English to Russian Science Genetics virology

From "Risks from GMOs due to Horizontal Gene Transfer", by Paul Keese:
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Most plant viral genes seem to contribute to pathogenicity (Brigneti et al., 1998; Takeshita et al., 2001). Consequently, recombination with a viral transgene could potentially lead to increased virulence. Many plant viral strains can be distinguished by differences in symptom development. New, highly virulent, strains of African cassava mosaic virus ravage a critical African staple in an epidemic that is still expanding (Legg and Thresh, 2000). These new strains, which can overcome previously resistant lines of cassava, have emerged by recombination between viruses naturally co-existing in cassava (Pita et al., 2001; Zhou et al., 1997). In addition, mutation and recombination of viruses in the laboratory have generated offspring viruses with more severe pathology (Ding et al., 1996). However, these novel recombinant viruses have rarely been tested for fitness or competitiveness (Fernandez-Cuartero et al., 1994).
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Новые рекомбинантные вирусы редко исследовались на приспособленность и ... способность конкурировать с другими вирусами?