Study on vicariance of obligate biotrophs between East Asia and South America

本研究的目的是（1）利用分子系统学分析阐明东亚和南美洲植物专性生物体--白粉病真菌的地理变异的原因;（2）从植物地理学的角度研究白粉病真菌的进化历史。主要结果如下：1）描述了采自阿根廷巴塔哥尼亚的白粉菌属钩壳组一新种。巴塔哥尼亚白粉菌，在Nothofagus x anarctica的叶片上发现，与E. nothofagi和E. kenjiana，但不同之处在于其附属物扭曲整个长度，以及附属物，子囊和子囊孢子的数量。本文报道了白粉菌属（Erysiphe sect. Uncinula）的两个特有种：钩孢白粉菌E. magellanica和E. 2）根据5.8S、18 S和28 S rDNA序列分析，推测了钩丝壳菌在白粉菌目中的系统发育位置。虽然子囊虫的附属物是钩壳 关于我们 与最近引进的基部属Parauncinula ex Uncinula明显不同。钩丝壳在形态上不同于白粉菌组的种。钩丝壳（=钩丝壳）具有顶生、束状（如在三指叉囊壳中）、有隔膜的子囊附属物和Euoidium样无性型（分生孢子链状）。副钩锥虫的附属物也是顶生的，但不是束状的，子囊孢子弯曲，缺乏无性型。森林钩丝壳是一种基部、树栖白粉病，具有一些额外的祖先特征，包括钩丝壳样附属物和6-8孢子子囊。本文提出了新属--盾壳菌属（Caespitotheca），其中C. 3）Golovinomyces是白粉菌科的一个严格的草本寄生属。从分子系统发育分析，最近报道了Golovinomyces属和Asteraceae之间的寄主-寄生虫共种。菊科起源于南美洲，后来将其地理分布扩展到北方半球。如果Golovinomyces与菊科的共生起源于南美洲，则Golovinomyces的地理起源可以假定为南美洲。为了解决这个问题，收集了来自南美洲特有的紫菀族（asteraceous tribe）Mutisieae的宿主的Golovinomyces物种并进行测序。结果表明，分离自Mutisieae的Oidium mutisiae和Golovinomyces leuceriae不属于Golovinomyces树的底部。相反，它们分别位于来自北方半球的Golovinomyces分离物的两个不同进化枝内。因此，Mutisieae族不是Golovinomyces的最早寄主。目前的研究结果表明，Golovinomyces起源于北方半球，而不是在南美洲

The aims of this study were (1) to clarify the causal factors of vicariance of powdery mildew fungi, obligate biotrophs of plants, between East Asia and South America using molecular phylogenetic analyses, and (2) to study evolutional history of the powdery mildew fungi from the view of biogeography. The main results are described below,1) A new species of Erysiphe sect. Uncinula is described and illustrated from Patagonia, Argentina. Erysiphe patagoniaca sp. nov., found on leaves of Nothofagus x antarctica, is similar to E. nothofagi and E. kenjiana, but differs in its appendages twisted throughout the length, and number of appendages, asci and ascospores. The two endemic species of Erysiphe sect. Uncinula, E. magellanica and E. nothofagi, coexisted on the same leaves together with Erysiphe patagoniaca.2) The phylogenetic position of Uncinula forestalls within the Erysiphales has been inferred from 5.8S, 18S, and 28S rDNA sequences. Although the appendages of the ascomata are Uncinula … More -like and clearly separate from the recently introduced basal genus Parauncinula ex Uncinula. Uncinula forestalls differs morphologically from the species of Erysiphe sect. Uncinula (= Uncinula) in having terminal, fasciculate (as in Podosphaera tridactyla), septate ascoma appendages and a Euoidium-like anamorph (conidia catenate). In Parauncinula, the appendages are also terminal but not fasciculate, the ascospores are curved, and the anamorph is lacking. Uncinula forestalis is a basal, tree-inhabiting powdery mildew with some additional ancestral characteristics, including Uncinula-like appendages and 6-8-spored asci. The new genus Caespitotheca is proposed, with C. forestalis as the type species.3) Golovinomyces is a strictly herb-parasitic genus in the Erysiphaceae. Host-parasite co-speciation was reported recently between the genus Golovinomyces and Asteraceae from molecular phylogenetic analyses. The Asteraceae originated in South America and latterly expanded their geographic distribution into the Northern Hemisphere. If the co-speciation between Golovinomyces and Asteraceae originated in South America, the geographic origin of Golovinomyces could be assumed to be South America. To address this question, Golovinomyces species from hosts of the tribe Mutisieae, an asteraceous tribe endemic to South America, were collected and sequenced. Results indicate that Oidium mutisiae and Golovinomyces leuceriae isolated from the Mutisieae do not belong at the base of the Golovinomyces tree. Instead, they are situated separately within two different clades of Golovinomyces isolates from the Northern Hemisphere. Therefore, the tribe Mutisieae is not the most early host of Golovinomyces. Present results suggest that Golovinomyces originated in the Northern Hemisphere, and not in South America Less