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Rice Pi-ta gene Confers Resistance to the Major Pathotypes of the Rice Blast Fungus in the United States

First, second, and ninth authors: U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) Dale Bumpers National Rice Research Center, Stuttgart, AR 72160; second and eighth authors: Institute of Nuclear Agricultural Sciences, Zhejiang University, Hangzhou, P.R. China 310029; third author: USDA-ARS Rice Research Unit, Beaumont, TX 77713; fourth and seventh authors: Rice Research and Extension Center, University of Arkansas, Stuttgart 72160; fifth author: Bangladesh Institute of Nuclear Agriculture, Mymensingh 2200, Bangladesh; and sixth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701

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 F₂ 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 F₂ 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-ta is responsible for resistance to IB-49 and IC-17 and that both races contain AVR-Pita genes.

Additional keywords: Oryza sativa, Pyricularia.