Coexistência e evolução molecular de populações de begomovírus na planta não-cultivada Sida acuta

• Autor(a) principal: Godinho, Márcio Tadeu
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1064
• topic: Begomovirus; Evolução; Geminiviridae; Nova espécie; Begomovirus; Evolution; Geminiviridae; New species; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

The Geminiviridae family includes viruses with genomes consisting of one or two molecules of single-stranded circular DNA, encapsidated by a single structural protein in twinned icosahedral particles. The family includes seven genera defined based on the type of insect vector, host range, genome organization and phylogenetic relationships. Viruses belonging to the genus Begomovirus have one or two genomic components, are transmitted by the whitefly Bemisia tabaci and infect dicotyledonous plants. The occurrence of begomoviruses in cultivated and non-cultivated plants has been reported in Brazil since the 1950s, initially in malvaceous and leguminous hosts, and since the mid-1990s, following the introduction of the B biotype of B. tabaci, also in solanaceous hosts. Several studies have been conducted to characterize the begomoviruses occurring in tomato and bean crops in Brazil, and to evaluate the genetic variability of viral populations in cultivated plants. Studies determining the genetic structure and population dynamics of begomoviruses in non-cultivated hosts are less frequent, although it is accepted that these hosts act as a source of inoculum, and thus may contribute to epidemics in cultivated hosts. This study aimed to characterize and study the genetic variability of begomoviruses infecting the non-cultivated plant Sida acuta, sampled in an area of 10,000 m2. The results showed a high variability among isolates, with the detection of three new begomovirus speceis whose proposed names are Sida acuta mosaic virus (SAMV), Sida golden yellow mosaic virus (SiGYMV) and Sida yellow spot virus (SiYSV). The SAMV population is subdivided into three different strains (S1/S2/S3), with point mutations in the CP and Rep viii genes separating the three strains, and with a possible phenotypic difference between strains S1 and S2. Even in the small sampled area, several plants had mixed infection and pseudorecombination between the different strains. The clones belonging to the species SiGYMV and SiYSV have a genomic organization related to begomoviruses present in the "Old World" (Europe, Asia and Africa), with the presence of an AV2-like ORF present only in begomovirus from that region, and with conserved motifs in the CP and Rep proteins also existing only in the Old World. Thus, the high species diversity and genetic variability of begomoviruses can be sampled even in small areas.