Kalischuk Melanie L, Al-Mughrabi Khalil I, Peters Rick D, Howard Ron J, Platt H W Bud, Kawchuk Lawrence M
Agriculture and Agri-Food Canada, Lethbridge, AB Canada.
NB Department of Agriculture and Aquaculture, Wicklow, NB Canada.
Plant Dis. 2012 Dec;96(12):1729-1735. doi: 10.1094/PDIS-10-11-0859-RE.
A dramatic increase in the incidence of late blight and changes within populations of Phytophthora infestans have been observed in various regions of Canada. In this study, the occurrence of several new genotypes of the pathogen was documented with associated phenotypes that dominated pathogen populations. Genotype US-23, previously detected only among isolates from the United States, dominated in the western Canadian provinces of British Columbia, Alberta (AB), Saskatchewan, and Manitoba (MB). Although isolates of US-23 infect both potato and tomato, these isolates were the only genotype recovered from commercial garden centers in Canada. Isolates of genotype US-8, previously dominant throughout Canada, represented the only genotype detected from the eastern Canadian provinces of New Brunswick and Prince Edward Island. Isolates of other genotypes detected in Canada included US-11 in AB, US-24 in MB, and US-22 in Ontario (ON). An additional genotype was detected in ON which appears to be a derivative of US-22 that may have arisen through sexual reproduction. However, evidence of clonal reproduction dominated among the isolates collected, and opportunities for sexual reproduction were probably limited because of a surprising geographic separation of the A1 and A2 mating types in Canada. Sensitivity of the US-22, US-23, and US-24 isolates to the fungicide metalaxyl, movement of potato seed and transplants, and weather conditions may have contributed to reduced opportunities for contact between the mating types in fields in Canada. All P. infestans isolates were readily distinguished from other related oomycetes with RG57 restriction fragment length polymorphism analysis. Long-distance movement in seed tubers and garden center transplants may have contributed to the rapid spread of the P. infestans genotypes across Canada. Tracking pathogen movement and population composition should improve the ability to predict the genotypes expected each year in different regions of Canada.
在加拿大的不同地区，晚疫病的发病率急剧上升，并且疫霉菌种群也发生了变化。在本研究中，记录了该病原菌几种新基因型的出现以及主导病原菌种群的相关表型。基因型US-23此前仅在美国分离株中被检测到，在加拿大西部省份不列颠哥伦比亚省、艾伯塔省（AB）、萨斯喀彻温省和马尼托巴省（MB）占主导地位。尽管US-23分离株可感染马铃薯和番茄，但这些分离株是加拿大商业园艺中心回收的唯一基因型。基因型US-8的分离株此前在加拿大各地占主导地位，是加拿大东部省份新不伦瑞克省和爱德华王子岛检测到的唯一基因型。在加拿大检测到的其他基因型分离株包括AB省的US-11、MB省的US-24和安大略省（ON）的US-22。在安大略省还检测到另一种基因型，它似乎是US-22的衍生物，可能是通过有性繁殖产生的。然而，在所收集的分离株中，克隆繁殖的证据占主导地位，由于加拿大A1和A2交配型存在惊人的地理隔离，有性繁殖的机会可能有限。US-22、US-23和US-24分离株对杀菌剂甲霜灵的敏感性、马铃薯种薯和移植苗的移动以及天气条件可能导致加拿大田间交配型之间接触的机会减少。通过RG57限制性片段长度多态性分析，所有致病疫霉分离株都能很容易地与其他相关卵菌区分开来。种薯和园艺中心移植苗的远距离移动可能促进了致病疫霉基因型在加拿大的快速传播。追踪病原菌的移动和种群组成应能提高预测加拿大不同地区每年预期基因型的能力。
