Conidial Morphology, Pathogenicity and Culture Characteristics of Phomopsis Isolates from Peach, Japanese Pear and Apple in Japan

Abstract

To classify Phomopsis isolates from fruit trees, we examined their conidial morphology, pathogenicity and culture characteristics. Two types of colony, designated W and G, were recognized among Phomopsis isolates from peach, Japanese pear and apple. These types of isolates were not correlated with their original hosts. The lengths of alpha conidia were similar in both W and G type isolates. Both alpha and beta conidia were produced by all isolates of W-type, whereas only alpha conidia were observed in isolates of G-type when cultured on potato dextrose agar at 25°C. In cross-inoculation tests using cut twigs, isolates of both types were pathogenic on other hosts as well as on the original host. In the field inoculation tests, G-type isolates were generally more virulent in twigs or branches of peach, Japanese pear and apple than were W-type isolates. These results suggest that the Phomopsis isolates from peach, Japanese pear and apple are grouped into two specific or infraspecific taxa.