Sullivan M J, Melton T A, Shew H D
National Weed Management Laboratory, United States Department of Agriculture APHIS PPQ CPHST, Fort Collins, CO 80526.
Associate State Program Leader, AgNR/CRD, Cooperative Extension Service, North Carolina State University, Raleigh 27695-7602.
Plant Dis. 2005 Dec;89(12):1285-1294. doi: 10.1094/PD-89-1285.
Deployment of tobacco cultivars with single-gene, complete resistance to race 0 of the tobacco black shank pathogen, Phytophthora parasitica var. nicotianae, has resulted in a rapid increase in the occurrence of race 1 of the pathogen in North Carolina. Cultivar-rotation studies were conducted in three fields to assess how different levels and types of resistance affected the race structure and population dynamics of the pathogen when deployed in fields initially containing single or mixed races of the pathogen. In a field with both races present, a high level of partial resistance in cv. K 346 was most effective in reducing disease and decreasing the proportion of race 1 in the pathogen population. The deployment of complete resistance in cv. NC 71 resulted in intermediate levels of disease control and race 1 became the predominate race. The cv. K 326, with a low level of partial resistance, had the highest levels of disease, and race 0 was the dominant race recovered. In a field where no race 1 was detected initially, disease incidence was high with the use of partial resistance. Complete resistance was very effective in suppressing disease, but race 1 was recovered after only one growing season. By the end of the third growing season, race 1 was recovered from most treatments where single-gene resistance was deployed. A high level of partial resistance was most effective in suppressing disease in a field where race 1 initially was the predominant race. A rotation between cultivars with single-gene resistance and cultivars with a high level of partial resistance should provide the most effective approach to black shank management. This rotation will reduce disease incidence and minimize race shifts in the pathogen and, over time, should prolong the usefulness of the Ph gene for black shank control in commercial production of tobacco.
部署对烟草黑胫病病原菌寄生疫霉变种0号生理小种具有单基因完全抗性的烟草品种，已导致北卡罗来纳州该病原菌1号生理小种的发生率迅速上升。在三块田地里进行了品种轮作研究，以评估不同水平和类型的抗性在最初含有该病原菌单一或混合生理小种的田地里部署时，对病原菌的生理小种结构和种群动态有何影响。在一块同时存在两个生理小种的田地里，K 346品种的高水平部分抗性在减轻病害和降低病原菌种群中1号生理小种的比例方面最为有效。NC 71品种中完全抗性的部署导致了中等水平的病害控制，1号生理小种成为优势生理小种。具有低水平部分抗性的K 326品种病害水平最高，回收的优势生理小种是0号。在一块最初未检测到1号生理小种的田地里，使用部分抗性时病害发生率很高。完全抗性在抑制病害方面非常有效，但仅一个生长季节后就出现了1号生理小种。到第三个生长季节结束时，在大多数部署了单基因抗性的处理中都回收了1号生理小种。在一块最初1号生理小种占优势的田地里，高水平部分抗性在抑制病害方面最为有效。具有单基因抗性的品种和具有高水平部分抗性的品种之间的轮作应该是防治烟草黑胫病最有效的方法。这种轮作将降低病害发生率，并使病原菌的生理小种变化最小化，随着时间的推移，应该会延长Ph基因在烟草商业生产中防治黑胫病的有效性。
