Genetic variability of Euphorbia yellow mosaic virus and Macroptilium yellow vein virus in their respective natural hosts, Euphorbia heterophylla and Macroptilium lathyroides

Begomoviruses (genus Begomovirus, family Geminiviridae) comprise a group of plant viruses of great economic importance causing serious economic losses in tropical and subtropical crops. It is believed that the emergence of begomoviruses in Brazil occurred through horizontal transfer of viruses previously restricted to non-cultivated plants by the B biotype of Bemisia tabaci. Little is known about the genetic variability of weedinfecting begomoviruses. The study of this variability is important to understand how viruses evolve in order to adopt strategies for the development of crop cultivars with durable resistance. In this study we investigated the genetic variability of two weedinfecting begomoviruses, Euphorbia yellow mosaic virus (EuYMV) and Macroptilium yellow vein virus (MaYVV), which infect Euphorbia heterophylla and Macroptilium lathyroides, respectively. Our results, based on 19 DNA-A sequences of EuYMV and 18 of MaYVV obtained from samples collected in 2011 and 2012, support the hypothesis that the genetic structure of begomoviruses can be modulated by their hosts by common processes of selection, mutation and recombination. We observed distinct degrees of genetic variability between the two viruses. EuYMV presented a higher variability, similar to other weed-infecting begomoviruses, while MaYVV presented a lower variability. The nucleotide diversity of EuYMV (0.00819) was four-fold higher than that of MaYVV (0.00197). The mutation frequency of EuYMV (2.5×10-3) was higher than that of MaYVV (4.2×10-4). This difference was supported by the higher nucleotide diversity of all genes of EuYMV compared to MaYVV: CP (~three-fold), Rep (~seven-fold), Trap (~32-fold), Ren (~four-fold), AC4 (~eight-fold). Therefore the higher variability of EuYMV can be explained mostly by the Trap gene. The lower diversity observed for MaYVV could be due to its recent emergence compared to EuYMV, reported since the 1950 s in Brazil. %%%%Os begomovirus (genero Begomovirus, familia Geminiviridae) sao um grupo virus de plantas de grande importância economica causando serias perdas em diversas culturas tropicais e subtropicais. Acredita-se que a emergencia dos begomovirus presentes no Brasil se deu por meio da transferencia horizontal de virus anteriormente restritos a plantas silvestres e invasoras para plantas cultivadas mediada pelo biotipo B de Bemisia tabaci. A maioria dos trabalhos realizados ate o presente tiveram enfoque na caracterizacao molecular dos begomovirus e pouco se sabe sobre a variabilidade genetica das populacoes destes no campo. O estudo desta variabilidade e importante para entender como os virus evoluem no sentido de serem adotadas estrategias para o desenvolvimento de cultivares com resistencia duravel. Neste trabalho foi investigada a variabilidade genetica de dois begomovirus encontrados em plantas invasoras, Euphorbia yellow mosaic virus (EuYMV) e Macroptilium yellow vein virus (MaYVV), que infectam Euphorbia heterophylla e Macroptilium lathyroides, respectivamente. Os resultados, baseados em 19 sequencias de…