Molecular markers are described for determining the presence or absence of a gene conferring resistance to tomato yellow leaf curl virus from S. chilense (Ty-1) in a host plant. Also described, are methods for producing a host plant comprising a gene conferring resistance to tomato yellow leaf curl virus from S. chilense (Ty-1), including the analysis of the presence or absence of the molecular markers. A plant, and parts thereof, obtained by such a method are also described.
