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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Emerging Pests and Pathogens Research » Research » Publications at this Location » Publication #306227

Title: Confirmation of Neozygites floridana azygospore formation in two-spotted spider mite (Tetranychus urticae) in strains from tropical and temperature regions

item WESTRUM, KARIN - Norwegian Institute For Food Research
item DUARTE, VANESSA - Universidad De Sao Paulo
item Humber, Richard
item DELALIBERA, ITALO - Universidad De Sao Paulo
item KLINGEN, INGEBORG - Norwegian Institute For Food Research

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2014
Publication Date: 10/1/2014
Citation: Westrum, K., Duarte, V.S., Humber, R.A., Delalibera, I.J., Klingen, I. 2014. Confirmation of Neozygites floridana azygospore formation in two-spotted spider mite (Tetranychus urticae) in strains from tropical and temperature regions. Journal of Invertebrate Pathology. 122:1-5.

Interpretive Summary: The mechanical details of how the thick-walled resting spores of fungi in the phylum Entomophthoromycota form and whether these resting spores represent the sexual stage in the life history of these fungi has remained controversial. This study examines the development of resting spores by Brazilian and Norwegian strains of a single fungus, Neozygites floridana, that is a major pathogen of agriculturally important mites. N. floridana resting spores may develop after (presumably sexual) conjugations of two cells or from single cells with no prior cellular conjugation (yielding resting spores of a ‘nonsexual’ origin). The number of nuclei in resting spores of both types were monitored, and showed nearly identical behaviors so that regardless of the number of nuclei in young spores, the mature spores tended to contain only two nuclei; it is assumed (but remains unproved) that these two nuclei may undergo fusion and then reduction division (meiosis) during the germination of the thick-walled resting spores. These behaviors are important because they help to underscore that the definition of sexuality for entomophthoromycotan fungi must be based on independent criteria based on either morphological events (whether cellular conjugations do or do not precede formation of the resting spore) or genetic events (whether two nuclei fuse and then undergo reduction divisions or meiosis). The Entomophthoromycota is exceptional because in virtually all other fungi, plants, and animals the morphological and genetic events of sexual reproduction are obligatorily linked.

Technical Abstract: Neozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygospores remained to be fully confirmed. In this study, we document the formation of azygospores by a Brazilian N. floridana strains and the formation of azygospores and zygospores by a Norwegian N. floridana strain both found in the same individual in the Norwegian strains. Further we report the presence of immature azygospores with 1-3 nuclei for the Norwegian strains, immature resting spores (probably azygospores) with 1-8 nuclei for the Brazilian strain, and mature resting spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygospores). Our observations suggest that th eimmature resting spores (prespore) of both strains begins in a multinucleate condition but that tht enuclear number is reduced during maturation until the mature resting spore is binucleate regardless of its origin as a zygospore or azygospore.