Journal of Microbiology

Research Support, Non-U.S. Gov'ts

NOTE] Mitochondrial Phylogeny Reveals Intraspecific Variation in Peronospora effusa, the Spinach Downy Mildew Pathogen: Young-Joon Choi , Marco Thines , Jae-Gu Han , Hyeon-Dong Shin; J. Microbiol. 2011;49(6):1039-1043. Published online December 28, 2011; DOI: https://doi.org/10.1007/s12275-011-1069-2

Abstract: Since about two hundred years, downy mildew caused by Peronospora effusa is probably the most economically important disease of spinach (Spinacia oleracea). However, there is no information on the global phylogeographic structure of the pathogen and thus it is unclear whether a single genotype occurs worldwide
or whether some local genetic variation exists. To investigate the genetic variability of this pathogen, a sequence analysis of two partial mitochondrial DNA genes, cox2 and nad1, was carried out. Thirty-three specimens of Peronospora effusa from four continents were analyzed, including samples from Australia, China, Japan, Korea, Mexico, Russia, Sweden, and the USA. Despite the potential anthropogenic admixture of genotypes, a phylogeographic pattern was observed, which corresponds to two major groups, an Asian/Oceanian clade and another group, which includes American/European specimens. Notably, two of six Japanese specimens investigated did not belong to the Asian/Oceanian clade, but were identical to three of the specimens from the USA, suggestive of a recent introduction from the USA to Japan. As similar introduction events may be occurring as a result of the globalised trade with plant and seed material, a better knowledge of the phylogeographic distribution of pathogens is highly warranted for food security purposes.

Genetic Variation and Geographic Distribution of Megalocytiviruses: Jun-Young Song , Shin-Ichi Kitamura , Sung-Ju Jung , Toshiaki Miyadai , Shinji Tanaka , Yutaka Fukuda , Seok-Ryel Kim , Myung-Joo Oh; J. Microbiol. 2008;46(1):29-33.; DOI: https://doi.org/10.1007/s12275-007-0184-6

Abstract: Viruses belonging to the genus Megalocytivirus in the family Iridoviridae have caused mass mortalities in marine and freshwater fish in Asian countries. In this study, partial major capsid protein (MCP) gene of seven Japanese and six Korean megalocytiviruses was sequenced and compared with the known megalocytiviruses to evaluate genetic variation and geographic distribution of the viruses. Comparison of MCP gene nucleotide sequences revealed sequence identity of 92.8% or greater among these 48 isolates. A phylogenetic tree clearly revealed three clusters: genotype I including nine Japanese isolates, thirteen Korean isolates, one Chinese isolates, one Thailand isolate and one South China Sea isolate; genotype II including five freshwater fish isolates in Southeast Asian countries and Australia; and the remaining genotype III mainly consisted of flatfish isolate in Korea and China. This suggests that viruses belonging to the genotype I widely distribute among various fish species in many Asian countries. Conversely, the epidemic viruses belonged to genotype II and III are may be still locally spreading and constrained in their prevalence to the limited host fish species, i.e., genotype II viruses mainly distribute in Southeast Asian countries, whereas genotype III viruses distribute in flatfish species in Korea and China.

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