爪哇根结线虫Mi-毒性和无毒近等基因系的制备及其遗传变异的初步分析

爪哇根结线虫是以孤雌生殖方式繁殖的农作物重要病原物，通过将爪哇根结线虫-无毒群体在抗病番茄品种Momotaro上连续选择19代，获得了一对针对抗性基因Mi的毒性和无毒近等基因系，用102种引物对该近等基因系进行随机扩增多态性DNA（RAPD）分析显示，除一种引物外两者的RAPD带谱基本一致，证实了该毒性和无毒群体的基因组组成十分近似，对一种引物扩增出的一个无毒群体特异性的RAPD片段进行了克隆，Southern杂交结果提示该多态性片段及其同源序列在毒性选择过程中被从毒性线虫的基因组中删除，但DNA序列分析和数据库检索表明，该片段与迄今发表的核酸序列均不存在显著的同源性，因此尚无法预测其潜在的功能性，爪哇根结线虫Mi-毒性和无毒近等基因系的制备为进一步鉴定和分离该线虫毒性相关基因打下了坚实的基础。

Preparation of Meloidogyne javanica Near-isogenic Lines Virulent and Avirulent Against the Tomato Resistance Gene Mi and Preliminary Analyses of the Genetic Variation Between the Two Lines

Meloidogyne javanica ,reproducing by mitotic parthenogenesis,is an economically important pathogen of a wide range of crops. A pair of near isogenic lines virulent and avirulent toward the tomato resistance gene Mi were prepared for M. javanica by continuously selecting an avirulent population on the resistant tomato cultivar Momotaro over 19 generations. Random amplified polymorphic DNA (RAPD) analysis with 102 primers revealed that RAPD patterns were highly conserved between the virulent and avirulent lines,confirming that the two lines were genomically very similar. Nevertheless,with one of the primers a distinct polymorphic fragment,specific for the avirulent line,was amplified. Southern hybridization results indicated that the polymorphic fragment and its homologs were deleted from the genome of the virulent line during the process of virulence acquisition. Sequence analysis and homology searches of public data bases,however,revealed no published sequences significantly similar to the sequence of the fragment,precluding a prediction of the potential function of the sequence. The successful preparation of the near isogenic Mi virulent and avirulent lines laid a firm foundation for the further identification and isolation of virulence related genes in M.javanica.