LAUSR

Rice blast caused by Magnaporthe oryzae is a dangerous threat to rice production and food security worldwide. Breeding and proper deployment of resistant varieties are effective and environment-friendly strategies to manage this notorious disease. However, highly dynamic and quickly evolved rice blast pathogen population in the field has made disease control with resistance germplasms more challenging. Therefore, continued monitor of pathogen dynamics and application of effective resistance varieties are critical tasks to prolong or sustain field resistance. Here, we report a team project involved evaluation of rice blast resistance genes and surveillance of M. oryzae field population in Taiwan. A set of IRBLs (International Rice Research Institute-bred blast-resistant lines) carrying single blast resistance genes were utilized to monitor the field effectiveness of rice blast resistance. Resistance genes such as Ptr (formerly Pita2) and Pi9 exhibited best and durable resistance against rice blast fungus population in Taiwan. Interestingly, IRBLb-B line harboring Pib gene with good field protection has recently shown susceptible lesions in some locations. To dissect the genotypic features of virulent isolates against Pib resistance gene, M. oryzae isolates were collected and analyzed. Screening of AvrPib locus revealed that majority of field isolates still maintained the wild type AvrPib status, but eight virulent genotypes were found. Pot3 insertion appeared to be a major way to disrupt the AvrPib avirulence function. Interestingly, a novel AvrPib double allele genotype among virulent isolates was first identified. Pot2 rep-PCR fingerprinting analysis indicated mutation events may occur independently among different lineages in different geographic locations of Taiwan. This study provides our surveillance experience of rice blast disease and serves as the foundation to sustain rice production.