Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2003
Publication Date: 12/10/2003
Citation: Fjellstrom, R.G., Shank, A.R., McClung, A.M. 2003. Mapping and genetic characterization of a novel blast resistance gene arising from the rice cultivar Leah. Plant and Animal Genome Conference Proceedings. P. 170.
Technical Abstract: Rice blast, caused by the fungus Pyricularia grisea, is a major disease threat to rice production wherever rice is grown. The rice blast pathogen is highly variable in most rice growing regions, where several races of the fungus having diverse combinations of avirulence genes can be found. Identification of new genes for blast resistance that broaden the spectrum of resistance in advanced germplasm is of continuing interest for rice breeders and pathologists. A novel blast resistance gene was identified in the USA cultivar Leah, which apparently originated from an outcross in the breeding selection CI 9902. Leah displays resistance to unique spectrum of USA blast races that is similar, but not identical, to the Pi-kh disease resistance gene originally identified in 'Dawn'. This similar race resistance spectrum suggested an allelic relationship to the Pi-kh gene, which was tested by molecular marker mapping analyses. F2 progeny from a cross between the cultivar M9 (with no apparent blast resistance genes) and Leah were evaluated for their disease resistance to blast race IG-1 and its association with DNA marker segregation. It was determined that the Leah factor conferring resistance to IG-1 mapped to the same region on rice chromosome 11 as the IB-54 and IG-1 resistance factors conferred by the Pi-kh gene. The resistance spectrum against USA blast races and the microsatellite haplotypes at the Pi-k locus were compared between Leah and other rice cultivars carrying a variety of described Pi-k alleles. It is concluded that Leah has a unique and previously-unidentified allele at the Pi-k locus.