| Rice blast is caused by the fungus Pyricularia grisea (syn: Magnaporthe grisea (Herbert) Barr), and is one of the most devastating diseases affecting rice. The potentially devastating economic impact resulting from blast infection has prompted worldwide efforts to product blast resistant rice varieties. The primary mechanism for resistance is through naturally occurring blast resistance genes.; One way to improve the scope and durability of blast resistance is to “pyramid” resistance genes by crossing varieties with complementary genes to provide multigenic resistance against a wide spectrum of blast races. We have developed DNA markers for several blast resistance genes, which together confer resistance to all races of blast predominant in the United States. Using degenerate primer pairs based on the P-loop, nucleotide binding site, and putative hydrophobic disease resistance gene motifs of N and RPS2, as well as microsatellite markers found in public databases, we have identified DNA markers that cosegregate with each gene in a wide range of germplasm. In a range of crosses, the apparent genetic distance between these markers and blast resistance ranged from 0–13 cM.; These markers can now be used as an alternative to conventional phenotypic screening for detection of blast resistance genes. The use of these markers in breeding programs will allow rapid introgression of blast resistance into susceptible varieties as well as incorporation of multiple resistance genes into one line for a more durable blast resistance. |
