Submitted to: Proceedings Southern Region American Phytopathology Society
Publication Type: Abstract Only
Publication Acceptance Date: 12/28/2004
Publication Date: 2/25/2005
Citation: Lee, F.N., Cartwright, R.D., Jia, Y., Correll, J.C. 2005. Magnaporthe grisea race shift for virulence to the major R gene, Pita, in Arkansas. Proceedings Southern Region American Phytopathology Society. Abstract p. 116.
Technical Abstract: In 1989, following severe blast epidemics with 'Newbonnet' rice in 1986 - 1988, Arkansas plant breeders released 'Katy' rice containing the major R gene, Pi-ta that conferred resistance to U.S. M. grisea races. Although isolates from laboratory tests and race IE-1K were virulent to Pi-ta, race IE-1K was only infrequently isolated from commercial fields and field plots. Pi-ta based cultivars were widely utilized in U.S. production areas without any known reports of field infection beyond a few random plants. In August, 2004, however, severe blast disease occurred in a seed field of 'Banks' rice. Seeding records and DNA analysis of infected plant tissue confirmed the cultivar as Banks containing the Pi-ta gene. Greenhouse tests with M. grisea isolates from infected 'Banks' plants confirmed virulence on Pi-ta cultivars and all exhibited a host range similar to race IE-1K. Preliminary PCR analysis indicates Banks isolates lack a functional AVR-Pita gene. Further Rep-PCR analysis indicates the DNA profile of Banks isolates is different from known IE-1K isolates.