Rice Pi-ta gene confers resistance to the major pathotypes of the rice blast fungus in the United States

The Pi-ta gene in rice prevents the infection by Magnaporthe grisea strains containing the AVR-Pita avirulence gene. The presence of Pi-ta in rice cultivars was correlated completely with resistance to two major pathotypes. IB-49 and IC-17, common in the U.S. blast pathogen population. The inheritance of resistance to IC-17 was investigated further using, a marker for the resistant Pi-ta allele in an F-2 population of 1,345 progeny from a cross of cv. Katy with experimental line RU9101001 possessing and lacking, respectively, the Pi-ta resistance gene. Resistance to IC-17 was conferred by a single dominant gene and Pi-ta was not detected in Susceptible individuals. A second F-2 Population of 377 individuals from a reciprocal cross between Katy and RU9101001 was used to verify the conclusion that resistance to IC-17 was conferred by a single dominant gene. In this cross. individuals resistant to IC-17 also were resistant to IB-49. The presence of Pi-ta and resistance to IB-49 also was correlated with additional crosses between 'Kaybonnet' and 'M-204'. which also possess and lack Pi-ta, respectively. A pair of primers that specifically amplified a susceptible pi-ta allele was developed to verify the absence of Pi-ta. We suggest that Pi-la is responsible for resistance to IB-49 and IC-17 and that both races contain AVR-Pita genes.