高卢蜜环菌群体遗传和地理起源路线研究

Armillaria gallica is the primary symbiotic fungus for Gastrodia elata and Polyporus umbellatus with high economic value. It is, on the other hand, also the severe pathogen of Armillaria root rot that often causes significant economic losses. Traditionally, A. gallica was subdivided into several biological species based on the somatic intersterility. However, somatic fertility was also detected between different biological species in recent studies and the phylogenetic analyses did not support the recognition of these biological species but support treating A. gallica as a genealogically concordant evolutionary population. A. gallica is ubiquitous in North Hemisphere. However, its global genetic structure, affecting factors to population differentiation and the geographical origin routes are still undetermined, which pose negative effects on the pathogen diagnosis, disease control and screening of good symbiotic stains. This project aims to reconstruct the phylogeny using multi-gene sequences from A. gallica samples collected from Eastern Asia, Europe and North America, and that from related species. Divergence time of A. gallica will be estimated based on related fossils era. Genetic distance, gene flow and genetic recombination among continental populations of A. gallica will be analyzed to infer the leading factors to promote the population differentiation and biogeography patterns of all subpopulations. The results from this study are significant for the application of A. gallica in field productions as well as the disease control of Armillaria root rot.

高卢蜜环菌既是中药天麻和猪苓的主要共生菌，具有很高经济价值，又是林木根腐病病原菌，造成严重经济损失。传统上高卢蜜环菌被依据互交不育原则划分为多个生物种，但近期研究发现不同生物种的部分个体之间也存在互交可育现象。此外，系统演化证据并不支持这些生物种的划分，而更支持高卢蜜环菌是一个具有谱系一致性的进化群体。高卢蜜环菌在北半球分布广泛，但其群体遗传结构还不清楚，影响群体分化的因素也不明确，群体的地理起源和进化历史未知，这些问题直接影响了病原诊断、根腐病防治以及生产上优良共生菌种的筛选。本项目拟广泛收集东亚、欧洲及北美的高卢蜜环菌，构建多基因系统演化树，结合化石标定其分化时间，分析各大陆群体间的遗传距离、基因交流和遗传重组，推测驱动群体分化的主导因素和各分化群体间地理起源路线。本项目的研究结果对高卢蜜环菌的生产应用及林木根腐病防治具有重要意义。

蜜环菌属（Armillaria）物种是一类包含重要林木致病菌和菌根菌的一个属，隶属于担子菌纲、伞菌目、膨瑚菌科。目前，该属分布与南北半球的物种分别处于独立的进化分支，北半球物种被很好的聚为三个超支，分别是Mellea超支，Ostoyae超支和Gallica超支，其中Gallica超支是最大的一个，包括7个已经命名的形态种和10个未命名的生物种。但是这些物种间的亲缘关系并不清楚。本研究广泛收集北半球蜜环菌样品，共获得226份，利用多基因构建了北半球蜜环菌系统发育树，并利用GCPSR，PTP和BP&P多种方法划定Gallica超支物种界限，结合PHI检验和前人交配相融事件，显示Gallica超支中仅包含三个物种，分别是A. nabsnona, PS I 和PS II,其中 PS II是一个跨洲分布的大种，曾经被认为的许多形态种或生物种实际为地理分化群体。分子钟显示，Gallica超支起源于中新世(9.1 Mya), 较早形成的北区植物区系可能有利于PS II的跨洲传播和分布。早上新世发生的地理隔离事件，如白令海峡断开以及喜马拉雅的隆升可能是驱动PS II群体分化的重要因素。