USE OF THE OPTICAL BRIGHTENER TINOPAL BOPT FOR THE RAPID-DETERMINATION OF CONIDIAL VIABILITIES IN ENTOMOGENOUS DEUTEROMYCETES

Viable conidia of Beauveria bassiana and Metarhizium anisopliae fluoresced only weakly after staining in bi-striazinyl amino stilbene (0·05% Tinopal BOPT) and exposure to uv light. By contrast, non-viable conidia fluoresced brightly and could be distinguished from viable spores. A comparison between the fluorescent method and a conventional technique, measuring conidial germination on agar gave good correlations between the two methods for all five B. bassiana isolates examined. With M. anisopliae the two methods gave similar results for var. anisopliae strains but not for var. majus isolates. The fluorescent method was used to determine viabilities of lyophilized B. bassiana conidia stored at 5 and 20 °C. Good correlation between the two methods was obtained up to 451 d at the lower temperature but only for 95 d at 20°. The implications of the results are discussed. © 1990, British Mycological Society. All rights reserved.