A rapid method for assessing the viability of fungal spores

The LIVE/DEAD((R)) BacLight(TM) Bacterial Viability Kit (L-7007) manufactured by Molecular Probes, Inc. (Eugene, Oregon, U.S.A.), which provides a two-colour fluorescence assay of bacterial viability, was useful for determining the viability of the hyaline spores of Colletotrichum gloeosporioides f. sp. malvae, Leptosphaeria maculans, and Sclerotinia sclerotiorum and the thick-walled spores of Alternaria brassicae. Under blue light, viable spores fluoresced green and dead spores fluoresced red. Cells of multicellular spores fluoresced green or red according to their viability. In tests performed with S. sclerotiorum, there was no significant difference between viability as determined with the kit and in vitro germinability. With C. gloeosporioides, the proportion of spores that germinated in vitro was lower than the proportion of viable spores, indicating that not all viable spores could germinate.