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

Abstract

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 F2 segregating population derived from a commercial hybrid that carries the Ty-2 gene. Evaluating recombinants recovered from the F2 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.