Genus Golovinomyces Research Articles

Morphological and molecular characterization of Oidium subgenus Reticuloidium (powdery mildew) newly occurred on cucumber in Japan

In 2002, a powdery mildew with catenate conidia lacking fibrosin bodies was found on cucumber in a greenhouse in Kanagawa Prefecture, Japan. Morphological observation revealed that the fungus belongs to Oidium subgenus Reticuloidium, anamorph of the genus Golovinomyces. Molecular phylogenetic analyses of the nucleotide sequences of the rDNA ITS regions and D1/D2 domains of the 28S rDNA indicated that the fungus belongs to the clade of G. orontii with other Golovinomyces fungi from a wide range of host plants, suggesting that the fungus was newly transported from abroad. Because there has been no prior report of cucumber powdery mildew caused by Reticuloidium, further research on the physiology, epidemiology, control and resistant cucumber varieties is required.

Molecular phylogeny supports a Northern Hemisphere origin of Golovinomyces ( Ascomycota: Erysiphales)

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 the ITS and 28S rDNA regions 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. The new species Oidium reginae for the previous O. mutisiae on Mutisia decurrens is proposed.

Molecular identification ofGolovinomyces(Ascomycota: Erysiphales) anamorphs on the Solanaceae in Australia

Three taxa of anamorphic powdery mildews (Erysiphales: Ascomycota), referable to the teleomorph genus Golovinomyces on the Solanaceae in Australia, were determined by the RFLP analysis and sequencing of the rDNA ITS region. The first taxon, part of an Oidium lycopersici-O. longipes clade, occurred on a range of host genera including Solanum, Cyphomandra, Lycopersicon, Nicotiana and Petunia. The second taxon consisted of specimens on Solanum tuberosum and Cestrum and was referable to the Golovinomyces orontii complex. The third taxon contained a single specimen from glasshouse grown Lycopersicon esculentum and is suspected to be G. biocellatus, a species previously known only from the Lamiaceae.

Evolution of host–parasite relationships of Golovinomyces (Ascomycete: Erysiphaceae) inferred from nuclear rDNA sequences

To understand the evolution of host–parasite relationships in the genus Golovinomyces (Ascomycete: Erysiphaceae), which are obligate parasitic fungi of plants, we investigated the phylogenetic relationships of the genus based on 60 internal transcribed spacer (ITS) and 41 28S rDNA sequences. Five major groups, each represented by isolates from a single tribe of the Asteraceae, were identified in the 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. Tree topology comparisons between the asteraceous hosts and their parasites suggest that Golovinomyces diverged along with the phylogeny of host tribes Carsueae, Astereae, Heliantheae, and Lactuceae of the Asteraceae. However, a conflict of branching order between the tribe Anthemideae and their parasites suggests that host-jumping has occurred in the tribe Anthemideae. Consequently, 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 phylogeny 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.