Mixed infections of grapevine leaf rusts Phakopsora meliosmae-myrianthae and P-montana in Japan

Mixed infections of grapevine leaves by the grapevine leaf rust fungi Phakopsora meliosmae-myrianthae and P. montana were assumed because of the frequent sympatric occurrences of the two species in Honshu, Japan. This assumption was proven by experimental basidiospore inoculations of Meliosma myriantha and M. tenuis. Basidiospores formed on telial clusters from one rusted grapevine leaf infected both M. myriantha and M. tenuis, resulting in spermogonium and aecium production on the inoculated leaves. However, the aeciospores formed on the two Meliosma species differed; those on M. myriantha were apically thick-walled, characteristic of P. meliosmae-myrianthae, and those on M. tenuis were evenly thin-walled, characteristic of P. montana.