Screening of Blast Resistance Genes from South Tapanuli Rice Cultivars, North Sumatra, Indonesia

Rice blast disease caused by a phytopathogenic fungus, Magnaporthe oryzae, has been considered as a major threat to global rice productivity, including Indonesia. South Tapanuli is a regency in North Sumatra, known for its intensive and significant rice production activities. A collection of 13 rice cultivars originating from the region, is claimed for its resistances against the rice blast disease based on the practices by the local farmers. Molecular screening of blast resistance (R) genes was initiated to the 13 accessions using the Polymerase Chain Reaction (PCR) targeting five blast resistance (R) genes, Pup1, Pi-37, Pi-d2, Pi-ta², Pib and Pi-kh. Out of the 13 accessions, the Pi-d2, Pi-ta² and Pib were detected in all cultivars, showing 100% of R gene frequency. The second dominant, Pup1 and Pi-37 gene frequencies were 76.9 and 61.5%, respectively while the least dominant, Pi-kh gene frequency was 15.4%. The number of R genes detected among cultivars was ranged between 3 to 6 genes. The genetic associations among thirteen germplasms were determined using unweighted pair group method with arithmetic mean (UPGMA) analysis. Cluster analysis revealed that the least blast-resistant cultivars: Putri Kembar, Silatian and Siganteng, were grouped into cluster 1, showing polymorphism for Pi-d2, Pi-ta² and Pi-b. The high-resistant cultivars, Martabe-Sicondong and Sayuti, Sitolas, Pulo Raja, Pulo Pandan, Siporang and Pulo Manggis, were grouped into cluster 2 and 3, respectively. The medium blast-resistant cultivars, IR 64 and Sitampan were grouped into cluster 4, showing polymorphism for Pup1, Pi-d2, Pi-ta² and Pi-b. These results indicated that the utilization of blast-resistant cultivars in North Tapanuli was supported by the presence of R genes.