Tomato Yellow Leaf Curl Sardinia Virus, a Begomovirus Species Evolving by Mutation and Recombination: A Challenge for Virus Control

The tomato leaf curl disease (TYLCD) is associated with infections of several species of begomoviruses (genus Begomovirus, family Geminiviridae) and causes severe damage to tomatoes throughout tropical and sub-tropical regions of the world. Among others, the Tomato yellow leaf curl Sardinia virus (TYLCSV) species causes damage in the Mediterranean Basin since early outbreaks occurred. Nevertheless, scarce information is available about the diversity of TYLCSV. Here, we study this aspect based on the sequence information accessible in databases. Isolates of two taxonomically differentiated TYLCSV strains can be found in natural epidemics. Their evolution is mostly associated with mutation combined with selection and random genetic drift and also with inter-species recombination which is frequent in begomoviruses. Moreover, a novel putative inter-strain recombinant is reported. Although no significantly new biological behaviour was observed for this latter recombinant, its occurrence supports that as shown for other related begomoviruses, recombination continues to play a central role in the evolution of TYLCD-associated viruses and the dynamism of their populations. The confrontation of resistant tomatoes with isolates of different TYLCD-associated viruses including the novel recombinant demonstrates the existence of a variable virus x plant genotype interaction. This has already been observed for other TYLCD-associated viruses and is a challenge for the control of their impact on tomato production.