Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2005
Publication Date: February 1, 2006
Citation: Fjellstrom, R.G., McClung, A.M., Shank, A.R. 2006. SSR markers closely linked to the Pi-z locus are useful for selection of blast resistance in a broad array of rice germplasm. Molecular Breeding. 17(2):149-157.
Interpretive Summary: Rice blast disease is a serious threat to rice production in the USA. There are natural genes for blast disease resitance in rice and these genes are an environmentally friendly way to combat disease losses. DNA markers have been developed for a blast resistance gene in rice that is called Pi-z. The Pi-z gene confers resistance to many forms of the fungus that causes blast in the USA and throughout the world, so these markers are quite valuable for selecting and breeding disease resistant rice cultivars. The markers presented in this research are also highly beneficial because they are located closer to the Pi-z gene than previously developed markers for this gene, making them extremely accurate in predicting the presence of this useful gene. Rice breeders have already been able to use these markers to select for highly resistant rice cultivars in California and Texas.
Pi-z is a disease resistance gene that has been effectively used to combat a broad-spectrum of races of the rice blast fungus Magnaporthe grisea. Although DNA markers have been reported for selection of the Pi2(t) and Pi-z resistance genes at the Pi-z locus, markers that are more tightly linked to the Pi-z locus would benefit rapid and effective cultivar development. Analysis of the publicly available genome sequence of Nipponbare near the Pi-z locus revealed numerous SSRs that could be converted into markers. Three SSRs on rice BAC AP005659 were found to be very tightly linked to the Pi-z locus, with one marker, AP5659-3, co-segregating with the Pi-z resistance reaction. The Pi-z factor conferring resistance to two races of blast was mapped to a 57 kb region on the physical map of Nipponbare in a location where the Pi2(t) gene was physically mapped. Two SSR marker haplotypes were unique for cultivars carrying the Pi-z gene, which indicates these markers are useful for selection of resistance genes at the Pi-z locus in rice germplasm.