不同分离方法获得的冬虫夏草无性型菌株的交配型 基因MAT1-2-1的初步分析

对采用不同分离方法获得的40个冬虫夏草（Ophiocordyceps sinensis）无性型菌株进行交配型基因MAT1-2-1的PCR特异扩增,并随机取其中7个拼接好的MAT1-2-1的碱基序列,与4个来自GenBank 数据在内的共11个样品构建了系统发育树。结果表明,采自青海的7个供试菌株,连同GenBank中来自青海的菌株（FJ654176）共同组成了一大类群,而GenBank中其他地区的菌株则聚成另外的类群;随机分离得到的10个单子囊孢子菌株全部含有MAT1-2-1基因, MAT1-1: MAT1-2未见按4:4进行分离,提示冬虫夏草极有可能是同宗配型。     

Monitoring virulence and sexual compatibility in Brazilian Bremia lactucae populations

During the winter, there is a high occurrence of downy mildew on lettuce caused by Bremia lactucae. This oomycete shows variability in virulence, so understanding the genetic structure of the pathogen population becomes essential for obtaining resistant cultivars. Thus, the objective of this study was to determine sexual compatibility in Brazilian populations of B. lactucae and investigate the occurrence of sexual reproduction of the pathogen on lettuce (Lactuca sativa) and prickly lettuce (Lactuca serriola). Leaf samples were collected in 33 municipalities in seven Brazilian states. The virulence structure of the populations was monitored using the EU-C sextet code. B. lactucae populations from the states of São Paulo, Paraná, Rio de Janeiro, and Rio Grande do Sul shared six of the 15 virulence factors evaluated. Twenty-five virulence phenotypes (v-phenotypes) were found, with the sextet codes 31-00-02, 31-16-02, 31-24-02, and 31-01-02 being more frequent. The predominance of some v- phenotypes indicates that clonal reproduction is still the main form of B. lactucae propagation. The genes and resistance factors of the cultivars Argelès (Dm38), Balesta, and Bartoli are recommended as suitable sources of lettuce resistance in Brazil. Natural occurrence of oospores was detected in most sampled locations, in lettuce and prickly lettuce plants. Virulence variability of Brazilian isolates is the result of the pathogen's ability to reproduce both sexually and asexually, with a prevalence of homothallic isolates; although the majority were of the predominant B₂ mating type, there was a high incidence of predominant B₁ in addition to B₁ = B₂.