Characterization of Seuratia millardetii on Camellia species and in artificial culture
A sooty mold-like disease of Camellia species is observed frequently in the Pacific Northwest but the identity of the causal organism has not been reported. To clarify taxonomy of the fungus associated with the disorder, affected Camellia leaves were collected from locations in Seattle, WA, and from the Camellia collection of the Washington Park Arboretum, University of Washington. The fungus on affected leaves was determined to be Seuratia millardetii (anamorph: Atichia glomerulosa ), a member of the Myriangiales sensu Barr known previously from conifer species in the region. Fungal colonies ranged from less than 0.1 mm to 5 mm in diameter, and were cushion-shaped to lobed. Colonies consisted of a peridium of melanized cells containing enclosing globose, hyaline cells in a gelatinous matrix; hyphae were lacking. Dimorphic macroconidia and microconidia (determined in this study to be phialospores) typical of A. glomerulosa were observed. The teleomorph included bitunicate asci and ascospores typical of S. millardetii. Observation with SEM confirmed that colonies grew superficially on leaves without penetrating them. Colonies in culture resembled those on host leaves, produced dimorphic macroconidia, but grew indeterminately to become several cm across. The fungus was observed on several named cultivars of C. japonica, C. sasanqua, and C. x williamsii. Although known previously from a wide variety of angiosperm and conifer hosts, this is the first time S. millardetii has been reported on Camellia spp. This is also the first report of the teleomorph of this fungus in the Pacific Northwest, and the first description of the fungus in artificial culture.
exobiology; microcolonial fungi; Myriangiales; phylloplane; plant pathogen
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