湖南桃江病圃稻瘟病菌对24个水稻抗稻瘟基因的毒性分析

稻瘟病是水稻生产上的重要病害,了解稻瘟病菌群体毒性组成是水稻抗病品种合理布局的重要基础。2012-2015年从湖南桃江病圃中不含已知抗瘟基因的水稻品种‘丽江新团黑谷’上成功分离出351个稻瘟病菌单孢菌株,在温室于水稻5叶期采用离体接种法测定了其对24个水稻抗稻瘟病单基因系的毒性,结果表明,病圃中稻瘟病菌以广谱强致病性的菌株为主,病菌对不同抗瘟基因的毒力频率在50.56%~96.67%之间,而不同年度间对24个抗性基因均具毒性的菌株出现频率在0~15%之间。对2015年的每2个抗瘟基因的联合毒力分析表明,基因两两搭配后的联合抗病系数最高、联合致病系数最低的组合是Pi-3*Pi-k(RAC=0.19,PAC=0.43)。

Virulence of Magnaporthe oryzae to 24 blast resistance genes in rice from the disease nursery at Taojiang, Hunan

Rice blast,caused by Magnaporthe oryzae,is one of the most devastating diseases of rice.To understand the virulence composition of the pathogen fungus and hence provide the basis of rational deployment of resistant rice varieties,351 isolates derived from single conidia of M.oryzae were obtained from a widely susceptible variety,i.e.‘Lijiang Xintuan Heigu’ (LTH),planted in the disease nursery at Taojiang,Hunan.The virulence assay was conducted on in vitro segments from the fifth leaves of 24 near-isogenic lines (NILs) of rice carrying single resistance genes against blast disease.The results showed that most isolates in the nursery had broad-spectrum virulence.The virulence frequency (VF) to 24 resistance genes varied from 50.56％ to 96.67％.The frequencies of the isolates showing virulent to all of the 24 resistance genes varied from 0 to 15％ in 2012-2015.According to the analysis of pathogenicity association coefficient (PAC) and resistance association coefficient (RAC)tested in 2015,the combination of two genes which had maximum RAC and minimum PAC were Pi-3 * Pi-k,with the value of 0.19 and 0.43,respectively.