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POSTERS: Late Breaking II

P-672 - Assessing the utility of BLAST-based genome analysis for avirulence gene detection and pathogenicity profiling in rice blast fungus

Tuesday, August 5, 2025
10:15 AM - 11:00 AM HST
Location: Exhibit Hall 3
Abstract Text:

To overcome the limitations of artificial inoculation-based differential systems, we aimed to develop a new method to evaluate rice blast pathogenicity. In this study, we sequenced the genomes of 72 isolates collected in Bangladesh and searched for known avirulence gene sequences using BLAST. Sequences with 100% identity were considered to possess the avirulence gene, while those with no matching sequences were regarded as lacking the gene. To evaluate the sensitivity of this method, we compared these results with previous inoculation test scores of the same isolates. We also assessed the presence or absence of avirulence genes using DNA markers developed for their identification.
For AVR-Pia, AVR-Pii, and AVR-Pik, the BLAST-based method showed 100% sensitivity, with no false negatives observed. DNA marker analyses for AVR-Pia and AVR-Pii showed sensitivities of 93.3% and 100%, respectively, while that for AVR-Pik was 70.7%. This lower sensitivity may be due to the presence of multiple allelic variants of the AVR-Pik locus, making it difficult to detect all variants using a single DNA marker. In contrast, for AVR-Pizt and AVR-Pi9, both BLAST and DNA marker analyses showed sensitivities below 30%. These results suggest that, for these genes, pathogenicity may be determined not by the gene sequences themselves but by genetic factors related to gene expression regulation. Although the BLAST-based differential system developed in this study has several limitations, it provides valuable insights for future research.