云南致病疫霉交配型、甲霜灵敏感性、mtDNA单倍型及其群体演替研究

Characteristics of Mating Type,Metalaxyl Sensitivity,mtDNA Haplotype and Succession of Phytophthora infestans Populations in Yunnan,2000 to 2003

【目的】对致病疫霉群体特征的认识,是控制晚疫病危害的必要前提。【方法】对云南32个马铃薯和番茄产区的致病疫霉群体的交配型、甲霜灵敏感性、mtDNA单倍型进行了研究。【结果】云南马铃薯致病疫霉群体主要由A1交配型组成,番茄致病疫霉全部为A1交配型。A2交配型和自育型菌株总体发生频率较低,分别为3.4%和4.4%。自从2002年以后,致病疫霉的群体结构发生了明显的变化,没有检测到A2交配型或自育型菌株。致病疫霉对甲霜灵敏感性的离体测定显示马铃薯和番茄上均存在抗性、中抗和敏感菌株。甲霜灵抗性、中抗、敏感菌株分别占测定菌株的13.2%、9.4%和77.4%。分离自番茄的甲霜灵抗性菌株比例高于分离自马铃薯的菌株。Ⅰa、Ⅱa和Ⅰb三种mtDNA单倍型被检测到,马铃薯致病疫霉有Ⅰa和Ⅱa两种单倍型,全部为第二次全球迁移后出现的“新”群体。Ⅰa单倍型在群体中的比例为96%,分布于所有马铃薯产区;番茄致病疫霉则为Ⅰa和Ⅰb两种单倍型,“新”、“旧”群体共存。【结论】马铃薯和番茄致病疫霉群体的遗传结构有明显差异;致病疫霉“新”、“旧”群体在云南已发生演替,马铃薯致病疫霉“新”群体已成功替代了“旧”群体;迁移和有限的有性生殖可能在云南致病疫霉群体的演替中担当了重要的作用。

[Objective] The study was necessary to manage the late blight disease and to characterize populations of Phytophthora infestans. [Method] The characteristics of mating type, metalaxyl sensitivity and mtDNA haplotype of P. infestans isolates were collected from 32 potato and tomato production regions in Yunnan and were analyzed. [Result] Most isolates from potato and all isolates from tomato were A1 mating type. Frequency of A2 mating type and self-fertility isolates were 3.4% and 4.4% respectively. They were only detected in four potato regions. The population structure of P. infestans had changed dramatically and A2 or self-fertility isolates had not been detected in Yunnan since 2002. In vitro tests of sensitivity to the phenylamide fungicide metalaxyl showed that resistant, intermediate and sensitive isolates occurred on potato and tomato with the frequency 13.2%, 9.4% and 77.4% respectively. The frequency of resistance to metalaxyl was higher in isolates from tomato than in isolates from potato. Three mtDNA haplotypes Ⅰ a, Ⅱ a and Ⅰ b were detected from P. infestans populations on potato and tomato in Yunnan. Both Ⅰ a and Ⅱ a haplotypes of P. infestans from potato belonged to the ‘new＇ populations that followed the second global migration of the pathogen. The frequency of Ⅰ a haplotype was 96%, spreading all potato production regions. Isolates from tomato belonged to Ⅰ a and Ⅰ b haplotypes and showed that the ＂old＂ and ＂new＂ populations of P.infestans coexisted in Yunnan. [Conclusion] There was obvious difference between populations of P. infestans from potato and tomato. The succession between ＂old＂ and ＂new＂ P. infestans populations had already occurred and the ＂new＂ populations had successfully replaced the ＂old＂ population on potato. Migration and limited sexual reproduction might play an important role on variation and replacement of P. infestans populations in Yunnan.