Genetic distribution of the avirulence gene AVRPiz‐t in Thai rice blast isolates and their pathogenicity to the broad‐spectrum resistant rice variety Toride 1

Abstract

Rice blast disease, caused by the filamentous fungus Pyricularia oryzae, is one of the most destructive diseases in rice worldwide. Breeding of resistant rice cultivars remains a cost‐effective and environment‐friendly means for controlling blast disease, but the resistance tends to break down over time because of the pathogen's rapid adaptation. In this study, AVRPiz‐t gene sequences of 46 rice blast isolates were evaluated using a Southern blot analysis. The AVRPiz‐t gene was present in 24 of 46 (52.2%) rice blast isolates. The pathogenicity assay showed that all blast isolates were avirulent against Japanese rice cv. Toride 1, which carries several rice blast resistance genes including Piz‐t, Pii, Pi37, and Pi‐ta. Screening for the Piz‐t gene in Thai rice germplasm revealed that less than 20% of rice varieties harbour the Piz‐t gene. Therefore, the Toride 1 rice variety could serve as an effective donor of rice blast resistance to be used in rice breeding programmes in Thailand. This study provides evidence for co‐evolution between the rice blast resistance gene Piz‐t and the rice blast fungal avirulence gene AVRPiz‐t. Understanding this relationship will facilitate the sustainable development of breeding for rice blast resistance in the future.