Department of Life Science, Fu Jen Catholic University, Xin-Zhuang District, New Taipei City, Taiwan, Republic of China.
Phytopathology. 2020 May;110(5):981-988. doi: 10.1094/PHYTO-08-19-0319-R. Epub 2020 Mar 13.
Xanthomonads were detected by using the Xan-D(CCF) medium from the brassica seeds, and their pathogenicity was determined by plant inoculation tests. It was found that some seed lots were infested with pv. , some with pv. , and some with nonpathogenic xanthomonads. The nonpathogenic xanthomonad strains were identified as , and the multilocus sequence analysis showed that the nonpathogenic strains were grouped together with pathogenic , but not with nonpathogenic strains of In addition, all isolated pv. and pv. strains were positive in the -PCR, but the nonpathogenic strains were negative. It was further found that nonpathogenic strain nE1 does not contain the entire pathogenicity island ( gene cluster; type III secretion system) and all type III effector protein genes based on the whole genome sequence analyses. The nonpathogenic strain nE1 could acquire the entire pathogenicity island from the endemic pv. and pv. strains by conjugation, but type III effector genes were not cotransferred. The studies showed that the nonpathogenic strains indeed exist on the brassica seeds, but it could be differentiated by the PCR assays on the and type III effector genes. Nevertheless, the nonpathogenic strains cannot be ignored because they may be potential gene resources to increase genetic diversity in the endemic pathogenic pv. and pv. strains.
通过使用来自 Brassica 种子的 Xan-D(CCF)培养基检测黄单胞菌，并通过植物接种试验确定其致病性。结果发现，一些种子批次受到 pv. 的侵染，一些受到 pv. 的侵染，而一些则受到非致病性黄单胞菌的侵染。非致病性黄单胞菌株被鉴定为 ，多位点序列分析表明，非致病性 菌株与致病性 菌株聚在一起，但与非致病性 菌株不聚在一起。此外，所有分离的 pv. 和 pv. 菌株在-PCR 中均为阳性，但非致病性菌株为阴性。进一步的研究发现，非致病性菌株 nE1 不含有整个致病性岛（基因簇；III 型分泌系统）和所有 III 型效应蛋白基因，这是基于全基因组序列分析得出的。非致病性菌株 nE1 可以通过接合从地方性 pv. 和 pv. 菌株中获得整个致病性岛，但 III 型效应基因没有共转移。研究表明，非致病性菌株确实存在于 Brassica 种子上，但可以通过针对 和 III 型效应基因的 PCR 检测进行区分。然而，非致病性菌株不能被忽视，因为它们可能是增加地方性致病 pv. 和 pv. 菌株遗传多样性的潜在基因资源。
