Abstract
An apothecium was found on apple leaves infected with blotch which had been overwintered out of doors on the ground. The ascospore grown on a culture medium produced Marssonina-type conidia. The ascospore caused typical symptoms of blotch when inoculated to apple leaves. The apothecium produced on overwintered diseased leaves is the perfect state of the causal fungus of blotch, Marssonina coronaria (Marssonina mali). After Nannfeldt's classification, the perfect state of the fungus belongs to the genus Diplocarpon of Dermateaceae, Helotiales. Morphological characters and host plants of the present fungus are distinct from those of the species known hitherto in this genus, hence Diplocarpon mali Y. Harada et K. Sawamura, sp. nov., is proposed for it. A possible role of the ascospores as primary inocula in spring to early summer is suggested.
