivar. Transgenic Bobwhite lines with mutated forms of R genes will be inoculated with selected avirulent isolates of P. striiformis. Susceptibility will indicate that a mutated form of the R gene that confers resistance to a particular isolate is present in the transgenic plant, and in this way the R gene can be identified. Based on the test system developed in Bobwhite S-26, the long term aim of the project is to develop a screening strategy to identify R genes in any wheat variety showing an R gene-based resistance phenotype against specific pathogen isolates. The identified R genes can subsequently become exploited in breeding for disease resistance.