Fl. Walley et Jj. Germida, ESTIMATING THE VIABILITY OF VESICULAR-ARBUSCULAR MYCORRHIZAE FUNGAL SPORES USING TETRAZOLIUM SALTS AS VITAL STAINS, Mycologia, 87(2), 1995, pp. 273-279
The tetrazolium salts -dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoli
um bromide and ophenyl)-3-(p-nitrophenyl)-5-phenyl-2H-tetrazolium chlo
ride were evaluated as viral stains for estimating the viability of fu
ngal spores of Glomus mosseae and Glomus clarum. Respiring fungal spor
es accumulated tetrazolium bromide-formazan and tetrazolium chloride-f
ormazan in the cytoplasm as a visually distinct color reaction. Estima
tes, however, of fungal spore viability based on tetrazolium bromide s
taining were inconsistent with viability estimates based on a bioassay
using single spores of G. clarum. Inconsistencies were due largely to
the ambiguous interpretation of the significance of black spores. In
contrast, color reactions in tetrazolium chloride were relatively stab
le and consistent with bioassay estimates of viability. Generally, inc
ubation in 1 mg ml(-1) tetrazolium chloride for 48 to 72 h was suffici
ent to ensure maximum color reaction. Viable spores were distinguishab
le from those which were unable to colonize a host plant on the basis
of the intensity of color reaction in tetrazolium chloride. We conclud
e that tetrazolium chloride staining can be used as a rapid indicator
of vesicular-arbuscular mycorrhizae fungal spore viability.