Natural Infection of Field-Grown Borage (Borago officinalis) by Alfalfa mosaic virus in Spain.

Alfalfa mosaic virus (AMV) has a wide host range and is distributed throughout the world. It causes disease in several vegetable crops, including bean, celery, lettuce, pea, pepper, and tomato (1). In Spain, it has been found naturally infecting alfalfa, pepper, and tomato. During the autumn of 1999, in the area of Zaragoza (northeastern Spain), several plants expressing foliar yellow mosaic symptoms were observed in borage grown for human consumption in open field plots. The commercial value of the symptomatic plants was greatly reduced. The symptoms were similar to those previously obtained in greenhouse-grown borage plants mechanically inoculated with three tomato isolates of AMV (2). The following indicator species, including virus-free borage plants, were mechanically inoculated with sap from leaves of symptomatic borage plants, and reactions were recorded: chlorotic and necrotic local lesions on Tetragonia expansa and Vigna unguiculata; chlorotic local lesions and systemic mosaic on Chenopodium quinoa, C. amaranticolor, Cucumis sativus 'Marketmore', Gomphrena globosa, and Nicotiana glutinosa; systemic mosaic, sometimes associated with localized reactions, on Ocimum basilicum, Capsicum annuum 'Doux des Landes' and 'Yolo Wonder', N. benthamiana, N. clevelandii, N. rustica, N. sylvestris, N. tabacum 'Paraguay' and 'Xanthi nc', Petunia hybrida, Physalis floridana, and Solanum melongena 'Cerna krazavitska'. The reactions are in agreement with the indicator host reactions described for AMV (1). Symptoms on virus-free borage plants mechanically inoculated with sap from symptomatic borage and from inoculated C. amaranticolor and O. basilicum experimental hosts were similar to those observed in naturally infected borage. Positive serological reactions (A₄₀₅ values more than three times greater than those of the negative controls) in double-antibody sandwich enzyme-linked immunosorbent assay using commercially prepared antiserum against AMV (Agdia, Inc., Elkhart, IN) were obtained with extracts of naturally infected borage leaves and with systemically infected indicator species. Alfalfa plots located in the vicinity of the symptomatic borage plants could be the source of virus for borage infections. To our knowledge, this is the first report of natural AMV infection in Borago spp. References: (1) E. M. J. Jaspars and L. Bos. CMI/AAB. No. 229, 1980. (2) M. Luis-Arteaga and J. M. Alvarez. Inf. Téc. Econ. Agr. 92:70, 1996.