**9. Conclusions**

*Citrus tristeza virus* research continues pushing the molecular virology technology to further limits. Molecular tools have been developed to study CTV gene expression, replication, assembly, systemic infection, viral movement, and plant-host interactions. The scientific results reveal a virus with a complex genetics that has become a model for molecular virology studies and viral biotechnology development. However, in spite of the CTV complicated genetics, further efforts need to be applied to engineer viral-based vectors, or additional biotechnological approaches, with the aim of understanding the mechanisms of viral move‐ ment, pathogenesis, resistance and aphid transmission, and the role of the D-RNAs in the CTV infection or the pathogenesis process. This valuable information will be applied to implement biotechnological strategies in order to control the devastating CTV epidemics.

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