Yulin Jia and
United States Department of Agriculture-Agriculture Research Service, Dale Bumpers National Rice Research Center, Stuttgart, AR 72160, U.S.A.
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Accepted 17 January 2008.
Resistance to the blast pathogen Magnaporthe oryzae is proposed to be initiated by physical binding of a putative cytoplasmic receptor encoded by a nucleotide binding site-type resistance gene, Pi-ta, to the processed elicitor encoded by the corresponding avirulence gene AVR-Pita. Here, we report the identification of a new locus, Ptr(t), that is required for Pi-ta--mediated signal recognition. A Pi-ta--expressing susceptible mutant was identified using a genetic screen. Putative mutations at Ptr(t) do not alter recognition specificity to another resistance gene, Pi-ks, in the Pi-ta homozygote, indicating that Ptr(t) is more likely specific to Pi-ta--mediated signal recognition. Genetic crosses of Pi-ta Ptr(t) and Pi-ta ptr(t) homozygotes suggest that Ptr(t) segregates as a single dominant nuclear gene. A ratio of 1:1 (resistant/susceptible) of a population of BC1 of Pi-ta Ptr(t) with pi-ta ptr(t) homozygotes indicates that Pi-ta and Ptr(t) are linked and cosegregate. Genotyping of mutants of pi-ta ptr(t) and Pi-ta Ptr(t) homozygotes using ten simple sequence repeat markers at the Pi-ta region determined that Pi-ta and Ptr(t) are located within a 9-megabase region and are of indica origin. Identification of Ptr(t) is a significant advancement in studying Pi-ta--mediated signal recognition and transduction.
Additional keywords:disease resistance.
The American Phytopathological Society, 2008