Pyramiding Ty-1/Ty-3 and Ty-2 in tomato hybrids dramatically inhibits symptom expression and accumulation of tomato yellow leaf curl disease inducing viruses

Tomato yellow leaf curl disease is a major constraint for tomato production worldwide and availability of new resistant materials is of great importance for breeding programmes. A phenotypic survey was undertaken to evaluate the level of resistance to the main tomato yellow leaf curl disease-inducing viruses Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus, in several commercial tomato cultivars, never characterised before. Seven weeks post inoculation, two cultivars resulted in high resistant phenotypes to both begomoviruses, and four were tolerant to at least one of them. In the two highly resistant hybrids (SJ12, RFT112), symptoms were completely absent and viral DNA was from 102to 105fold lower than in susceptible plants. Molecular marker analysis revealed that these genotypes harbour the resistant genes Ty-1/Ty-3 and Ty-2. Given their high resistance, they can be considered good candidates for cultivation and breeding in areas where incidence of TYLCD is very elevated.