Abstract
We isolated and analyzed entomopathogenic microsporidia from the common cutworm, which were surveyed in vegetable crop fields on Chichijima, Ogasawara Islands, Japan, from April 2012 to March 2014. The infection rate of of the Spodoptera litura by microsporidia was 3.54% (161 of the 4,544 surveyed S. litura adults). In addition, 10 discrete strains of microsporidia collected from infected adults were measured for spore size and analyzed at the molecular level.
Analysis of the spore sizes indicated that the 10 strains of microsporidia isolated from the Ogasawara Islands comprised several different genera. Furthermore, analysis of the small-subunit ribosomal RNA sequences revealed that several microsporidian strains isolated from S. litura were closely related to Nosema bombycis from the silkworm Bombyx mori. Other microsporidia belonged to the Pleistophora and Trachipleistophora clusters. Therefore, the Ogasawara strains did not form a single genus group but were classified into at least 3 groups. This is the first study to identify the genus Trachipleistophora in lepidopteran insects in Japan. These results suggest that the microsporidia isolated from S. litura in the Ogasawara islands are genetically diverse.
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