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United States Department of Agriculture

Agricultural Research Service

Research Project: RESPONSE OF DIVERSE RICE GERMPLASM TO BIOTIC AND ABIOTIC STRESSES

Location: Dale Bumpers National Rice Research Center

Title: Field resistance expressed when the PI-TA gene is compromised by Magnaporthe oryzae

Authors
item Lee, Fleet -
item Cartwright, Richard -
item Jia, Yulin
item Correll, James -

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: October 30, 2008
Publication Date: April 6, 2009
Citation: Lee, F.N., Cartwright, R.D., Jia, Y., Correll, J.C. 2009. Field resistance expressed when the PI-TA gene is compromised by Magnaporthe oryzae. In: Wang, G.-L., Valen, B., editors. Advances in Genetics, Genomics and Control of Rice Blast Disease. Springer Science and Media. p. 281-290.

Interpretive Summary: Field blast resistance is considered to be more durable and effective because it does not rely on any specific pathogen race. In the present study, more stable resistance was observed in cultivars Katy, Drew, Ahrent and Cybonnet carrying Pi-k and Pi-ta than a cultivar ‘Banks’ that contains Pi-ta but lacks Pi-k. After 2004, blast epidemics were still observed in other ‘Banks’ production fields but have not been observed in other cultivars containing Pi-ta including ‘Drew’, ‘Ahrent’ and ‘Cybonnet’. The Pi-ta allele in ‘Banks’ was shown to confer resistance to all contemporary blast races except IE-1k and was determined to be molecularly identical to the Pi-ta allele in ‘Katy’. An increase in leaf blast severity was observed in moisture-stress tests using Banks suggesting additional resistance gene Pi-k may enhance Pi-ta gene efficacy against race IE-1k under field conditions. The data suggest that the Pi-ta gene functions as a partial resistance gene in ‘Katy’, ‘Ahrent’, ‘Cybonnet’, ‘Drew’, ‘Banks’, ‘Tetep’ and ‘Tadukan’ in regard to the broadly virulent blast pathogen races IE-1k and IB-33.

Technical Abstract: The Pi-ta gene provided 14 years of durable resistance to contemporary field population of Magnaporthe oryzae in southern USA rice production areas before being overcome during 2004 in ‘Banks’, a Pi-ta-based cultivar, by race IE-1k of the blast pathogen. Previously detected in production fields in 1994, the rarely recovered race IE-1k appeared to be poorly adapted to local conditions. Although stable molecular variations were defined in field isolates from ‘Banks’, virulence bioassays do not distinguish between isolates from Banks and the type race IE-1k isolate. After 2004, blast epidemics were noted in other ‘Banks’ production fields but have not been observed in other cultivars containing Pi-ta including ‘Drew’, ‘Ahrent’ and ‘Cybonnet’. The Pi-ta allele in ‘Banks’ still confers resistance to all contemporary blast races except IE-1k and was determined to be molecularly identical to the Pi-ta allele in ‘Katy’. ‘Banks’ does not contain the minor blast resistance genes Pi-kh or Pi-ks that are present in ‘Drew’, ‘Ahrent’ and ‘Cybonnet’. An increase in leaf blast severity observed in moisture-stress tests using Pi-ta based cultivars suggests additional resistance genes, such the Pi-kh and Pi-ks, enhance Pi-ta gene efficacy against race IE-1k under field conditions. The data suggest that the Pi-ta gene functions as a partial resistance gene in ‘Katy’, ‘Ahrent’, ‘Cybonnet’, ‘Drew’, ‘Banks’, ‘Tetep’ and ‘Tadukan’ in regard to the broadly virulent blast pathogen races IE-1k and IB-33.

Last Modified: 9/2/2014
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