ARS | Publication request: PROGRESS IN DEVELOPING MOLECULAR MARKERS FOR TAGGING MAGNAPORTHE GRISEA PATHOTYPES IN THE USA

Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 1, 2006
Publication Date: February 15, 2006
Citation: Jia, Y., Zhou, E., Lee, F.N., Correll, J., Singh, P. 2006. Progress in developing molecular markers for tagging magnaporthe grisea pathotypes in the usa. Rice Technical Working Group Meeting Proceedings, February 29-March 1, 2006. 2006 CDROM.

Technical Abstract: The Magnaporthe grisea avirulence gene AVR-Pita encodes a telomeric associated metalloprotease conferring the efficacy of the Pi-ta gene in the southern U.S. The rice cultivars containing Pi-ta have been widely utilized since the deployment of the first Pi-ta containing cultivar, Katy, in 1989 in the US. Recently, the efficacy of Pi-ta in controlling blast disease has been challenged by virulent M. grisea isolates. A total of 70 virulent M. grisea field isolates were collected from Pi-ta containing cultivars in Arkansas rice fields and blast nurseries over the years. Differences in the degree of the virulence toward several different rice genotypes were observed among these virulent isolates. Allele-specific PCR, repetitive element-based PCR, Southern hybridization, molecular cloning, and sequencing techniques were used to analyze allelic variations at the AVR-Pita locus in these virulent isolates. Preliminary results suggest that these isolates contain a non-functional telomeric associated AVR-Pita. In one case, a Pot 3 transposon was found to insert into the protease motif of the AVR-Pita protein resulting in loss of the avirulence. The homologous sequences of avr-pita were PCR-amplified and cloned from some virulent field isolates and are being sequenced. Progress in developing reliable PCR based detection of these diverse virulent avr-pita alleles is described.