Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. In order to identify efficient rice breeding materiel, pathogenicity tests followed by PCR and sequence analysis were performed on twelve rice accessions using ten blast isolates and molecular markers linked to five major blast resistance (R) genes/loci (Pi2/Pi9/Piz/Pizt, Pi5 (t)/Pii/Pi3, Pik/Pikp/Piks/Pikm, Pia and Pita) and to their corresponding avirulence (Avr) genes. At the Pi5 (t) locus, we found out that instead of the Pi5 (t), the Pi56 (t) R gene was identified in all the accessions and SNPs differentiate both R genes. At the Piz locus, R genes Piz, Pizt and Pi2 were identified in IRAT13, ARICA5 and IRAT104 respectively. At the Pik locus, Pikm and Piks were identified in accessions ARICA1 and MARATELLI respectively. In addition, the Avr-Pik gene identification in the screened isolates led either to susceptibility or resistance reaction on the known susceptible accession MARATELLI. These results confirm the fact that they might have different Avr-Pik alleles that are specifically recognized by different Pik alleles. The Pia R gene was identified in five accessions including the known susceptible accession CO39; and the pathogenicity tests revealed that CO39 was resistant to two isolates lacking Avr-Pia gene. Thus, both isolates might harbor the Avr-PiCO39 gene which as the Avr-Pia, can recognize both Pia & Pi-CO39 R genes. Pita R gene was also identified in two accessions. Thus, the outcomes of this study provide reliable information that could be useful in the breeding program for improving rice blast resistance.

Keywords: Magnaporthe oryzae, resistance gene, avirulence gene, PCR, Sequencing.