Genetic analysis and molecular mapping of Pitb with broad-spectrum resistance to Magnaporthe oryzae in rice

Zixuan 2 is a broad spectrum-resistance indica subspecies (Oryza sativa ssp. indica) with a high resistance to 15 Magnaporthe oryzae strains from ZA, ZB, and ZC. The F1 generation of hybrid between Zixuan 2 and Lijiangxintuanheigu showed significant resistance to rice-blast pathogen ZB13, and the ratio of resistant plants to susceptible plants was 3:1, indicating that the resistance of Zixuan 2 to rice blast is controlled by a single dominant karyogene or a quantitative trait locus, designated here as Pitb. Molecular marker analysis showed that the rice blast-resistance gene is located on the terminal short arm of chromosome 12 between IN936 and IN950, with a genetic distance of 3.0 cM and physical distance of 143 kbp. In addition, the localization found that Pitb was coseparated with marker IN937. The genetic data and recombination populations provided in this study will enable further fine-mapping and cloning of the resistance gene.