The NLR Protein Encoded by the Resistance GeneTy-2Is Triggered by the Replication-Associated Protein Rep/C1 of Tomato Yellow Leaf Curl Virus

The whitefly-transmitted tomato yellow leaf curl virus (TYLCV) is one of the most destructive viral pathogens of cultivated tomato. To combat TYLCV, resistance geneTy-2has been introduced into cultivated tomato (Solanum lycopersicum) from wild tomato speciesSolanum habrochaitesby interspecific crossing. Introgression lines withTy-2contain a large inversion compared withS. lycopersicum, which causes severe suppression of recombination and has hampered the cloning ofTy-2so far. Here, we report the fine-mapping and cloning ofTy-2using crosses between aTy-2introgression line and several susceptibleS. habrochaitesaccessions.Ty-2was shown to encode a nucleotide-binding leucine-rich repeat (NLR) protein. For breeding purposes, a highly specific DNA marker tightly linked to theTy-2gene was developed permitting marker-assisted selection. The resistance mediated byTy-2was effective against the Israel strain of TYLCV (TYLCV-IL) and tomato yellow leaf curl virus-[China : Shanghai2] (TYLCV-[CN : SH2]), but not against tomato yellow leaf curl Sardinia virus (TYLCSV) and leafhopper-transmitted beet curly top virus (BCTV). By co-infiltration experiments we showed that transient expression of the Rep/C1 protein of TYLCV, but not of TYLCSV triggered a hypersensitive response (HR) inNicotiana benthamianaplants co-expressing theTy-2gene. Our results indicate that theRep/C1gene of TYLCV-IL presents the avirulence determinant ofTy-2-mediated resistance.