Further characterization of tomato-infecting begomoviruses in Brazil

Abstract

Tomato cultivation in Brazil is threatened by a number of tomato-infecting viruses belonging to the genus Begomovirus of the family Geminiviridae. Here, we report the full DNA-A sequences of three Brazilian begomoviruses: a potentially new tomato-infecting viruses, tomato interveinal chlorosis virus (ToICV), and two previously proposed begomoviruses for which only partial DNA-A sequences are available in the databases: tomato mottle leaf curl virus (TMoLCV) and tomato golden vein virus (TGVV). The complete sequences of the DNA-B components of TMoLCV and TGVV and the DNA-A components of a number of tomato severe rugose virus variants are also presented. Collectively, all of the analyzed sequences were phylogenetically clustered within the two major groups of Brazilian tomato-infecting begomoviruses.

Brazilian Begomovirus Populations Are Highly Recombinant, Rapidly Evolving, and Segregated Based on Geographical Location

“…Even though we have not performed infectivity studies comparing these viruses, it is reasonable to assume that the viruses in these three clusters are well adapted to cultivated plants, as ToCMoV, ToSRV, and ToYVSV were the species most frequently detected both here (Table 1) and in other studies (21,24,59), and Soybean blistering mosaic virus (SoBlMV) is widespread in soybean fields in northwestern Argentina (60). Although detected in only a small number of samples here, another member of this group, TMoLCV, is widespread in tomato fields in the Brazilian northeast (23).…”

“…In Brazil, 11 begomovirus species, all of which have been found only in that country, are currently known to infect tomatoes naturally in the field: Tomato golden mosaic virus (TGMV) (17), Tomato rugose mosaic virus (ToRMV) (18), Tomato chlorotic mottle virus (ToCMoV) (19), Tomato yellow spot virus (ToYSV) (20), Tomato severe rugose virus (ToSRV) (21), Tomato common mosaic virus (ToCmMV), Tomato mild mosaic virus (ToMlMV) (15), Tomato yellow vein streak virus (ToYVSV) (22), Tomato interveinal chlorosis virus (ToICV), Tomato mottle leaf curl virus (TMoLCV), and Tomato golden vein virus (TGVV) (23). At least seven additional genetically distinct begomoviruses have been associated with diseases of tomato, but these viruses have not been completely characterized and their role in the etiology of these diseases remains to be established (10,24,25).…”

RNA de interferência como estratégia para controle de begomoviroses

“…Doenças causadas por begomovírus representam um importante problema para a produção de tomate no Brasil e no mundo (Varma and Malathi, 2003) (Fernandes et al, 2008) (Albuquerque et al, 2012). Estratégias para controle desses vírus baseiam-se principalmente no controle do vetoratravés da aplicação de inseticidas tóxicos, que geram problemas ambientais e seleção de insetos resistentes (Dalton, 2006) -aliado a técnicas de manejo no campo, como a eliminação de plantas infectadas e a criação de períodos de vazio sanitário, que não são totalmente efetivas, uma vez que diversas plantas daninhas funcionam como potenciais reservatórios e fontes de inóculo de diferentes espécies desses vírus (Barbosa et al, 2009) (Barreto et al, 2013).…”

“…Essa cultura sofre infecção de uma variedade de espécies desses vírus (Fernandes et al, 2008) (Albuquerque et al, 2012), o que torna a resistência de amplo espectro um desafio. Diante disso, foi desenvolvido um cassete de interferência quimérico, que expressa um hpRNA, que tem como alvo sequências conservadas do gene repfundamental para a replicação viral -de distintas espécies de begomovírus, e sua habilidade no silenciamento desses agentes foi avaliada em plantas transgênicas de Nicotiana benthamiana.…”

“…Esses agentes apresentam alta variabilidade genética e se adaptaram a essa cultura rapidamente via eventos de recombinação (Ribeiro et al, 2003) . De acordo com Brown et al (2015), atualmente existem pelo menos 16 espécies de begomovírus associados a tomateiro no Brasil: Tomato golden mosaic virus (Maytis et al, 1975), Tomato rugose mosaic virus (Fernandes et al, 2006), Tomato chlorotic mottle virus (Ribeiro et al, 2007), Tomato yellow spot virus (Calegario et al, 2007), Tomato severe rugose virus (Fernandes et al, 2008), Os vírus tomato severe rugose virus (ToSRV), tomato golden vein virus (TGVV), tomato common mosaic virus (ToCmMV), tomato chlorotic mottle virus (ToCMoV) e tomato yellow vein streak virus (ToYVSV) são os agentes predominantes nas principais áreas produtoras do país (Fernandes et al, 2008) (Albuquerque et al, 2012) (Barbosa et al, 2015). No entanto, as populações de begomovírus ao longo do tempo demonstram alta…”