Spore morphology of Nosema furnacalis and infectivity for a clone of the Helicoverpa zea cell line were examined by both light and electron microscopy. Dimorphic spores were found in cultured cells infected with N. furnacalis. One type having a few coils of the polar filament (FC spore) germinated spontaneously inside or outside the cell after formation. The other type had many coils of the polar filament (MC spore). The FC spores possessed four coils of the polar filament and MC spores had nine coils on the average. This spore dimorphism was demonstrated to be a characteristic not limited to N. bombycis . With continued passage, the proportion of FC spores in cultured cells sharply increased. Spores isolated after passage 85 to 90 were used to infect cultured cells without prior priming at an alkaline pH. In cultures inoculated at a rate of 10 spores/cell, the prevalence of infected cells was 45% 24 hr postinoculation and 98% by 96 hr postinoculation.
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- In vitro culture
- Nosema furnacalis
- Spore dimorphism
- Spore germination