Occurrence of Chilli veinal mottle virus in Solanum aethiopicum in Tanzania.

Abstract

African eggplant, or garden egg (Solanum aethiopicum) is an important vegetable in most sub-Saharan African countries. Since June 1997, viral symptoms, including mosaic, vein clearing, and stunting, have been observed on several crops of African eggplant cv. Tengeru White at a number of sites in the Arusha region of northern Tanzania. Field inspections revealed disease incidence ranging from 50 to 90%. During the same period, high populations of the green peach aphid Myzus persicae were observed in affected crops of African eggplant. These aphids were also found to reproduce in African eggplants. Flexuous, rodshaped virus-like particles, approximately 750 nm long and 12 nm wide, were found in electron microscope leaf dips from field samples of naturally affected African eggplants. The particle size suggested a species of Potyviridae. Thus, 20 field-infected samples of S. aethiopicum (randomly collected from four farms) were assayed in double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for the presence of Potato virus Y (PVY) and Pepper veinal mottle virus (PVMV), known to infect tomato and other solanaceous crops in the region (2). However, all samples gave negative results. Further DAS-ELISA were performed with the same extracts from naturally infected plants of S. aethiopicum with antisera directed against Tobacco etch virus, Tobacco vein mottling virus, Pepper mottle virus, and Chilli veinal mottle virus (ChiVMV). All 20 samples were positive only for ChiVMV. ChiVMV, a single-stranded RNA virus transmitted in a nonpersistent manner by several aphid species, is one of the most important viruses of pepper in Asia (1). To confirm DAS-ELISA results, an isolate of ChiVMV from African eggplant was transmitted by mechanical inoculations, resulting in disease on tobacco (Nicotiana tobacco cv. Xanthi nc), pepper (Capsicum annuum cv. Yolo Wonder), tomato (Lycopersicon esculentum cv. Tengeru 97), and African eggplant (S. aethiopicum cv. Tengeru White). Extracts from the inoculated plants tested positive for the presence of ChiVMV in DAS-ELISA. This mechanically transmitted isolate did not infect melon (Cucumis melo), cucumber (C. sativus), or cowpea (Vigna unguiculata), which are nonhosts of ChiVMV. To our knowledge, this is the first report of the natural occurrence of ChiVMV in African eggplant.