Deep sequencing and analysis of small RNAs in sweet orange grafted on sour orange infected with two citrus tristeza virus isolates prevalent in Sicily.

Two representative isolates of a citrus tristeza virus population in Sicily, SG29 (aggressive) and Bau282 (mild), were sequenced via viral small RNAs (vsRNA) produced in budlings of sweet orange grafted on sour orange. Phylogenetic relationships with Mediterranean and exotic isolates revealed that SG29 clustered within the "VT-Asian" subtype, whereas Bau282 belonged to the cluster T30. The study confirms that molecular data need to be integrated with bio-indexing in order to obtain adequate information for risk assessment.