南方根结线虫中国分离群体种内变异分析

为调查我国不同地区和不同寄主上的根结线虫Meloidogyne spp.种类分布以及群体变异情况，基于酯酶和苹果酸脱氢酶同工酶图谱及SCAR分子标记技术对2017—2019年从6省19种植物根部组织分离到的40个根结线虫群体进行鉴定，针对南方根结线虫M.incognita群体分别通过寄主鉴别法进行生理小种鉴别，利用携带Mi抗性基因的番茄进行毒力测试，对2龄幼虫的口针长度和体长进行测量，并对核糖体ITS和线粒体Nad5基因序列进行比较分析。结果显示：根结线虫分离群体经鉴定包括38个南方根结线虫群体和2个象耳豆根结线虫M.erterolobii群体；38个南方根结线虫群体中有35个群体被鉴别为1号生理小种，其余3个群体被鉴别为2号生理小种；发现1个南方根结线虫群体CN19可在携带Mi抗性基因的番茄上侵染繁殖，为毒性群体，其余群体无法进行侵染和繁殖，为无毒群体。南方根结线虫群体2龄幼虫的口针长度和体长均差异较大，而不同寄主来源分离群体的ITS和Nad5基因序列也存在一定变异。基于ITS和Nad5基因序列构建的系统发育树将所有根结线虫群体归为南方根结线虫和象耳豆根结线虫组成的2个独立分支，但不能确定南方根结线虫不同群体的分子进化与其寄主来源和地理分布之间的相关性。

Intraspecific variability of the southern root-knot nematode Meloidogyne incognita in China

To better understand the geographical distribution, and the pathogenic and genetic variability of the root-knot nematode, a survey was carried out in six provinces of China in 2017-2019. Forty root-knot nematode populations were recovered from 19 host plants and identified by using esterase (Est) and malate dehydrogenase (Mdh) phenotypes as well as the diagnostic SCAR marker. Races of Meloidogyne incognita populations were further characterized using pathogenic tests (host plant range and virulence) and morphometrics. The ITS and NADH dehydrogenase subunit 5 (Nad5) genes were PCR-amplified from them, and used to generate the phylogenetic trees for these root-knot nematode populations. The results showed that 38 root-knot nematode populations belonged to M. incognita with 35 in race 1 and three in race 2, while the other two populations were identified as M. enterolobii. Sample CN19, which could multiply in the resistant tomato carrying Mi gene, was identified as virulent, while other populations were avirulent. Comparative analysis revealed that morphologic traits (body and stylet lengths) of the second-stage juvenile varied remarkably among populations, while ITS and Nad5 sequences also exhibited intraspecific variation to some extent. The phylogenetic trees based on ITS and Nad5 suggested that these populations could be clustered into two main clades, M. incognita and M. enterolobii. However, the relationship between molecular evolution of different populations of M. incognita and the host origins or geographical distance could not be determined.