Brown leaf spot disease of gentian, Gentiana scabra var. buergeri (Miq.) Maxim. and its causal fungus
2009
Kobayashi, T.(Tokyo Univ. of Agriculture (Japan)) | Kasuyama, H. | Nasu, H. | Ono, Y. | Watanabe, K.
A new disease, brown leaf spot of gentian, Gentiana scabra var. buergeri (Miq.) Maxim. was first found in 1984 in Okayama Prefecture, and then in Iwate Prefecture, Japan. The spots are first pale brown, then turn to grayish white, often with a purplish brown border. Diseased leaves usually dry out without early defoliation. Often flower buds are infested. Fruiting bodies of a fungus develop on the leaf spots and have a unique morphological development. Spraying a suspension of conidia-like propagules from the fruiting bodies or placing a disc of the isolated fungal colony on the leaves resulted within 1 to 2 weeks in the appearance of the leaf spot symptoms the same as in field. The pathogen was similar to hyphomycetous genus Mycochaetophora Hara et Ogawa established in 1931 for the fungus that causes circular leaf spot of Zelkowa serrata (Thunb.) Makino. But Zelkowa serrata did not develop any disease after inoculation with the fungus isolated from gentian. Because the sizes of the sporophore and conidium of the gentian fungus also differs from the Mycochaetophora pathogen of Zelkowa, the present fungus was treated as a new species of the genus Mycochaetophora, and named M. gentianae Tak. Kobay., Kasuyama et Nasu.
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