LAUSR

The tomato yellow leaf curl disease (TYLCD) causes severe damage to tomato crops in warm regions of the world associated with infections of several whitefly (Bemisia tabaci)-transmitted single-stranded (ss) DNA begomoviruses (genus Begomovirus, family Geminiviridae). The most widespread begomovirus isolates associated with TYLCD are those of the type strain of the Tomato yellow leaf curl virus species, known as Israel (TYLCV-IL). The Ty-1 gene is widely used in commercial tomato cultivars to control TYLCV-IL damage providing resistance to the virus by restricting viral accumulation and tolerance to TYLCD by inhibiting disease symptoms. However, several reports suggest that TYLCV-IL-like isolates are adapting to the Ty-1 gene and are cause of concern for possible overcoming of the control provided. This is the case of TYLCV-IL IS76-like recombinants that have a small genome fragment acquired by genetic exchange from an isolate of Tomato yellow leaf curl Sardinia virus, another begomovirus species associated with TYLCD. Here we showed that TYLCV-IL IS76-like isolates partially break down the TYLCD-tolerance provided by the Ty-1 gene and that virulence differences might exist between isolates. Interestingly, we demonstrate that mixed infections with an isolate of the crinivirus (genus Crinivirus, family Closteroviridae) species Tomato chlorosis virus (ToCV), a ssRNA virus also transmitted by B. tabaci emerging worldwide in tomato crops, boost the breakdown of the TYLCD-tolerance provided by the Ty-1 gene either with TYLCV-IL IS76-like or canonical TYLCV-IL isolates. Moreover, we demonstrate the interest of incorporating the Ty-2 gene in Ty-1-commercial tomatoes to restrict (no virus or virus, ....