VITAL FLUOROCHROMES AS TRACERS FOR FUNGAL GROWTH-STUDIES

Eight fluorescent dyes were tested for staining the spores or mycelia of six fungi and for their translocation into new growth when the prel oaded spores or mycelia were incubated on agar coated coverslips. The dyes studied were Cellufluor, Nile red, fluorescein diacetate (FDA), c arboxyfluorescein diacetate (CFDA), chloromethylfluorescein diacetate (CMFDA), aminochloromethyl coumarin (CMAC), and the carbocyanines DiIC (18)(3) and DiOC(18)(3), The fungi on which the dyes were tested inclu ded Botrytis cinerea, Fusarium oxysporum f.sp. lycopersici, Idriella b olleyi, Pythium oligandrum, Sclerotium cepivorum and Trichoderma harzi anum. Most of the fluorochromes gave good initial staining of mycelia or spores; however, FDA fluorescence faded rapidly during excitation, making it impractical for use, Also, the spores and mycelia of B. cine rea and T. harzianum sometimes gave weak fluorescence with Nile red, a nd the spores and mycelia of I. bolleyi gave unusually weak fluorescen ce with Cellufluor. There were other variations of staining among the different dye/fungus combinations, but each fungus showed strong fluor escence with at least one dye. Cellufluor, CMFDA, CMAC and, to a lesse r extent, CFDA and Nile red, were efficiently translocated into new gr owth from preloaded spores or mycelia, whereas FDA, DiIC(18)(3) and Di OC(18)(3) were not. The extent of translocation ranged from 0.1 to 1.2 mm in germ tubes arising from spores, and from 0.9 to 9.2 mm in mycel ia extending from dye-loaded agar blocks. The findings suggest that fl uorescent dyes could be used as markers or tracers in studies of funga l growth and differentiation.