Tomato Yellow Leaf Curl Virus

The name tomato yellow leaf curl virus (TYLCV) was coined in the late 1950s to describe a virus infecting tomato plants in the Middle East. To date, TYLCV can be found in the entire Middle East, Central Asia, North and West Africa, Southeast Europe, the Caribbean Islands, and Southeast USA. TYLCV is a member of the genus Begomovirus of the family Geminiviridae. It is transmitted in nature by the whitefly Bemisia tabaci. It has a circular single-stranded DNA genomic molecule of 2787 nt encapsidated in a 20 × 30 nm geminate particle. In the field tomato plants become infected almost immediately after transplanting and fail to yield, causing important economical loss. The virus is mostly phloem limited. TYLCV is transmitted by its vector in a circulative manner. It has deleterious effects on its animal host, decreasing life expectancy and fertility, and invading the reproductive system. Breeding programs based on the introgression of resistance from wild tomato species have produced varieties with adequate resistance. Several loci tightly linked to TYLCV resistance have been assigned to the small arm of tomato chromosome 6. Tomato plants with various levels of resistance have been genetically engineered by expressing functional as well as dysfunctional viral genes, and by antisense RNA and post-translational gene-silencing strategies.