Distribution and genetic diversity of tomato-infecting begomoviruses in Brazil *

Abstract

Tomato-infecting begomoviruses have been reported throughout Brazil since the introduction of the B biotype of Bemisia tabaci. Here, we report a large scale survey on the distribution and genetic diversity of tomato-infecting begomoviruses. Tomato samples with typical begomovirus symptoms were collected in seven different states, comprising the major tomato growing areas of the country. Viruses were detected by polymerase chain reaction (PCR) using universal primers for the genus Begomovirus. PCR-amplified fragments were cloned and sequenced. Based on sequence comparisons and phylogenetic analyses, at least seven previously undescribed species of begomoviruses were found. Four of the new viruses were found exclusively in the Southeastern states, two exclusively in the Northeastern states, and one was found in both regions. Sequence comparisons reveal strong evidence of recombination among the Brazilian begomoviruses. Together, the results indicate the existence of a high degree of pre-existing genetic diversity among tomato-infecting begomoviruses in Brazil and suggest that these viruses have emerged after being transferred from natural hosts to tomatoes, due to the introduction into Brazil of a novel polyfagous biotype of the whitefly vector.

Microsatellites reveal extensive geographical, ecological and genetic contacts between invasive and indigenous whitefly biotypes in an insular environment

“…Other introductions of the B biotype have had different outcomes : in Spain, the indigenous Q biotype coexists with B but has remained predominant in the field (Pascual & Callejas, 2004). However, whether the B biotype displaced or simply coexists with indigenous ones, new begomovirus epidemics have been reported (Polston & Anderson, 1997 ;Ribeiro et al, 2003). Many questions remain disputed with regard to the exact nature of biotypes, especially their degree of genetic isolation and whether interbreeding occurs when two of them are brought into sympatry.…”

Tomato yellow vein streak virus: relationship with Bemisia tabaci biotype B and host range

“…ToYVSV presence was also confirmed in groups of aleyrodids that fed on the various plant species used as sources of inoculum (data not presented). These results demonstrate the importance of eliminating these plant species from the surroundings of new crops, because they could serve as reservoirs of the virus not only for tomato, but also for potato and green pepper crops, where ToYVSV has been previously found (Souza-Dias et al, 1996;Nozaki, 2006;Ribeiro et al, 2006).…”

“…In tomato plants cultivated under plastic greenhouse conditions the incidence of ToYVSV ranged from 4.8% to 69.3%, depending on the planting season (Vecchia et al, 2007). This virus has also been previously reported to infect green pepper (Capsicum annuum) (Nozaki, 2006) and potato (Solanum tuberosum) (Ribeiro et al, 2006;Souza-Dias et al, 1996).…”

“…amaranticolor, C. quinoa, D. stramonium, G. globosa, N. clevelandii and N. tabacum cv. TNN were identified as susceptible to ToYVSV (Table 4) (Ribeiro et al, 2006). Although these two isolates were only transmitted by B. tabaci biotype B, Colariccio et al (2007) reported the mechanical transmission of a ToYVSV isolate from Monte Mor, SP, Brazil, from tomato to tomato cv.…”

“…Recent studies on molecular characterization of begomoviruses infecting tomato plants (Solanum lycopersicon) indicated the existence of a complex diversity of species in Brazil (Ambrozevícius et al, 2002;Ribeiro et al, 2003), resulting from the introduction and dispersal throughout the country of the effective vector Bemisia tabaci biotype B since the 1990's (Lourenção & Nagai, 1994;França et al, 1996). Currently, this complex comprises four recognized species, at least eight other potential species, including Tomato yellow vein streak virus (ToYVSV) (Colariccio et al, 2007), and some recombinant forms of this virus, which have not been properly characterized (Ambrozevícius et al, 2002;Calegario et al, 2007;Fernandes et al, 2008).…”