Widespread Occurrence and Low Genetic Diversity of Colombian datura virus in Brugmansia Suggest an Anthropogenic Role in Virus Selection and Spread

Chellemi, D. O., Webster, C. G., Baker, C. A., Annamalai, M., Achor, D., and Adkins, S. 2011. Widespread occurrence and low genetic diversity of Colombian datura virus in Brugmansia suggest an anthropogenic role in virus selection and spread. Plant Dis. 95:755-761. Brugmansia (Brugmansia spp.) is a perennial shrub in the Solanaceae, originating from South America, that is a popular landscape plant in the tropics and subtropics and container plant in temperate regions. Virus-like symptoms including mosaic, rugosity, and faint chlorotic spots were first observed on leaves of Brugmansia plants in a south Florida nursery in November 2003. Colombian datura virus (CDV) was identified in these initial plants and subsequent Brugmansia and Datura metel (a Brugmansia relative also grown as an ornamental) plants obtained from Florida, Connecticut, Wisconsin, and California. Overall, 77.5% of Brugmansia and two of four D. metel plants tested were infected with CDV. Partial NIb/CP sequences of 28 Brugmansia CDV isolates from this study were compared with all 16 CDV isolates in GenBank and found to share high levels of nucleotide and amino acid identity, with negative selection estimated to be occurring. A single Brugmansia plant was also infected with a recently described tobamovirus. The low genetic diversity of CDV observed, along with negative selection pressure on NIb/CP, suggests a recent ancestry (<400 years) of the worldwide population of CDV, coinciding with anthropogenic collection and dissemination of Brugmansia plants from their center of origin. Brugmansia (Brugmansia spp.), also known as Angel’s trumpet, is a solanaceous ornamental that produces large, fragrant, and attractive flowers. Seven wild Brugmansia species can be differentiated (3,32), all native to either the lowland tropical or Andes mountain regions of South America. Additionally, several multiplespecies hybrids exist in the wild without intentional anthropogenic pollination, including B. × candida (B. aurea × B. versicolor) (28). In its native habitat, Brugmansia are semi-woody perennial trees or shrubs distinguishable from members of the closely related genus Datura by growth pattern, and fruit and seed morphology. All Brugmansia species contain high concentrations of alkaloids including atropine, hyoscyamine, and hyoscine (7), and it is for this reason that it has been cultivated, traded, and used for centuries by native South Americans for ceremonial and cultural purposes (7,29). In the more temperate climates of North America, Europe, and Asia, Brugmansia species have become widely popular (following their introduction during colonial times) among botanists, gardeners, and plant collectors as large container specimens due to the vast array of flower shapes, colors, and scents (Fig. 1). Brugmansia is highly valued by amateur and commercial plant breeders because of the ease of hybridization between different species, and the simplicity with which it can be vegetatively propagated and disseminated as cuttings. Well over 200 Brugmansia cultivars, including many multiple-species hybrids, have been registered by several organizations (e.g., 1; http://www.brugmansia.us/), and plants are commonly traded or sold among Brugmansia enthusiasts around the world.