Three species of Exobasidium causing Exobasidium leaf blight on subgenus Hymenanthes, Rhododendron spp., in Japan

Abstract

Three Exobasidium species causing Exobasidium leaf blight on Rhododendron of subgenus Hymenanthes in Japan are described and discussed. After examining the holotype and fresh materials of E. shiraianum on R. degronianum, its description is emended by the morphology of basidiospores that are ellipsoid to ovoid, or obovoid, 11-21 ϫ 5-8 µm, and with 1-3 septa. Culture of this species showed yeast-like growth. Exobasidium woronichinii on R. brachycarpum observed from Hokkaido Prefecture to Nagano Prefecture is described as a new species characterized by its ellipsoid to ovoid, 11-19 ϫ 3-4.5 µm, and 1-5(-6)-septated basidiospores. Culture of this species was gelatinous but obtrite, or thick and showed farinose appearance by conidiation. A fungus on R. aureum in Hokkaido and Nagano Prefectures is identified as E. caucasicum. This species is new to Japan and is characterized by its ellipsoid to ovoid, or obovoid, 11-19 ϫ 3-6 µm, and 0-2-septated basidiospores. Culture of this species showed yeast-like growth.

Leaf blister on two Ericaceae plants infected by Exobasidium species in Japan

“…Exobasidium Woronin, 1867 comprises 129 epithets listed in the Index Fungorum (http://www.indexfungorum.org/names/names.asp, accessed on October 21, 2021) and is the largest genus under Exobasidiales. Most species of the genus are known as plant pathogens that cause plant deformities characterized by blisters, witches' brooms, and galls on leaves, stems, flowers, shoots, and buds (Brewer et al, 2014; Ezuka, 1990a, 1990b, 1991a, 1991b; Nagao et al, 2001, 2006; Nagao, Kakishima, Akimoto, et al, 2003; Nagao, Kakishima, Kurogi, & Sato, 2004; Nagao, Kakishima, Ogawa, & Sato, 2003; Nagao, Kakishima, & Sato, 2004). These fungi infect several plants belonging to the family Ericaceae, such as Theaceae and Symplocaceae.…”

Common problems of <i>Rhododendron</i> L. in the Central Botanical Garden of the National Academy of Sciences of Belarus

“…В процессе интродукции растений из других районов и областей земного шара они вступают во взаимодействие с местными патогенами и фитофагами, а кроме того, существует реальная опасность заноса присущих им возбудителей болезней и вредителей, которые ранее не встречались в республике [1,9]. Анализ литературных данных показал, что на рододендронах известно более 40 видов возбудителей болезней и вредителей [2,[10][11][12][13][14][15][16][17][18][19][20][21][22][23]. К За все время существования коллекции рододендрона целенаправленного исследования ее фитосанитарного состояния не проводилось, а накопленные сведения о вредителях и болезнях были незначительны [1,7,24].…”