Tomato yellow leaf virus (TYLCV): The structure, ecotypes and the resistance germplasm resources in tomato
Tomato yellow leaf virus (TYLCV) transmitted by the whitefly are a group of geminiviruses, which can cause large economic loses. The genome of TYLCV contains six partially overlapping open reading frames (ORFs) bidirectionally arranged into two transcriptional units that are separated by an intergenic region (IR). The TYLCV can be classified into three main groups, the Mediterranean/Middle East/African region group, India, the Far East and Australia group and the America group. However, due to globalization and the recombination of different viruses in the recent years, the speed of emergence of the novel viruses becomes more and more rapid. The initial tomato cultivars were extremely susceptible to TYLCV. For the overwhelming viruses, the breeding research is yet to be done. Many TYLCV resistance germplasms were collected and indentified in the Lycopersicon section species for breeding new cultivars in the last decades, especially in Solanum pimpinellifolium, Solanum peruvianum, Solanum chilense, Solanum habrochaites and Solanum cheesmaniae. In these germplasms, several resistance QTLs and related molecular markers were found and developed to benefit the TYLCV resistance breeding research and some new cultivars were already bred in commercial areas.
Key words: Tomato yellow leaf curl virus (TYLCV), germplasm, resistance, breeding