Resistance to the Insect Vector <i>Bemisia tabaci</i> Enhances the Robustness and Durability of Tomato Yellow Leaf Curl Virus Resistance Conferred by <i>Ty-1</i>

Tomato yellow leaf curl virus (TYLCV) is a begomovirus (genus <i>Begomovirus</i>, family <i>Geminiviridae</i>) transmitted persistently by the whitefly <i>Bemisia tabaci</i>. It causes tomato yellow leaf curl disease (TYLCD), resulting in significant yield losses worldwide. TYLCD is controlled mainly by using F₁ hybrid tomato cultivars harboring the TYLCV resistance gene <i>Ty-1</i>. However, infected <i>Ty-1</i>-bearing tomato plants accumulate viral DNA, which may eventually lead to the emergence of a resistance-breaking TYLCV variant. Recently, a <i>B. tabaci</i>-resistant tomato line derived from the introgression of type IV leaf glandular trichomes and acylsucrose secretion from wild tomato (<i>Solanum pimpinellifolium</i>) was shown to effectively control the spread of TYLCV. In this study, we combined <i>B. tabaci</i> resistance and <i>Ty-1</i>-based TYLCV resistance to increase the robustness and durability of the TYLCD resistance mediated by <i>Ty-1</i> in tomato plants. Specifically, we characterized and used a Group 2-like isolate of the Israel strain of TYLCV (TYLCV-IL-G2) that contributes to TYLCD epidemics in southeastern Spain. A comparison with isolates of the previously identified TYLCV variant revealed TYLCV-IL-G2 has a similar host range, but it induces a slightly more severe TYLCD in <i>Ty-1</i>-bearing tomato plants. Moreover, we demonstrated that acylsucrose-producing <i>B. tabaci</i>-resistant tomato plants can limit the spread of TYLCV-IL-G2 better than a near-isogenic line lacking type IV trichomes and unable to secrete acylsucrose. Pyramiding <i>Ty-1</i>-based TYLCV resistance and <i>B. tabaci</i> resistance provided by type IV glandular trichomes helped to decrease the effects of TYLCV on <i>Ty-1</i>-bearing tomato plants as well as the likelihood of TYLCV evolution in infected plants.