Mode of transmission and morphological structures of two Eremothecium species between Riptortus pedestris and soybean [Glycine max]

Eremothecium ashbyi and E. coryli were present in the maxillary and mandibular stylet pouches of the contaminated heads of the true bug Riptortus pedestris collected during a field survey, 2007. Ascospores of E. ashbyi and E. coryli were taken up in the stylet pouch when R. pedestris fed on soybean seeds infected with the respective fungus. In the case of E. ashbyi , the ascospores had subsequently germinated and were recognized as large masses of mycelia in the stylet pouch. In contrast, masses of E. coryli including buds of irregular size and shape were recognized about 3 days after. These results proved that these yeasts are taken up and become lodged in the stylet pouch when the insect feeds on infected host plants. In stylet sheaths stained with erythrosine, E. ashbyi was found as fragments of mycelia and E. coryli was found as small buds. These observations yield evidence to confirm that E. ashbyi and E. coryli are transmitted as fragments of mycelia and as small buds, respectively, after the insect has fed on infected host plants.