Mercurialis ambigua and Solanum luteum: two newly discovered natural hostsof tomato yellow leaf curl geminiviruses

The yellow leaf curl disease of tomato is caused by a complex of virus spec ies, two of which, tomato yellow leaf curl virus (TYLCV)-Sar and TYLCV-Is, are involved in epidemics of southern Spain. Plants of Mercurialis ambigua and Solanum luteum showing abnormal upward leaf curling and leaf distortion collected in the vicinity of tomato crops were found to be naturally infec ted with TYLCV-Is and TYLCV-Sar, respectively. These weed species, as well as Datura stramonium and S. nigrum, which had also been found to be natural ly infected by TYLCVs in the same region in previous studies, were tested f or susceptibility to TYLCV-Sar or TYLCV-Is by Agrobacterium tumefaciens-med iated and by Bemisia tabaci inoculation. Results indicated that both TYLCV- Sar and TYLCV-Is were able to infect D. stramonium and M. ambigua, whereas only TYLCV-Sar infected S. nigrum and S. luteum. Implications for the epide miology of TYLCV are discussed. This is the first report of M.ambigua and S . luteum as hosts of TYLCV.