云南罗平田间稻瘟菌株性状及无毒基因研究

 稻瘟菌和水稻是研究禾本科作物病原-寄主互作机制的模式病理系统。云南罗平县不仅是云南省水稻主产区,栽培水稻品种多样,同时也是稻瘟病易发区,田间稻瘟菌群体组成复杂,信息流强度大。田间单孢菌株的分离和无毒基因的研究,是揭示稻瘟菌毒性变异机制和制定田间稻瘟病综合防控策略的重要基础。本研究通过单孢分离,从2017年云南罗平田间病样上分离和保存了有效单孢菌株120份,系统地进行了菌株培养性状、产孢能力、7个无毒基因存在/缺失多态性及无毒基因变异与致病性相关性的研究。研究结果表明:菌株间培养性状、产孢能力差异较大,但培养性状和产孢能力与菌株的病样源无关;ACE1、Avr-Pizt、Avr-Pita1、Pwl2、Avr-Pik、Avr-Pii和Avr-Pia 7个无毒基因在云南罗平120个田间菌株中的存在/缺失频率不同,ACE1、Pwl2和Avr-Pizt存在频率最高(100%),Avr-Pia最低(5%),Avr-Pita1、Avr-Pik和Avr-Pii分别是99%、99%和89%,并首次分离和鉴定了33个包含3个Avr-Pik等位基因拷贝的菌株;部分代表菌株接种单基因系水稻的致病性鉴定结果显示,菌株中无毒基因的完全缺失或变异能使携带相应抗病基因的单基因系水稻材料感病,表明病原通过丢弃或修饰其无毒基因逃避寄主的免疫识别,克服寄主的抗性。研究结果不仅丰富了稻瘟病菌的遗传资源,奠定了水稻-稻瘟菌互作机制研究的重要基础,而且也为云南罗平稻瘟病的综合防治提供了参考。

Studies on characterizations and avirulence genes of field Magnaporthe oryzae strains from Luoping of Yunnan Province,China

Rice and Magnaporthe oryzae (M. oryzae) constitutes an ideal pathosystem for studying host-pathogen interaction in cereals crops. Luoping County, southwest China's Yunnan Province, is a main rice-producing area and one of the major hotspots of rice blast disease. In the field, the composition of M. oryzae population is complex and the information flow is strong. The isolation of single spore strains and the study of avirulence genes are the important basis for revealing the mechanism of virulence variation of M. oryzae and the comprehensive control of rice blast disease. In this study, we isolated 120 single spore strains from the field samples collec-ted from Luoping in 2017. The morphology, sporulation capacity, presence/absence (P/A) polymorphisms of seven avirulence (Avr) genes, and the relationship between avirulence gene variation and pathogenicity of these strains were studied systematically. Our results showed that the culture characteristics and sporulation ability were diversity among strains. The P/A frequency of seven Avr genes in 120 field strains was different, in which ACE1, Pwl2, and Avr-Pizt had the highest frequency of 100%, Avr-Pia had the lowest frequency of 5%, and Avr-Pita1, Avr-Pik, Avr-Pii were 99%, 99%, and 89%, respectively. Importantly, thirty-three M. oryzae isolates containing three Avr-Pik allele copies were identified for the first time. The rice monogenic lines were susceptible to the strains with the corresponding Avr genes complete deletion or functional variation. This result indicated that pathogen could shed off or modify its Avr gene to dodge past the resistance mechanism of the host plant thus making it susceptible. Our findings not only enrich the genetic resources of M. oryzae, lay an important foundation for studying the mechanisms of rice-M. oryzae interaction, but also provide valuable information for controlling rice blast disease.