科研之友
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摘要
Black spot is a common disease occurring on Dendrobium officinale, which significantly reduces the quality and yield of this medicinal plant (family Orchidaceae). The disease manifests itself as small, black spots on leaves which can develop into circular streaks that become necrotic tan or brownish black, with the leaves eventually turning yellow or brown-yellow. Fungal pathogens such as Alternaria tenuissima and Phyllosticta spp. are known to cause black spot of D. officinale. A fungus which was atypical of A. tenuissima or Phyllosticta spp. was isolated from leaves of D. officinale showing symptoms of black spot from Zhejiang and Guangxi provinces, China. Pathogenicity tests in vitro as well as on tissue-cultured seedlings using fungal isolate GXDF24 showed that it was able to cause typical black spot symptoms. Molecular identification based on the ITS sequence revealed that isolate GXDF24 shared 99% similarity with Cladosporium oxysporum. This is the first report of C. oxysporum as a pathogen causing black spot of D. officinale in China.
