DNA Marker Analysis of Blast Resistance Genes Pib and Pita in IRRI-Bred Rice Varieties Comparing with Gene Estimation by a Differential System

Blast resistance genes are important in rice (Oryza sativa L.) improvement programs. The DNA markers linked to resistance genes are a powerful tool to detect the presence of genes and are widely used to select breeding materials through marker-assisted selection. This study was conducted to evaluate the detection ability of DNA markers for rice blast resistance genes Pib and Pita in IRRI-bred rice varieties. Forty-two Indica-type varieties, which have been previously analyzed for the presence of Pib and Pita by conventional genetic analysis using a differential system involving standard blast isolates (Pyricularia grisea Sacc.) from the Philippines, were tested. To estimate the presence of Pib and Pita, previously reported PCR-based dominant markers were used. The target DNA fragments of Pib using Sub3-5 were amplified in 40 varieties but not in two varieties. Also, the target DNA fragments of Pita using three gene-specific markers were amplified in 27 or 28 varieties but not in 14 or 15 varieties. The results of DNA marker analysis of the 42 IRRI-bred rice varieties were almost the same as those of previous gene estimation of Pib and Pita by the differential system. It suggests that the efficiency of detecting blast resistance genes through use of DNA markers depends on the rice variety and the DNA markers. The proper markers for the Pita gene provide a basis for stacking other blast resistance genes into high-yielding and good-quality advanced breeding rice lines.