Yakabe L E, Parker S R, Kluepfel D A
United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, CA 95616.
Plant Dis. 2012 Oct;96(10):1415-1421. doi: 10.1094/PDIS-05-11-0364-RE.
Greater than 75% of English walnut production in the United States occurs on the walnut rootstock Juglans hindsii × J. regia 'Paradox', which is highly susceptible to infection by Agrobacterium tumefaciens. When seed were germinated and grown in the presence of A. tumefaciens, in the absence of wounding, 94% of the seedlings exhibited tumors while 89% contained systemic A. tumefaciens populations. When seedlings were wound inoculated, A. tumefaciens established endophytic populations in stem tissue and often migrated from the site of infection. Distribution of A. tumefaciens in the stem was random and may exhibit seasonal variation. A. tumefaciens populations in root tissue were more readily detected than in stem tissue and may serve as a reservoir for subsequent infection of the aerial portions of the tree. Importantly, 7% of inoculated, asymptomatic seedlings contained endophytic populations of A. tumefaciens. In all, 17% of seedlings inoculated as seeds developed galls at secondary stem-wound sites. These results provide an ecological and epidemiological foundation upon which to modify existing tree-handling practices in both nursery and orchard production environments to manage crown gall incidence.
美国超过75%的英国核桃产量来自核桃砧木加州黑核桃×核桃‘Paradox’，这种砧木极易受到根癌土壤杆菌的感染。当种子在根癌土壤杆菌存在的情况下萌发并生长，且没有伤口时，94%的幼苗出现肿瘤，89%的幼苗含有系统性根癌土壤杆菌种群。当对幼苗进行伤口接种时，根癌土壤杆菌在茎组织中建立内生种群，并经常从感染部位迁移。根癌土壤杆菌在茎中的分布是随机的，可能存在季节性变化。与茎组织相比，根组织中的根癌土壤杆菌种群更容易被检测到，并且可能成为随后感染树体地上部分的菌源库。重要的是，7%接种后无症状的幼苗含有根癌土壤杆菌内生种群。总体而言，作为种子接种的幼苗中有17%在次生茎伤口部位形成了瘿瘤。这些结果为在苗圃和果园生产环境中修改现有树木处理方法以控制冠瘿发病率提供了生态和流行病学基础。
