First Report of Zonate Leaf Spot of Cinnamomum kanehirae Caused by Hinomyces moricola in Taiwan.

Abstract

Cinnamomum kanehirae, a native tree of Taiwan, is an important tree that hosts popular medicinal fungi. In the winter of 2011, zonate leaf spots were observed at a nursery garden in Wu-Lai, Taiwan. Initial symptoms included small brown lesions on leaves that became larger leaf spots after expanding or fusing together, causing a leaf blight and eventually defoliation. Sporophores on the host were generally hypophyllous but sometimes amphigenous, solitary, erect, easily detachable. The upper portion of the sporophore was considered an individual conidium and consisted of a pyramidal head that was fusiform to ventricose, 320 to 580 μm long and 100 to 130 μm wide at the broadest point. Branches within the pyramidal head were short and compact, and dichotomously or trichotomously branched. The sporophore initials were hyaline, broad, septate, tapering toward an acute apex, and sometimes constricted at the basal septum. Sclerotia were observed in older lesions, grey or black, spherical, and 1 to 2.5 mm in diameter. The fungus was isolated from infected tissue and sporophores, maintained on potato dextrose agar (PDA) at 20°C in darkness. Sclerotia were produced on PDA after 4 to 5 weeks and were irregular or spherical, but sporophores didn't develop on agar medium. The fungus was identified as Hinomyces moricola on the basis of morphological characteristics (1). Koch's postulates were performed by inoculating four 1-year-old, asymptomatic, potted C. kanehirae plants; every plant was inoculated with sporophores from infected leaves on each of five leaves. Four noninoculated plants were kept in separate pots and served as controls. All plants were covered with transparent plastic bags individually and incubated in a growth chamber at 18 to 20°C. Symptoms were observed after 2 to 4 days on every inoculated plant but not on uninoculated plants. The leaf spots were similar to those originally observed. The pathogen was reisolated from spots of inoculated plants. The pathogenicity test was repeated once. H. moricola is known to cause severe defoliation on woody and annual plants, including at least 73 host species and 36 families distributed in the eastern United States and Japan (2).