Zhang G Z, Zhang H W
Department of Plant Pathology, China Agricultural University, Beijing, 100094, China.
Plant Dis. 2007 Apr;91(4):459. doi: 10.1094/PDIS-91-4-0459C.
During the summer of 2004, a root rot was observed on 3- and 4-year-old American ginseng cultivated in the Beijing area, and in 2006, the root rot was also found in the Hebei Province. The root epidermis appeared light brown with irregular lesions in the early stage. Sometimes the lesions had defined edges and were striped. In the later stages of the disease, the roots had splits in the epidermis and a rotted cortex causing them to lose commercial value. Plants wilted when the roots were severely damaged. The diseased roots were assayed for plant parasitic nematodes. A plant parasitic nematode was identified as Ditylenchus destructor on the basis of the following characteristics (1): stylet length ranged from 9.2 to 13.3 μm with rounded knobs; a single anterior outstretched ovary extended toward the base of the esophagus; the developing oocytes existed in two rows, changing to one near the middle of the ovary, and the vulva was thick and elevated, with the posterior uterus extending approximately three-quarters of the distance to the anus; the bursa extended from opposite the anterior end of the spicules approximately three-fourths of the tail length; and the tail was rounded and the lateral field had six incisures. Pathogenicity was tested by inoculating with a 2-ml suspension (approximately 2,000 nematodes) extracted from diseased roots to each of seven intact American ginseng roots. The roots were in a polyethylene bag surrounded by sterile soil and incubated at 25 ± 2°C. On five roots after 60 days, symptoms were similar to those observed in the field, and D. destructor was isolated from the infected parts. The control, inoculated only with sterile water, remained healthy. To our knowledge, this is the first report of D. destructor causing root rot of American ginseng. Reference: (1) G. Thorne. Proc. Helminthol. Soc. Wash. 12:27, 1945.
2004年夏季，在北京地区种植的3年生和4年生西洋参上观察到根腐病，2006年在河北省也发现了这种根腐病。病害初期，根表皮呈浅褐色，有不规则病斑。病斑有时边缘清晰，呈条纹状。在病害后期，根表皮出现裂缝，皮层腐烂，导致其失去商业价值。当根部严重受损时，植株会枯萎。对病根进行植物寄生线虫检测。根据以下特征（1），一种植物寄生线虫被鉴定为毁灭茎线虫：口针长度为9.2至13.3μm，顶端圆钝；单个前伸卵巢向食管基部延伸；发育中的卵母细胞排成两行，在卵巢中部附近变为一行，阴门厚且隆起，后子宫延伸至距肛门约四分之三的距离；交合伞从交合刺前端相对处延伸至尾长的约四分之三；尾端圆钝，侧区有6条侧线。通过将从病根中提取的2毫升悬浮液（约2000条线虫）接种到7株完整的西洋参根上进行致病性测试。根置于装有无菌土壤的聚乙烯袋中，在25±2℃下培养。60天后，5株根上出现了与田间观察到的症状相似的症状，并且从感染部位分离出了毁灭茎线虫。仅接种无菌水的对照植株保持健康。据我们所知，这是关于毁灭茎线虫引起西洋参根腐病的首次报道。参考文献：（1）G. 索恩。《华盛顿蠕虫学协会会刊》12:27，1945年。
