Molecular characterization of rice blast fungus (Pyricularia oryzae) from West Sumatra and their virulence to several rice cultivars

Global rice production is severely impacted by rice blast disease, which is a devastating condition caused by the fungal pathogen Pyricularia oryzae. Many countries have reported blast diseases associated with rice yield loss. In Indonesia, this disease also destroys rice production in several rice fields in West Java, East Java, Central Java, Sumatra, and Sulawesi. The objectives of this study were to identify rice blast fungal isolates in West Sumatra and assess the resistance level of eight local and modern rice genotypes to this disease. Additionally, the rice genotypes were also evaluated for the presence of Pi genes associated with blast resistance by utilizing 25 simple sequence-repeats (SSR) markers known to be linked to rice blasts. The seedlings of all rice genotypes were exposed to fungal isolates to determine their blast resistance capacity based on leaf morphological traits. Before conducting blast resistance testing, the local isolates of rice blast fungus were molecularly identified by aligning sequences in a pairwise comparison. Based on the identification process, three P. oryzae (MoK19-49, MoK19-45, and MoK19-28) fungal isolates were identified. The confirmed P. oryzae isolate MoK19-28 was then used to assess the blast resistance of the rice genotypes using the SES-blast test. The resistance levels of all genotypes were evaluated by observing the morphology of infected leaves for 24 days. Four genotypes, namely Cantik Manis (CM), Bungo Sungkai (BS), Inpari 48 Blas (IB), and Inpago 9 (Ip9), exhibited resistance to leaf blast caused by P. oryzae isolate MoK19-28. Meanwhile, Pulau Batu (PB), Mundam Putiah (MP), and IR64-Sub1 (IR) displayed intermediate resistance to the disease. In contrast, the blast fungus P. oryzae isolate MoK19-28 severely impacted the Kuriak (K) genotype. The rice variety IB contains several Pi genes, specifically Pi1, Pi9, Pikh, and Pi37, which are associated with enhanced resistance to leaf blast caused by P. oryzae isolate MoK19-28. This genetic characteristic sets it apart from susceptible genotypes. This work has successfully identified multiple blast-resistant rice genotypes that could potentially be used in future rice improvement initiatives.