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First Report of Anthracnose of Lycium barbarum Caused by Colletotrichum acutatum in China

Barbary wolfberry (Lycium barbarum, Solanaceae) is an important Chinese traditional medicine that is widely planted in northwestern China (6.7 × 10⁴ ha under cultivation, including Ningxia Hui Autonomous Region). After a recent, large increase in the planting area and density, anthracnose has become more damaging. In China, Colletotrichum gloeosporioides was assumed to be the sole causal agent of anthracnose on L. chinense (wolfberry) (3), whereas in Korea, C. dematium was reported to cause anthracnose on wolfberry (4). During the summer and autumn of 2007, 29 barbary wolfberry fruit samples were collected from three orchards in Zhongning County, Ningxia Hui Autonomous Region. Conidia were 8.5 to 16.5 × 2.5 to 4 μm and fusiform or pointed at one or both ends. Slow-growing colonies on potato dextrose agar were white to orange or pink; sclerotia and setae were absent. The morphological traits were identical to those of C. acutatum and clearly distinct from those of C. gloeosporioides (conidia cylindrical with both ends rounded, gray colony color) or C. dematium (conidia falcate, sclerotia and setae abundant) (2--4). Koch's postulates were performed to verify that the isolates were capable of causing anthracnose on wolfberry. Six wolfberry fruits were surface sterilized with 70% alcohol, allowed to dry 1 min, then wounded with a sterile needle, and dipped in 6 ml of spore suspension (1 × 10⁵ conidia/ml). Anthracnose symptoms were observed on inoculated fruit after 3 days, whereas control fruits inoculated with sterile water did not develop symptoms. The pathogenicity test was performed three times; in each trial, fungi reisolated from symptomatic tissue were morphologically identical to those that had been used as inoculum. Amplification of the internal transcribed spacer (ITS) region of rDNA with primers ITS1 and ITS4 resulted in bands of approximately 600 bp. The sequences of both isolates were compared with sequences deposited in the GenBank database and demonstrated 99% similarity to C. acutatum isolate DQ286123. PCR amplification of the ITS region was also carried out using species-specific primer CaInt2 in conjunction with the universal primer ITS4 (1). A DNA fragment of approximately 500 bp was amplified from all isolates, whereas no amplification products were obtained from reference cultures of C. gloeosporioides and C. dematium. To our knowledge, this is the first report of C. acutatum causing anthracnose on L. barbarum.

References: (1) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996. (2) B. C. Sutton. Page 523 in: The Coelomycetes. Commonwealth Mycological Institute, Kew, Surrey, England, 1980. (3) X. M. Wang and J. Y. Li. Acta Mycol. Sinica 6:211, 1987. (4) S. H. Yu. Korean J. Plant Pathol. 2:31, 1986.