Agricultural Research Service, U.S. Department of Agriculture, and Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695-7616.
Appl Environ Microbiol. 1991 Oct;57(10):2940-5. doi: 10.1128/aem.57.10.2940-2945.1991.
We have obtained spontaneous and UV-induced stable mutants, altered in the synthesis of cercosporin, of the fungal soybean pathogen Cercospora kikuchii. The mutants were isolated on the basis of colony color on minimal medium. The UV-induced mutants accumulated, at most, 2% of wild-type cercosporin levels on all media tested. In contrast, cercosporin accumulation by the spontaneous mutants was strongly medium regulated, occurring only on potato dextrose medium but at concentrations comparable to those produced by the wild-type strain. UV-induced mutants unable to synthesize cercosporin on any medium were unable to incite lesions when inoculated onto the soybean host. Cercosporin was reproducibly isolated from all inoculated leaves showing lesions. Although cercosporin involvement in disease has been indirectly suggested by many previous studies, this is the first report in which mutants blocked in cercosporin synthesis have been used to demonstrate that cercosporin is a crucial pathogenicity factor for this fungal genus.
我们已经获得了在大豆叶斑病菌（Cercospora kikuchii）的几丁素合成中发生自发和 UV 诱导稳定突变的突变体。这些突变体是基于最小培养基上的菌落颜色分离得到的。在所有测试的培养基上，UV 诱导的突变体最多积累了野生型几丁素水平的 2%。相比之下，自发突变体的几丁素积累受到培养基的强烈调控，仅在土豆葡萄糖培养基上发生，但浓度与野生型菌株产生的浓度相当。在任何培养基上都不能合成几丁素的 UV 诱导突变体在接种到大豆宿主上时无法引发病变。从所有显示病变的接种叶片中可重复性地分离出几丁素。尽管几丁素在疾病中的作用已被许多先前的研究间接表明，但这是首次使用无法合成几丁素的突变体来证明几丁素是该真菌属的关键致病性因素的报道。
