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First Report of Neofusicoccum parvum Causing Dieback Disease of Chinese Weeping Cypress in China

Cupressus funebris Endl. (Chinese weeping cypress) is native to southwestern and central China. In June 2008, blighted shoots of Chinese weeping cypress trees were observed in Yunnan Province (southwestern China). Symptomatic trees were located in an ornamental planting established approximately 8 to 12 years ago. Additional samples were collected from 11 locations in the provinces of Sichuan, Yunnan, Guizhou, and Chongqing. Disease symptoms included yellowing and wilting of leaves on several branches, followed by sudden death within 6 to 8 weeks. Cross sections on trunks and branches revealed darkened zones. Tissue from diseased samples was plated on potato dextrose agar (PDA) and incubated at 25°C. Fungal isolates developed copious, white, aerial mycelium that became dark gray after 4 to 6 days and formed black pycnidia after 25 days. Conidia were hyaline, ellipsoidal to fusiform, externally smooth, thin walled, nonseptate, and measured 12.5 to 18.5 × 4.0 to 6.5 μm. Identity was confirmed by analysis of the rDNA internal transcribed spacer region (ITSI-5.8S-ITS2) and the translation elongation factor 1-alpha (EF1-α). BLAST searches at GenBank showed a high identity with reference sequences (ITS: >99%; EF1-α: 100%). Representative sequences of both regions were deposited in GenBank (ITS: Accession No. FJ842960 and FJ842961; EF1-α: Accession No. GU811148). Morphological and molecular results confirmed this species as Neofusicoccum parvum, reported as the anamorph of Botryosphaeria parva. Pathogenicity tests were conducted by stem inoculation of 2-year-old C. funebris seedlings. Mycelial plugs (4 mm in diameter) of N. parvum from actively growing colonies were applied to same-size bark wounds on the middle point of the stems. Control seedlings were inoculated with sterile PDA plugs. Inoculated and control seedlings (five each) were kept in a greenhouse and watered as needed. After 5 weeks, all C. funebris seedlings showed leaf wilting and dark vascular stem tissue. N. parvum was reisolated from all inoculated, symptomatic tissues, fulfilling Koch's postulates; no symptoms were visible in the control seedlings. N. parvum has previously been reported to cause canker and dieback disease of avocado (3), mango (2), and magenta cherry (Syzygium paniculatum) (1). To our knowledge, this is the first report of N. parvum causing dieback of C. funebris in China.

References: (1) R. C. Ploetz et al. Plant Pathol. 58:801, 2009. (2) B. Slippers et al. Mycologia 97:99, 2005. (3) T. Zea-Bonilla et al. Plant Dis. 91:1052, 2007.