Variabilidade e estrutura genética do Begomovírus Euphorbia yellow mosaic vírus infectando hospedeiros não-cultivados no Brasil

Abstract

The begomoviruses are among the most economic important pathogens worldwide, affecting different crops, mainly in tropical and subtropical regions. In Brazil, besides cultivated plants belonging to the genus Phaseolus (beans) and tomato (Solanum lycopersicum), begomoviruses infect non-cultivated hosts in different botanical families: Malvaceae, Euphorbiaceae, Fabaceae and Asteraceae. These viruses can be transmitted between different cultivated and non-cultivated hosts, with wild plants acting as putative source of inoculum and as alternate hosts, displaying epidemiological importance in the disease cycle. The aim of this study was to quantify the different evolutionary mechanisms acting on the variability and genetic structure of begomovirus populations infecting non-cultivated hosts in Brazil. Plants from the family Euphorbiaceae showing symptoms of begomovirus infection were collected in the Paraíba State, total DNA was extracted and viral genomic components were amplified by RCA, cleaved with restriction enzymes, cloned and sequenced. The sequences from this study were compared to sequences from the Genbank non-redundant nucleotide database, taking account the criterion of ≥91% for species demarcation. Phylogenetic, diversity, recombination and selection analyses were performed. The pairwise comparison showed that all 49 isolates used in this study belonged to one only viral species: Euphorbia yellow mosaic virus (EuYMV). Phylogenetically, the population grouped in very similar trees, but with some topological inconsistencies for the different genomic regions. Formation of two main groups correlated with geographic origin was observed. Nucleotide diversity of the total population was higher than Northeastern and Midwestern subpopulations, being similar in the DNA-A, CP and Rep datasets. Network analysis of the DNA-A, CP and Rep datasets showed evidence of recombination affecting the evolution of isolated from Northeastern and Midwestern, being detected only one isolate as putative recombinant, with recombination breakpoints in the Common Region and interface of the Trap and Ren genes. Selection analysis showed that negative selection pressure or purifying selection is the main selection force acting on CP and Rep of the EuYMV subpopulations.