The begomovirus complex infecting tomatoes in Brazil: Characterization, genetic diversity and epidemiology
2009
Murilo, F., Departamento de Fitopatologia, Universidade Federal de Viçosa, MG (Brazil)
Begomoviruses are whitefly-transmitted, singlestranded DNA viruses which cause economically important diseases in several tropical and subtropical areas of the world. Bean golden mosaic caused by BGMV has been reported in Brazil since the 1960's. In spite of decades of research on breeding and disease management, bean golden mosaic continues to limit bean production in the warm and dry areas of the country. The incidence of begomoviruses in tomatoes increased in Brazil after the mid 1990's, following the introduction of the B biotype of Bemisia tabaci ca. 1992. Within a few years, begomoviruses were causing heavy losses in tomato fields all over the country. Work carried out in laboratory focused initially on viral characterization. It was determined that several novel begomovirus species were present in the field, suggesting the transfer of indigenous viruses present in wild hosts to tomatoes by the insect vector. Curiously, the viral species found in tomatoes are not the same normally detected in tomato-associated weeds, suggesting that the viruses undergo a rapid hostadaptation process. It was also found that, over the years, a few species tend to predominate in specific geographical regions. Recent work has been aimed at determining the genetic structure of these different begomovirus populations, in order to understanding the evolutionary forces acting upon the virus, and at studying the spatial-temporal dynamics of begomovirus epidemics in tomatoes. Also, infectious clones corresponding to five of the different viral species, including the three ones which are most prevalent in the field (ToYVSV, ToSRV and ToRMV), have been obtained. These clones can now be used as a useful tool in tomato breeding programs for begomovirus resistance.
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