Résumé
Whereas cross protection was extensively studied and applied in plant protection strategies (PPS) with RNA viruses, this phenomenon was rarely reported with ssDNA viruses of the family Geminiviridae. Using tomato yellow curl virus (TYLCV), a worldwide economically important tomato geminivirus belonging to the genus Begomovirus, we formally demonstrated the existence of cross protection in geminiviruses. When a TYLCV clone is inoculated in susceptible tomato plants already infected with a mutated version of the clone (8 CG deletion in the intergenic region), its accumulation is at least 100 times lower than its accumulation in non-pre-infected plants. The protection effect persists at least two months after superinfection and was also observed in isogenic plants carrying the resistant gene Ty- 1, irrespective of the super-inoculation mode, mediated by agrobacterium or the whitefly vector Bemisia tabaci. As TYLCV is not mechanically transmitted, cross protection is not easily implementable in PPS. However, as of now, it sheds new light on the unusual fitness of TYLCV-IS76, a TYLCV recombinant that easily superinfect TYLCV infected plants in spite of its high nucleotide identity with TYLCV (98 %). Indeed, considering that another TYLCV recombinant, exhibiting the same recombination pattern and the same genetic distance with TYLCV, is unable to establish an infection in tomato plants already infected with TYLCV, TYLCV-IS76 seems to exhibit a cross-protection escape phenotype.