DisplayTitle

First Report of Cucumber mosaic virus in Helleborus foetidus in France and Italy

Helleborus foetidus L. (bear's foot) is a perennial plant from the family Ranunculaceae that is common in chalky soils of southern and western Europe. It is grown in gardens for its palm-shaped leaves and early flowers. In 1995, yellow-to-white oak leaf and line patterns in leaves of H. foetidus plants were observed in Hunawihr (Alsace, France). The same symptoms were observed in plants in Entrevaux, Biot, and Gourdon (Provence-Alpes-Côte d'Azur, France) in 2000 and 2001, in Triora (Liguria, Italy) in 2002, and on cv. Western Flisk in a nursery in Nice (Provence-Alpes-Côte d'Azur, France) in 2002. Samples collected from these six locations contained six isolates that were further characterized. Sap extracted from symptomatic plants was mechanically inoculated onto Nicotiana tabacum cvs. Xanthi-nc and Samsun, Chenopodium quinoa, C. amaranticolor, Vigna unguiculata cv. Black, and Cucumis sativus cv. Poinsett. Symptoms exhibited by the inoculated plants indicated infection by Cucumber mosaic virus (CMV). Sap extracted from symptomatic plants reacted positively in double-antibody sandwich-enzyme-linked immunosorbent assays (DAS-ELISA) to antibodies raised against CMV (2). Isometric particles (approximately 30 nm) were observed with an electron microscope in crude sap preparations from infected plants. Following purification of the suspect virus from infected N. tabacum (2) and treatment with formaldehyde (1), each isolate was shown to belong to group II of CMV strains (1,3) by double-immunodiffusion analysis. Following isolation from local lesions on V. unguiculata, the Hunawihr isolate was grown in cv. Xanthi-nc plants and back-inoculated to 2-year-old uninfected seedlings of H. foetidus by aphids (Myzus persicae) or mechanical transmission. Mechanical transmissions were also performed with sap extracted from cv. Xanthi-nc plants infected with the D strain, which belongs to group I of CMV strains (3). Three months postinoculation, symptoms previously described in the original plants were observed in 3 of 10 mechanically inoculated plants and in 2 of 14 aphid-inoculated plants (Hunawihr isolate), whereas no symptoms could be seen in any of the six plants inoculated with the D strain. On the basis of DAS-ELISA, 7 of 10 plants mechanically inoculated and 7 of 14 plants aphid inoculated with the Hunawihr isolate were infected with CMV, whereas 3 of the 6 plants inoculated with the D strain were infected with CMV. To our knowledge, this is the first report that H. foetidus is a natural host for CMV. Beyond the direct impact of the disease induced by CMV on H. foetidus, this perennial and widespread plant species can be an important reservoir of CMV.

References: (1) J. C. Devergne and L. Cardin. Ann. Phytopathol. 7:225, 1975. (2) J. C. Devergne et al. Ann. Phytopathol. 10:233, 1978. (3) M. J. Roossinck. J. Virol. 76:3382, 2002.