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

本研究的目的是：(1)利用分子系统发育分析方法阐明植物专性生物营养物白粉病真菌在东亚和南美之间变异的原因；(2)从生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)在阿根廷巴塔哥尼亚描述了一新种Erysiphe sect. Uncinula。发现于南极Nothofagus x antarctica叶片上的Erysiphe patagoniaca sp. nov.与nothofagi和kenjiana相似，但其附属物的长度、附属物的数量、附属物的子囊和子囊孢子的数量不同。麦哲伦赤霉（E. magellanica）和nothofagi赤霉（E. nothofagi）与巴塔哥尼亚赤霉（Erysiphe patagoniaca）在同一叶片上共存。2)从5.8S、18S和28S rDNA序列中推断出了钩环蕨在丹参科中的系统发育位置。虽然附属物是带环的，但更像，并且与最近引入的基属Parauncinula ex Uncinula明显分开。在形态上不同于丹参科的一种。丹参（=丹参）具有顶生，束状（如在三叉足足），分离的体表附属物和一类似于紫菀的畸形（分生孢子链状）。副子囊的附属物也是顶生的，但不是束状的，子囊孢子弯曲，没有变形。森林卷带菌是一种基生的，栖息在树上的白粉病，具有一些额外的祖先特征，包括卷带样附属物和6-8孢子的囊。提出了新属Caespitotheca，以C. forestalis为模式种。Golovinomyces是丹参科中一个严格意义上的草本寄生属。从分子系统发育的角度分析了菊科和戈洛维菌属的宿主-寄生虫共种现象。菊科起源于南美洲，后来将其地理分布扩展到北半球。如果Golovinomyces与Asteraceae的共种形成起源于南美洲，那么Golovinomyces的地理起源可以假定为南美洲。为了解决这个问题，我们收集了来自南美洲特有的星形部落mutisiae宿主的Golovinomyces物种并进行了测序。结果表明，从该菌中分离出的多芽黄菌（Oidium mutisiae）和绿芽黄菌（Golovinomyces leuceriae）不属于绿芽黄菌树的底部。相反，它们分别位于北半球戈洛维菌分离株的两个不同分支中。因此，mutisiae部落并不是戈洛维菌最早期的宿主。目前的研究结果表明，戈洛维菌属起源于北半球，而不是南美洲

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