Marker development for rice blast resistance gene Pi66(T) and application in the USDA rice mini-core collection

Molecular markers are useful for the identifi­cation of critical genes controlling agricultural traits of interest in crop germplasm and for the use of these genes in crop improvement using marker-assisted selection (MAS). The improve­ment of blast disease resistance of rice (Oryza sativa L.) varieties is one of the major goals for rice breeders. The blast resistance (R) gene Pi66(t) was previously mapped to a 129-kb genomic region on chromosome 11, where six candidate R genes were predicted. To help rice breeders in rice blast resistance MAS breeding, we developed three polymerase-chain-reaction (PCR)-based molecular markers, WRKY41, NBS-LRR-970-1, and NBS-LRR-970-2, for the Pi66(t) locus. The validation of two mark­ers, WRKY41 and NBS-LRR-970-1, suggested they cosegregated with the Pi66(t) gene in two recombinant inbred line (RIL) populations. The application of two markers in a USDA–ARS rice mini-core collection indicated that NBS-LRR-970-1 was a Pi66(t)-linked specific marker. The developed marker not only can be used to identify resistant lines with the Pi66(t) gene in mapping populations but also can be used in screening rice germplasm with a broad genetic background. Taken together, these newly devel­oped markers and newly identified rice germ­plasm lines carrying the Pi66(t) gene will provide essential tools and materials for rice breeders in MAS breeding.