Antonopoulos Dimitrios F, Melton Thomas, Mila Asimina L
Department of Plant Pathology, North Carolina State University, Raleigh 27695.
Plant Dis. 2010 May;94(5):613-620. doi: 10.1094/PDIS-94-5-0613.
Black shank, caused by the hemibiotrophic oomycete Phytophthora parasitica var. nicotianae, is a major disease of tobacco (Nicotiana tabacum). The rise of race 1 in the late 1990s, after extensive cropping of cultivars possessing the Php gene, confirming immunity to race 0 of P. parasitica var. nicotianae, imposed new challenges to black shank management. The effects of tobacco cultivars and chemical controls with mefenoxam (Ridomil Gold) on black shank incidence were investigated in naturally infested fields. Twenty-five cultivars were tested and the highest resistance for races 0 and 1 of P. parasitica var. nicotianae was provided by RJR 75 and SP 227 based on field and laboratory studies. When race 1 was prevalent, mefenoxam was effective to control black shank. An initial application at an early stage of tobacco growth, such as a few days before or after transplant, was essential to successfully control the disease. In greenhouse experiments, cultivars carrying the Php gene produced fewer and shorter adventitious roots than cultivars possessing only partial resistance to all races of P. parasitica var. nicotianae. Strategies such as use of mefenoxam, especially at an early stage, when adventitious roots are emerging, and planting a cultivar with high partial resistance or possessing the Ph gene when race 1 or race 0, respectively, predominates are critical factors in reducing loss due to P. parasitica var. nicotianae.
黑胫病由半活体营养型卵菌烟草疫霉寄生变种引起，是烟草（Nicotiana tabacum）的一种主要病害。20世纪90年代后期，在广泛种植具有Php基因、对烟草疫霉寄生变种0号生理小种具有免疫性的品种之后，1号生理小种的出现给黑胫病防治带来了新挑战。在自然发病的田块中，研究了烟草品种和使用甲霜灵（瑞毒霉锰锌）进行化学防治对黑胫病发病率的影响。测试了25个品种，根据田间和实验室研究结果，RJR 75和SP 227对烟草疫霉寄生变种0号和1号生理小种表现出最高抗性。当1号生理小种流行时，甲霜灵对防治黑胫病有效。在烟草生长早期，如移栽前或移栽后几天进行首次施药，对于成功防治该病至关重要。在温室试验中，携带Php基因的品种比仅对烟草疫霉寄生变种所有生理小种具有部分抗性的品种产生的不定根更少且更短。使用甲霜灵的策略，尤其是在不定根出现的早期阶段，以及在1号或0号生理小种分别占主导时种植具有高部分抗性或携带Ph基因的品种，是减少烟草疫霉寄生变种造成损失的关键因素。
