DIVERSIDADE GENÉTICA E EVOLUÇÃO DE BEGOMOVÍRUS EM TOMATEIRO

Abstract

Viruses belonging to the family Geminiviridae are transmitted in nature by vector insects to a wide range of mono and dicotyledonous hosts. The family has a monopartite or bipartite genome of single-stranded circular DNA, encapsidated into two twinned particles with incomplete icosahedral format. Depending on the insect vector, hosts, genomic organization and phylogenetic relationship, the family is divided into seven genera: Begomovirus, Mastrevirus, Curtovirus, Topocuvirus, Becurtovirus, Turncurtovirus and Eragrovirus. The genus Begomovirus has the highest number of species and, in Brazil, begomoviruses are among the main diseases of tomato. The species of this genus are transmitted naturally by the whitefly Bemisia tabaci MEAM 1 (Middle East Asia Minor 1), and currently sixteen species are recognized infecting tomato in Brazil, being Tomato severe rugose virus (ToSRV) the prevalent species. Studies on genetic diversity were then conducted, with the presence of three species, ToSRV, Tomato mottle leaf curl virus (ToMoLCV) and Tomato common mosaic virus (ToCmMV) in single or mixed infection in the states of Goiás and Rio de Janeiro. The results demonstrate that ToSRV is prevalent in single infections and may also occur in mixed infections with ToMoLCV and ToCmMV in Goiás and Rio de Janeiro, respectively. ToSRV is the most important species for tomato, considering its incidence in the state of Goiás. In order to understand its population genetic structure, 61 ToSRV isolates (component DNA-A) obtained from different municipalities of the state of Goiás, Brazil, in the years 2003, 2008 and 2015 were analyzed. Especially for begomoviruses, genetic variability has been shown to be important for viral adaptation. Interestingly, the results presented here demonstrate low values of genetic differentiation between isolates from different locations and/or collection years, suggesting the existence of a single viral and genetically stable population. Genetic recombination does not seem to be important for the species, and mutation seems to be the main mechanism responsible for genetic variability, even in low values.