Taxonomy and Ecology Of Inland Sand Dune ... - Mycorrhizae

6Recently Tommerup andSivasithamparam (1990) describedzygospore formation in Gigaspora.Zygosporangia, zygospores or asexualsporangiospores are not reported in theother five genera, viz., Glomus,Sclerocystis,Acaulospora,Entrophospora, and Scutellospora.Therefore these five genera cannot beplaced in the Zygomycetes withcertainty (Walker, 1987).A. REPRODUCTIVESTRUCTURES1. SPORE FORMATIONThe genera of VAM fungi are separatedon the basis of asexual (anamorphic)spore formation and sporecharacteristics. The terms azygospore orchlamydospore describe the anamorphicstage of VAM fungi. Walker andSanders (1986) did not believe that therewas good evidence for a sexual processin the formation of these spores, nor didthey have evidence that these sporeswere exclusively asexual. Therefore,they suggest using the simple term"spore" to avoid the use of azygosporewith its implied "sexual" connotation.They agreed with Koske et al. (1983),who questioned the use of the termazygospore for the description ofGigaspora reticulata, and with Koskeand Walker (1984 and 1985) whodropped the term without comment.This approach of avoiding a prefixminimizes misrepresentation of thespore type. Unfortunately, this approachdoes not draw attention to the significantdifferences that exist betweenreproductive structures produced bydifferent taxa of VAM fungi.Researchers were encouraged to create asuitable alternative approach to thereproductive structures in VAM fungi(Morton, 1988).Spores in Zygomycetes can be producedsexually or asexually. Zygospores areproduced sexually by the union ofgametangia - morphologicallydifferentiated or undifferentiated somatichyphal cells. Asexual spores areproduced endogenously assporangiospores or modified somaticcells, e.g., chlamydospores (Benjamin,1979).