Submitted to: Molecular Genetics and Genomics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/3/2002
Publication Date: 6/11/2002
Citation: Chauhan, R., Farman, M., Zhang, H.B., Leong, S.A. 2002. Genetic and Physical Mapping of a Rice Blast Resistance Locus, PiCO39(t), that Corresponds to the Avirulence Gene AVR1-CO39 of Magnaporthe grisea. Molecular Genetics and Genomics. 267:603-612. Interpretive Summary: Rice blast disease is the most important fungal disease of rice worldwide. Genetic resistance continues to be the most sustainable method of disease control. However, genetic resistance is rapidly overcome by the evolution of the pathogen to overcome host resistance. We have genetically identified a new host resistance gene and the DNA in the corresponding region of the genome. The availability of the gene for disease resistance opens the door to transfer of the gene to different varieties of rice or other economically important cereals and grasses to create resistance to fungal disease.
Technical Abstract: We have identified, genetically mapped and physically delineated the chromosomal location of a new rice blast resistance locus, designated Pi-CO39(t). This locus confers resistance to Magnaporthe grisea isolates carrying the AVR1-CO39 avirulence locus. The AVR1-CO39 locus is conserved in non-rice (cereals and grasses)-infecting isolates of M. grisea, making Pi-CO39(t) useful for engineering M. grisea resistance in rice and other cereals. The resistance in the rice line CO39 was inherited as a single dominant locus in segregating populations derived from F 2 and F 3 crosses between disease-resistant (CO39) and susceptible (51583) rice genotypes. Microsatellite, RFLP and resistance gene analog (RGA) markers were used to map the Pi-CO39(t) locus to a 1.2-cM interval between the probenazole-responsive (RPR1) gene (0.2 cM) and RFLP marker S2712 (1.0 cM) on the short arm of rice chromosome 11. RFLP markers G320 and F5003, and resistance gene analogs - 1 - RGA8, RGA38 and RGACO39 were tightly linked to the Pi-CO39(t) locus (no recombination detected in a sample of ~2400 gametes). A large-insert genomic library of CO39 was constructed in the binary plant transformation vector pCLD04541. A library screen using RGA8, RGA38 and probes derived from the ends of CO39 clones, as well as BAC end probes from the corresponding locus in the rice cv. Nipponbare, resulted in the assembly of three CO39 contigs of 180 kb, 110 kb and 145 kb linked to the Pi-CO39(t) locus. A 650-kb contig was also constructed representing the susceptible locus, pi-CO39(t), in the Nipponbare genome. The two genomes are highly divergent with respect to additions, deletions and translocations at the Pi-CO39(t) locus, as revealed by the presence or absence of mapping markers.