First Report of Leaf Spot Caused by Phoma multirostrata var. microspora on Dendrobium officinale in Zhejiang Province of China

Abstract

HomePlant DiseaseVol. 102, No. 8First Report of Leaf Spot Caused by Phoma multirostrata var. microspora on Dendrobium officinale in Zhejiang Province of China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Leaf Spot Caused by Phoma multirostrata var. microspora on Dendrobium officinale in Zhejiang Province of ChinaY. Y. Xie, L. P. Wang, L. Fang, and H. R. WangY. Y. Xiehttp://orcid.org/0000-0003-2057-9307Search for more papers by this author, L. P. WangSearch for more papers by this author, L. FangSearch for more papers by this author, and H. R. Wang†Corresponding author: H. R. Wang; E-mail: E-mail Address: wanghrg@126.comSearch for more papers by this authorAffiliationsAuthors and Affiliations Y. Y. Xie L. P. Wang L. Fang H. R. Wang † , Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, P.R. China. Published Online:25 May 2018https://doi.org/10.1094/PDIS-10-17-1629-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Dendrobium officinale Kimura & Migo is an important Chinese medicinal plant belonging to the family Orchidaceae and is widely cultivated in Zhejiang Province of China. It has broad bioactivities including immunomodulation, antifatigue, antioxidation, digestion promotion, antihyperglycemia, and antihypertension (Gao et al. 2002). During the summer months in 2013 and 2014, plants showing necrotic spots (∼5 mm diameter) on the leaves were observed in a field in Deqing county, Zhejiang Province, China. Over 80% of the plants showed symptoms while infected leaves exhibited circular or irregular, \light brown or dark brown spots, often with a central depression and brown margins. There were no symptoms on adaxial sides of leaves. The pathogen was isolated from different affected tissues individually. Four single-spore isolates were obtained and grown on potato dextrose agar (PDA) at 25°C for 7 days. The colonies on PDA were white, rounded, and with radial margins. Pycnidia were globose, 45 to 95 μm, mostly embedded, and appeared as evenly arranged on the surface of the colony after 7 to 10 days. Conidia were single celled, elliptic or oval, 2.8 to 4.8 × 2.1 to 2.7 μm. Morphological characteristics of the isolates were similar to colonies in the genus Phoma (Boerema et al. 2004). PCR amplification of genomic DNA using the primers ITS1 and ITS4 for ITS region (White et al. 1990), ACT-512 F and ACT-783R for ACT (actin gene), and EF1-728 F and EF1-986R for EF-1α (translation elongation factor 1α) (Carbone and Kohn 1999) was performed. Sequence analysis revealed that the isolate HBtp-003 (GenBank accession nos. KU257610 ITS, KX782333 ACT, KX782332 EF-1α) shared 99 to 100% identity with Phoma multirostrata (FJ839841, FJ426920, EU543986, respectively). This isolate was identified as P. multirostrata var. microspora based on the size of the conidia (Boerema et al. 2004). To conduct a pathogenicity test, conidia were obtained from the crushed pycnidia collected from the surface of the colonies. The conidial suspension of P. multirostrata was diluted into 106 conidia/ml using 0.1% CMC-Na solution (CMC, carboxymethyl cellulose). Twenty healthy D. officinale leaves were wound-inoculated on the abaxial side of the leaves with the conidial suspension, and covered by plastic domes for maintaining humidity and temperature. Twenty plants inoculated with 0.1% CMC served as control. All plants were maintained in greenhouse between 25 and 30°C with natural light. Ten days after inoculation, all treated leaves developed spots similar to those in the field. Control plants remained asymptomatic. P. multirostrata was reisolated from all inoculated plants but not from any of the noninoculated plants. Ten wounding leaves were reinoculated with distilled water in our test, and no symptom was observed. To our knowledge, this is the first report of leaf spot disease caused by P. multirostrata var. microspora on D. officinale in China.