Development of a Molecular Marker for Geminivirus Resistance Genes in Tomatoes through Analysis of Tomato Resistance Gene Homologues

Each year geminiviruses cause millions of dollars in damage to tomato crops in Central America. Attempts to create a resistant plant with a suitable fruit through breeding programs have been unsuccessful. This study hopes to develop a molecular marker for the gene that controls resistance to geminiviruses. We hypothesize that a molecular marker for geminivirus resistance can be found within the resistance gene homologues on chromosomes two and eleven. To accomplish our goal we will use a PCR-based tagging method to identify differences in sequences between resistant and susceptible tomato breeding lines. Sequence differences would be indicative of a DNA introgression from a resistant species and could be used as a molecular marker. A successful molecular marker would enable breeders to quickly determine a tomato’s susceptibility or resistance to geminiviruses and greatly aid in the creation of a commercially viable resistant hybrid. Significance and Originality Tomatoes in Central America are plagued by a number of geminiviruses that are transmitted by the whitefly, Bemisia tabaci (Jones, 2003). The effect of these diseases is near total loss of crops (Morales and Anderson, 2001; Nakhla et al., 2004). Lycopersicon hirsutum and Lycopersicon chilense are wild species of tomato that have shown resistance to geminiviruses (Scott et al., 1995; Vidavsky and Czosnek, 1998). However, the shape and size of the plant’s fruits make them unsuitable for commercial use. Breeding programs have been underway for some time with the goal of creating a resistant hybrid plant tha