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The non-canonical tomato yellow leaf curl virus recombinant that displaced its parental viruses in Southern Morocco exhibits a high selective advantage in experimental conditions

Belabess Z., Peterschmitt M., Granier M., Tahiri A., Blenzar A., Urbino C.. 2016. Journal of General Virology, 97 (12) : p. 3433-3445.

DOI: 10.1099/jgv.0.000633

Recombination events are frequently inferred from the increasing number of sequenced viral genomes, but their impact on natural viral populations has rarely been evidenced. TYLCV-IS76 is a recombinant (Begomovirus,Geminiviridae) between the Israel strain of tomato yellow leaf curl virus (TYLCV-IL) and the Spanish strain of tomato yellow leaf curl Sardinia virus (TYLCSV-ES) that was generated most probably in the late 1990s in southern Morocco (Souss). Its emergence in the 2000s coincided with the increasing use of resistant tomato cultivars bearing the Ty-1 gene, and led eventually to the entire displacement of both parental viruses in the Souss. Here, we provide compelling evidence that this viral population shift was associated with selection of TYLCV-IS76 viruses in tomato plants and particularly in Ty-1-bearing cultivars. Real-time quantitative PCR (qPCR) monitoring revealed that TYLCV-IS76 DNA accumulation in Ty-1-bearing plants was significantly higher than that of representatives of the parental virus species in single infection or competition assays. This advantage of the recombinant in Ty-1-bearing plants was not associated with a fitness cost in a susceptible, nearly isogenic, cultivar. In competition assays in the resistant cultivar, the DNA accumulation of the TYLCV-IL clone ¿ the parent less affected by the Ty-1 gene in single infection ¿ dropped below the qPCR detection level at 120 days post-infection (p.i.) and below the whitefly vector (Bemisia tabaci) transmissibility level at 60 days p.i. The molecular basis of the selective advantage of TYLCV-IS76 is discussed in relation to its non-canonical recombination pattern, and the RNA-dependent RNA polymerase encoded by the Ty-1 gene.

Mots-clés : géminivirus enroulement jaune tomat; résistance génétique; recombinaison; pcr; adn recombiné; solanum lycopersicum; virus des végétaux; begomovirus; maroc; france; tomato yellow leaf curl virus; Émergence

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