Toward Fine Mapping of the Tomato Yellow Leaf Curl Virus Resistance Gene Ty-2 on Chromosome 11 of Tomato

The whitefly-transmitted Tomato yellow leaf curl virus (TYLCV) is a major pathogen of tomatoes grown in tropical and subtropical regions of the world. Several genes of different origins conferring resistance to TYLCV have been introgressed to the cultivated tomato ( Solanum lycopersicum ), including the single dominant gene, Ty-2 , that originated from S. habrochiates and was previously mapped to a 19-cM region on the long arm of chromosome 11 delimited by restriction fragment length polymorphism markers TG36 and TG393. In the present study, we confirmed the dominant inheritance of the Ty-2 gene from TYLCV evaluation and molecular marker analysis of an F 2 segregating population derived from a commercial hybrid that carries the Ty-2 gene. Evaluating recombinants recovered from the F 2 progeny for TYLCV resistance localized the Ty-2 gene to a marker interval of 5.5 cM between C2_At1g07960 (82.5 cM) and C2_At4g32930 (88 cM). Additional recombinants were identified for the target region carrying the Ty-2 gene. TYLCV evaluation of the progeny from these recombinants further delimited the Ty-2 gene to a 4.5-cM interval between C2_At1g07960 (82.5 cM) and cLEN-11-F24 (87 cM). The smaller introgressions no longer include the fusarium wilt race 2 resistance locus ( I -2), which should facilitate combining the two resistance genes in cis configuration. The polymerase chain reaction-based markers developed from the present study can be used to precisely monitor the introgression of the Ty-2 gene, thus offering the opportunity to pyramid TYLCV resistance genes from different sources as well as resistance genes for other pathogens into elite tomato cultivars.