PENETRATION AND INFECTION PROCESS OF PHYLLACTINIA-CORYLEA ON MULBERRYLEAF CAUSING POWDERY MILDEW - I - ASEXUAL STAGE

Surface morphology of conidia of Phyllactinia corylea (Pers.) Karst., its germination, penetration of hyphal branches and the infection proc ess on mulberry leaf are described, under scanning electron microscope . Surface of the clavate, hyaline conidium is ornamented with evenly d istributed spine-like protrusions. The conidia germinate 4 h after ino culation, producing a single germ tube mostly from a little behind the distal end of the conidium. The hyphae soon produce special branches, stomatopodia, which enter the leaf through stomata. The stomatopodia are produced singly or in pairs, and one or two stomatopodia enter in a stoma. The branched superficial hyphae forms a mycelial mass within 72 h after inoculation. The disease becomes apparent at conidial stage . The conidiophores were straight at early stages, but appeared spiral ly coiled when the conidia were mature, which may aid for conidial det achment.