Infectious DNA from a whitefly-transmitted virus of Phaseolus vulgaris

Abstract

GOLDEN yellow mosaic (bean golden mosaic) is a widespread disease of Phaseolus vulgaris in tropical and subtropical America¹. The disease causes serious yield losses in several countries where beans are an important dietary staple^2,3. The causal agent, long presumed to be a virus, also infects P. lunatus and Macroptilium lathyroides in the American tropics^4,5. The pathogen is transmitted in nature and in the laboratory by the whitefly Bemisia tabaci Genn., and is also mechanically transmissible from the sap of infected plants^3,5. An unusually small (18-nm diameter) nucleoprotein particle has been purified from diseased plants^5,6, and shown conclusively to be the whitefly-transmitted virus causing the disease⁵. Electron microscopy of purified virus revealed predominately geminate aggregates of the 18-nm particles^5,6. The virus must be aldehyde-fixed before negative staining because it is disruped by the heavy metal salts (ammonium molybdate, sodium phosphotungstate, or uranyl acetate) used as negative stains. Thus, it is not known whether the geminate aggregate is the infectious entity or an artefact of fixation⁵. Nonetheless, its unusually small size sets this virus apart from most other plant viruses. I describe here the extraction of infectious DNA from purified golden yellow mosaic virus (GYMV), a result that further separates this virus from other previously described plant viruses.