Iglesias-Garcia Angela M, Villarroel-Zeballos Maria I, Feng Chunda, Toit Lindsey J du, Correll James C
Department of Plant Pathology, University of Arkansas, Fayetteville 72701.
Department of Plant Pathology, Washington State University Mount Vernon NWREC, Mount Vernon 98273.
Plant Dis. 2013 Nov;97(11):1457-1469. doi: 10.1094/PDIS-01-13-0016-RE.
In 2005, Verticillium dahliae was first reported to be pathogenic to spinach seed crops in the Pacific Northwest, with symptoms only developing after initiation of the reproductive stage of plant growth, and to be prevalent on commercial spinach seed lots produced in Denmark, The Netherlands, and the United States. In this study, the genetic diversity, pathogenicity, and virulence were examined for a collection of isolates of Verticillium spp. from spinach as well as other hosts (alfalfa, cotton, lettuce, mint, peppermint, potato, radish, and tomato) from various countries and from different vegetative compatibility groups (VCGs). Of a total of 210 isolates of V. dahliae obtained from spinach seed produced in Denmark, the Netherlands, New Zealand, or the United States, 128 were assigned to VCG 4B (89% of 91 U.S. isolates, 86% of 42 isolates from the Netherlands, 19% of 43 Denmark isolates, and 8% of 13 New Zealand isolates), 65 to VCG 2B (92% of the New Zealand isolates, 79% of the Denmark isolates, 14% of the Netherlands isolates, and 9% of the U.S. isolates), and 3 to VCG 2A (2% of each of the Denmark and U.S. isolates, and 0% of the Netherlands and New Zealand isolates); 14 isolates could not be assigned to a VCG. Although little variation in the sequence of the internal transcribed spacer (ITS) region of ribosomal DNA was observed among isolates within each Verticillium sp., the ITS region readily differentiated isolates of the species V. dahliae, V. tricorpus, and Gibellulopsis nigrescens (formerly V. nigrescens) obtained from spinach seed. Greenhouse pathogenicity assays on spinach, cotton, lettuce, and tomato plants using isolates of V. dahliae (n = 29 to 34 isolates), V. tricorpus (n = 3), G. nigrescens (n = 2), and V. albo-atrum (n = 1) originally obtained from these hosts as well as from alfalfa, mint, peppermint, potato, and radish, revealed a wide range in virulence among the isolates. Isolates of V. tricorpus and G. nigrescens recovered from spinach seed and an isolate of V. albo-atrum from alfalfa were not pathogenic on spinach. In addition, isolates of V. dahliae from mint and peppermint were not pathogenic or only weakly virulent on the hosts evaluated. Although there was a wide range in virulence among the isolates of V. dahliae tested, all of the V. dahliae isolates caused Verticillium wilt symptoms on spinach, lettuce, tomato, and cotton. None of the isolates of V. dahliae showed host specificity. These results indicate that Verticillium and related species associated with spinach seed display substantial variability in virulence and pathogenicity to spinach and other plants but the V. dahliae isolates were restricted to three VCGs.
2005年，首次报道大丽轮枝菌对太平洋西北地区的菠菜种子作物具有致病性，症状仅在植物生长进入生殖阶段后才出现，并且在丹麦、荷兰和美国生产的商业菠菜种子批次中普遍存在。在本研究中，对从菠菜以及来自不同国家和不同营养亲和群（VCG）的其他寄主（苜蓿、棉花、生菜、薄荷、胡椒薄荷、马铃薯、萝卜和番茄）中分离得到的轮枝菌属菌株的遗传多样性、致病性和毒力进行了检测。从丹麦、荷兰、新西兰或美国生产的菠菜种子中获得的总共210株大丽轮枝菌分离株中，128株被归为VCG 4B（91株美国分离株中的89%，42株荷兰分离株中的86%，43株丹麦分离株中的19%，13株新西兰分离株中的8%），65株归为VCG 2B（92%的新西兰分离株，79%的丹麦分离株，14%的荷兰分离株，9%的美国分离株），3株归为VCG 2A（丹麦和美国分离株各占2%，荷兰和新西兰分离株占0%）；14株分离株无法归为某个VCG。尽管在每个轮枝菌属物种内的分离株之间，核糖体DNA的内部转录间隔区（ITS）序列几乎没有变化，但ITS区域很容易区分从菠菜种子中获得的大丽轮枝菌、三叉轮枝菌和变黑拟盘多毛孢（原黑轮枝菌）的分离株。使用最初从这些寄主以及苜蓿、薄荷、胡椒薄荷、马铃薯和萝卜中获得的大丽轮枝菌（n = 29至34株分离株）、三叉轮枝菌（n = 3株）、变黑拟盘多毛孢（n = 2株）和黑白轮枝菌（n = 1株）分离株，对菠菜、棉花、生菜和番茄植株进行温室致病性测定，结果显示分离株之间的毒力差异很大。从菠菜种子中分离得到的三叉轮枝菌和变黑拟盘多毛孢分离株以及从苜蓿中分离得到的黑白轮枝菌分离株对菠菜无致病性。此外，从薄荷和胡椒薄荷中分离得到的大丽轮枝菌分离株对所评估的寄主无致病性或仅具有弱毒力。尽管在所测试的大丽轮枝菌分离株中毒力差异很大，但所有大丽轮枝菌分离株均在菠菜、生菜、番茄和棉花上引起了黄萎病症状。没有一株大丽轮枝菌分离株表现出寄主特异性。这些结果表明，与菠菜种子相关的轮枝菌属及相关物种对菠菜和其他植物的毒力和致病性存在很大差异，但大丽轮枝菌分离株仅限于三个VCG。
