Analysis of host exponsion sorategy of the Erysiphales using moleculor phylogenetic techniques

1.基于核糖体DNA核苷酸序列的系统发育分析表明，白粉菌可分为五个主要谱系。分生孢子期的形态可以很好地确定各自的谱系，而子囊期的形态则不能很好地描述它们的谱系。在这个真菌群中，树木寄生的类群通常是祖先的，并且在各自的谱系内发生了多次从树木到草本植物的寄主扩展。随着寄主向草本植物的扩展，附属物的形态发生了多次简化。因此，简单的菌丝状附属物是会聚的结果。对囊虫族的寄主扩展途径进行了详细的研究。Sphaerotheca属的两个组分别起源于Podosphaera属。木兰组是由寄生于李属(蔷薇科)的Podosphaera种派生而来，经获得寄生于玄参科后，又将寄主范围扩大到菊科。在…上进行遗传辐射后更多的是菊科植物，它们进一步将寄主范围扩大到其他植物科。根据Berbee和Taylor(2001)报道的分子时钟(1.26%/100 MYR)，计算出白粉菌目和粘毛菌科的分裂和白粉菌目内的第一次分歧分别发生在100和76 MYR之前。2.在本研究分析的Golovinmyces分类群中，鉴定出五个主要类群，每个主要类群由来自菊科一个部落的菌株代表。4组寄主植物均严格限制为菊科植物。第5个类群，即Lactuceae群，是从菊科Lactuceae部落和所有其他植物科中收集的菌株组成的一个大群，这表明Golovinmyces在进化的早期阶段与Asteraceae有着密切的亲缘关系。我们认为，黄曲霉寄主-寄生关系的进化史有两个不同的阶段。一个阶段是与寄主的系统发育相一致的分化，这种分化发生在菊科内。另一个阶段是从菊科到其他科和菊科内部的寄主跳跃。较少

1.Phylogenetic analyses based on the nucleotide sequences of the nuclear ribosomal DMA revealed that the powdery mildew fungi are divided into five major lineages. The respective lineage was well defined by the morphology of conidial stage, but not of ascomata. In this fungal group, tree-parasitic taxa are generally ancestral, and multiple times of host expansion from trees to herbs have occurred within the respective lineage. Accompanying with the host expansion to herbs, simplification of appendage morphology has occurred multiple times. The simple, mycelioid appendages are thus a result of convergence. Host expansion route was investigated in detail in the tribe Cystotheceae. Two sections of the genus Sphaerotheca were derived from the genus Podosphaera separately. The section Magnicellulatae was derived from a Podosphaera species parasitic to Prunus (Rosaceae), acquired parasitism to the Scrophulariaceae, and then expanded host range into the Asteraceae. After genetic radiation on … More the Asteraceae, they further expanded their host ranges into other plant families. According to the molecular clock (1.26%/100 myr) reported by Berbee and Taylor (2001), splitting of the Erysiphales and the Myxotrichaceae and first divergence within the Erysiphales was calculated to have occurred 100 and 76 myr ago, respectively.2.Five major groups, each represented by isolates from a single tribe of the Asteraceae, were identified in Golovinomyces taxa analyzed in this study. Host plants of four groups were strictly restricted to the Asteraceae. The fifth group, the Lactuceae group, is a large group composed of isolates collected from the tribe Lactuceae of the Asteraceae and all other plant families, which suggests a close affinity between Golovinomyces and the Asteraceae in the early stages of their evolution. We suggest that there are two different phases in the evolutionary history of the host-parasite relationships of Golovinomyces. One phase is divergence in accord with the phytogeny of their hosts, which occurred within the Asteraceae. The another phase is host-jumping, which occurred from the Asteraceae to other families and within the Asteraceae. Less