Multiple Colletotrichum species cause anthracnose disease on Japanese pickling melon var. Katsura-uri (Cucumis melo var. conomon)

Abstract

Katsura-uri is a variety of Japanese pickling melon (Cucumis melo var. conomon) and traditionally cultivated in the Kyoto area in Japan. The thick flesh and crunchy texture of the fruit are excellent for making Japanese pickles. In 2010, dark brown to black anthracnose spots were found on ripening Katsura-uri fruits after harvest. Four fungal strains (T1, K1, K2 and K3) were isolated from lesions on fruits and identified as four Colletotrichum species (C. orbiculare, C. fructicola, C. aenigma and C. chlorophyti) based on phylogenetic analysis. C. orbiculare K3 isolate caused necrotic lesions on Katsura-uri leaves, whereas C. fructicola K1, C. aenigma K2 and C. chlorophyti T1 isolates caused necrotic lesions on Katsura-uri fruits but not on leaves. Inoculation assays to ripe and immature Katsura-uri fruits suggested that C. chlorophyti causes a postharvest disease; necrotic lesions developed only on ripe fruits. This study showed that multiple Colletotrichum species caused anthracnose on Katsura-uri fruits.