Natural infections of Tomato spotted wilt virus (TSWV) found in weeds around tobacco fields in Georgia
Martinez-Ochoa N1, Mullis SW1, Csinos AS1, Webster TM2, Bertrand1 P
1Dept. of Plant Pathology, University of Georgia, Tifton GA 31793 U.S.A.
2CPMRU, USDA-ARS, Tifton GA 31793 U.S.A.
Correspondence: nmartinez8@alltel.net
Tomato spotted wilt virus (TSWV) is now endemic to the southeastern United States, where it affects major agricultural crops such as tomato, pepper, tobacco, peanut and numerous ornamentals as well. Due to milder winters and longer humid and warm summers in Georgia, there are favorable conditions for a succession of plant species that could serve as tospovirus reservoirs and more importantly, for a place for the thrips vectors to reproduce throughout the year. A three-year survey was conducted in nine Georgia tobacco fields to determine the weed species that were naturally infected with TSWV. Samples were taken on a monthly basis from most weed types at each location, and leaf and root tissues were tested together using DAS-ELISA (Agdia Inc.). In the winter and spring, Oenothera laciniata Hill (cutleaf evening primrose), Gnaphalium pensylvanicum Wild. (wandering cudweed), G. purpureum L. (purple cudweed), Eupatorium capillifolium (Lam.) Small (dogfennel), Lepidium virginicum L. (Virginia pepperweed), and Geranium carolinianum L. (Carolina geranium), were among the wild plant species most commonly infected with TSWV. In the summer and fall, the most common species found testing positive for TSWV were Jacquemontia tamnifolia (L.) Griseb. (smallflower morningglory), Richardia scabra L. (Florida pusley), Portulaca pilosa L. (broadleaf pink purslane), Desmodium tortuosum (Sw.) DC. (Florida beggarweed), Amaranthus retroflexus L. (redroot pigweed), and Wahlenbergia marginata (Thunb.) A. DC. (southern rockbell). There were a few plant species that did not test positive for TSWV during the entire survey period, and examples of those were Viola fafinesquii Greene (field pansy), Cardamine hirsuta L. (hairy bittercress), Diodia teres Walt (poorjoe), Veronica arvensis L. (corn speedwell), and Phylotacca americana L. (common pokeweed). Focus in follow-up surveys is being aimed at a select group of the most commonly TSWV-infected weeds found that are also reported as being reproductive hosts for the thrips vectors. In addition to weather and thrips vector populations, it is expected that seasonal incidences of TSWV in their weed reservoirs might be useful in predicting TSWV levels when planting susceptible field crops.
