1986 Volume 52 Issue 3 Pages 466-474
Grape berries infected by the flyspeck disease, were observed by scanning electron microscopy. The bloom covering the surface of healthy berry consisted of crystalline structure of flake-like appearance. This structure around attaching conidia and growing hyphae of Zygophiala jamaicensis Mason, a causal fungus, has been degenerated probably by enzyme (s) secreted by this fungus and changed into a thin film. Most of hyphae were found to grow underneath such a film. The crystalline structure around apices of growing hyphae remained unaltered but that along the hyphal region 10-15μm and more behind the apex appeared to be altered, suggesting that the bloom-degenerating enzyme (s) might be secreted from the latter region but not apex. The microsclerotium-like structure formed on the bloom-evanescing regions of berry seemed to be formed by a great number of branching hyphae emerged from several, thick hyphae. Micromanipulation at the scanning electron microscope level revealed that the central region of microsclerotium-like structure consisted of 3-4 hyphal layers and the marginal region 2-3 layers. This technique also revealed that there were no fungal structures penetrating cell walls of the berry. These observations support our earlier result by light microscopy that the present causal fungus might be an ectoparasite which lives on the bloom of grape berries.