臺灣稻熱病菌AVR-Pib、AVR-Pita1和AVR-Pi9基因多型性鑑定及族群動態分析

Abstract

Rice is an important staple food consumed by an estimated 3.5 billion people worldwide. Rice blast caused by Magnaporthe oryzae is a dangerous threat to rice production and can reduce rice productivity significantly. Breeding and deployment of resistant variety is one of the effective measures to manage blast disease. However, breakdown of field resistance has been occurred frequently due to highly dynamic and quickly evolved pathogen population in the fields. Blast vertical resistance in rice generally follows a gene-for-gene relationship in which the host plant carrying a specific resistance (R) gene shows resistance against the pathogen with the corresponding avirulence (AVR) gene. Therefore, characterizing and monitoring the genotypes and evolution of AVR genes among field isolates are important tasks to sustain field resistance. Utilizing 31 IRRI LTH IRBL monogenic lines that carry single R genes, 9 genotypes of AVR-Pib gene and 12 genotypes of AVR-Pita1 gene among Taiwan rice blast fungus population were revealed. Furthermore, none of mutation can be identified in the open reading frame of AVR-Pi9 gene. Screening of three important AVR genes, AVR-Pizt, AVR-Pik and AVR-Pib, can differentiate current Taiwan rice blast fungus population into 21 groups, which stand for 8 physiological races based on their abilities to infect the rice lines or varieties containing Pizt, Pik and Pib genes. Based on the population analyses, Taitung contained the most diverse pathogen population with 10 different lineages and Taoyuan had the simplest population with only 3 lineages. Moreover, panicle blast outbreak which occurred in Lucao, Chiayi and Shanhua, Tainan in 2020 was likely caused by new and unique lineages distinct from the common pre-existing population. Taken together, we hope our pathogen surveillance studies will provide the information to prevent blast epidemics and also the foundation for sustainable rice production.