Genetic markers for a gene that helps rice resist a destructive fungus have been discovered by Agricultural Research Service scientists.

Plant molecular geneticist Robert Fjellstrom and research leader Anna McClung at the ARS Rice Research Unit in Beaumont, Texas, found the markers that protect rice from the rice blast fungus Magnaporthe oryzae, which causes blast disease.

Rice blast disease causes economically significant crop losses annually and is estimated to destroy enough rice to feed more than 60 million people. The fungus can infect the root, leaves, and stems of the plant. Once embedded, the fungus can produce structures that can also invade the plant's vascular system, blocking the transport of nutrients and water, and producing lesions on the aboveground plant parts.

The genetic markers are linked to the Pi-z blast resistance gene in rice. The Pi-z gene confers resistance to many strains of the blast fungus in the United States and throughout the world, so these markers are quite valuable for selecting and breeding disease resistant rice cultivars.

The markers 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 gene's presence. Rice breeders have already been able to use these markers to select for highly resistant rice cultivars in California and Texas.

Preliminary analysis of a cross between the rice varieties "Zenith" and "Pi-2" -- which carry the Pi-z and Pi-2 resistance genes, respectively -- indicate that the genetic factors encoding their separate resistance reactions are not the same, but are very tightly linked. The Pi-z markers reported here provide rice breeders and geneticists with a valuable tool for marker-aided selection of the Pi-z gene.