Production of a Fungistat and the Role of Fungi during Germination of Digitalis purpurea L.cv. Gloxiniaflora Seeds

The seed coats of Digitalis purpurea L. cv. Gloxiniaflora werecultured for indigenous fungi. Alternaria alternata (Fries)was identified as the sole fungus on seeds freshly harvestedfrom unopened capsules, whereas A. alternata, Rhizopus arrhizus(Fischer), Penicillium sp. and other fungi appeared on storedseeds. The appearance of fungi in seed cultures was seasonal,being more frequent in winter and early spring than in summerand autumn. Alternaria grew well on autoclaved seeds, on dehiscentseed coats, or on seed coats separated from the embryos of ungerminatedseeds. Rhizopus did not grow on these but grew weakly on theculture medium from viable seeds. A. alternata appears to functionas a degradation agent for the seed coat subsequent to germination.Neither fungus was found to be essential to germination of Digitalisseeds. Bioassay of the culture medium from germinating seedsshowed that a fungistat effective against both Alternaria andRhizopus is produced coincident with germination. Based on chromatographicanalysis, the fungistat appears to be a cardenolide. Alternaria alternata (Fries), cardenolides, Digitalis purpurea L. cv, Gloxiniaflora, fungistats, germination, Rhizopus arrhizus (Fischer)