In vitro spore formation and completion of the asexual life cycle of Neozygites parvispora, an obligate biotrophic pathogen of thrips

Capilliconidia, the asexual secondary spores of Neozygites parvispora (Zygo mycetes, Entomophthorales) were produced in vitro either by entrapment of v egetative cells (hyphal bodies) in alginate pellets or after plating them o nto water agar. Cultivation of the fungus for 3 days in a medium lacking he molymph increased spore production 30 to 40-fold, and about 10% of the cell s produced capilliconidia. The in vitro produced capilliconidia were infect ious to Thrips tabaci and the fungus was reisolated from infected insects, thus completing its asexual life cycle under laboratory conditions. A decre ase in capilliconidia production and a modification of the number of nuclei per spore were observed for isolates cultivated in vitro for more than 2 m onths, but subsequent host passages restored and increased sporulation effi ciency without influencing the number of nuclei. Fungal cultures were store d at -80 degreesC for up to 7 months, and the capability to sporulate and i nfect T. tabaci was preserved. A bioassay procedure for infecting T. tabaci with N. parvispora is described, the first mycosed insects dying usually a fter 8 d of incubation.