Dorrance A E, Inglis D A, Derie M L, Brown C R, Goodwin S B, Fry W E, Deahl K L
Department of Plant Pathology, The Ohio State University, Wooster 44691.
Washington State University, Mount Vernon-Research and Extension Unit, 16650 State Route 536, Mount Vernon 98273-9761.
Plant Dis. 1999 May;83(5):423-428. doi: 10.1094/PDIS.1999.83.5.423.
The first detection in the United States of isolates of Phytophthora infestans having metalaxyl insensitivity and complex pathotypes occurred in western Washington during the early 1990s. To determine the genetic structure of the current population in western Washington, a total of 115 isolates of P. infestans were obtained during 1996 from infected tubers or foliage of potato, tomato, nightshade, and bittersweet throughout the region. An additional 45 isolates were collected from a single field. Based on mating type, metalaxyl-insensitivity, and molecular markers (allozymes of glucose-6-phosphate isomerase, peptidase, and RG57 DNA fingerprint), all of the isolates were A1 mating type and had the US-11 multilocus genotype. Analyses of an additional 120 isolates collected during 1997 from potato, tomato, and nightshade were performed. As in 1996, US-11 was the predominant genotype detected on all three hosts. However, three additional A2 mating type genotypes were also detected: US-7, US-8, and US-14. These three genotypes represent the first A2 mating type isolates detected in western Washington. Most of a subset of 60 isolates infected 4 to 7 of the 10 potato differentials tested. This included 90% of the isolates collected in 1996 (all US-11), plus 72% of the US-11 and 100% of the US-8 and US-14 isolates collected during 1997. Virulence phenotypes in this region are complex even without the selection pressure of R-genes in the local commercial cultivars. The apparent increase in genetic variation observed in populations of P. infestans in western Washington from 1996 to 1997 most likely occurred by migration rather than by sexual recombination.
20世纪90年代初，美国华盛顿州西部首次检测到对甲霜灵不敏感且具有复杂致病型的致病疫霉分离株。为了确定华盛顿州西部当前种群的遗传结构，1996年从该地区感染的马铃薯、番茄、茄属植物和苦甜茄的块茎或叶片中总共获得了115株致病疫霉分离株。另外45株分离株从一块田地中采集。基于交配型、对甲霜灵的不敏感性和分子标记（葡萄糖-6-磷酸异构酶、肽酶的同工酶以及RG57 DNA指纹），所有分离株均为A1交配型且具有US-11多位点基因型。对1997年从马铃薯、番茄和茄属植物中采集的另外120株分离株进行了分析。与1996年一样，US-11是在所有三种寄主上检测到的主要基因型。然而，还检测到另外三种A2交配型基因型：US-7、US-8和US-14。这三种基因型代表了在华盛顿州西部首次检测到的A2交配型分离株。60株分离株的一个子集大部分感染了所测试的10个马铃薯鉴别品种中的4至7个。这包括1996年收集的90%的分离株（均为US-11），加上1997年收集的72%的US-11分离株以及100%的US-8和US-14分离株。即使没有当地商业品种中R基因的选择压力，该地区的毒力表型也很复杂。1996年至1997年华盛顿州西部致病疫霉种群中观察到的遗传变异明显增加，最有可能是通过迁移而非有性重组发生的。
