An efficient in vitro-inoculation method for Tomato yellow leaf curl virus

A TYLCV isolate was cloned, sequenced and used to construct a 1.8-mer infectious clone. Three weeks old microshoots of TYLCV-susceptible tomato plants were inoculated with Agrobacterium tumefaciens harboring the infectious clone for the TYLCV isolate. After two weeks, the TYLCV symptoms started to appear on the in vitro-inoculated plants and the symptoms became more severe and pronounced eight weeks post-inoculation. The method was used efficiently to uncover the resistance mechanism against TYLCV in Solanum habrochaites accession LA 1777, a wild tomato known for its high resistance to whitefly and TYLCV.The reported in vitro-inoculation method can be used to screen tomato genotypes for their responses to TYLCV under controlled conditions and it will be a useful tool for better understanding of the TYLCV biology in tomato plants.Since it was first reported in the Jordan valley [1], the tomato yellow leaf curl disease (TYLCD), caused by the Tomato yellow leaf curl virus (TYLCV) and related viruses, has become a serious problem that affects tomato (Solanum lycopersicum) worldwide. TYLCV is a member of the family Geminiviridae, genus Begomovirus and it is transmitted to tomato by the whitefly Bemisia tabaci in a persistent and circulative manner [2]. The management of the disease in tomato production areas is difficult and expensive and the control measurements are focused mainly on the whitefly control and are based on insecticide treatments and/or the use of physical barriers [3].One of the best ways to reduce TYLCV damage is to breed plants resistant to both the virus and the vector. Breeding programs for TYLCV-resistant cultivars are based on the transfer of TYLCV resistance genes from wild tomato species into cultivated tomato [4]. Previous studies have revealed the presence of resistance mechanisms against the virus in wild tomato species that are controlled by multiple genes [4-6]. For instance, the TYLCV resistance in S. chilense is controlled by a major gene,