CONICET | Buscador de Institutos y Recursos Humanos

Blast disease caused by the hemibiotrophic Magnaporthe oryzae is the most important disease for rice crop. Common strategies for its control are the use of resistant cultivars and pesticides in an integrated pest management system. Over the years, rice blast resistance genes have been identified and recent molecular characterization of broad spectrum genes has allowed the development of molecular markers for marker-assisted selection. Major blast resistance genes against M. oryzae were screened in a number of Argentinean rice varieties. Sixty-four cultivars that are historically significant to rice breeding and production in Argentina were survey for the presence of Pi5, Pita, Pib and Pi2/Piz-t genes and for polymorphism of SSR markers linked to Pi1, Pi33, Piz, Pib and Pik. Twelve selected rice cultivars were also characterized with 11 RGAs markers and pathogenicity test using 50 isolates representative of M. oryzae populations from Argentina. Genetic relationship of rice varieties based on molecular markers linked to Pi genes, RGAs, and pathogenicity assays were revealed. Also, molecular characterization of M. oryzae avirulence alleles of Avr-Pita, Avr-Ace1 and AvrPiz-t genes were evaluated in native isolates previously characterized using Pot2-DNA fingerprinting and virulence assays on a set of differential rice cultivars and near-isogenic lines carrying different Pi genes. Four different haplotypes of Avr-pita gene were detected in seven sequenced alleles. Frequency of resistance and Avr genes in rice varieties and native M. oryzae isolates were registered. Polymorphic combinations allowing introgression of the broad spectrum resistance genes into a susceptible genetic background have been identified. The results will be useful for breeding on rice blast resistance for durable resistance cultivars. Supported by CONICET (PIP 0102), UNMdP (EXA553/11) and FIBA.