OCCURRENCE, DISTRIBUTION, CHARACTERIZATION OF CITRUS TRISTEZA VIRUS AND ITS VECTORS IN SYRIA

Syrian citrus growing areas (Lattakia and Tartous) were surveyed to assess the distribution of Citrus tristeza virus (CTV) and its vectors. Eight nurseries, two bud-wood source fields and 19 groves of the main citrus varieties were visually inspected and sampled for laboratory analysis. A total of 89 CTV-infected plants out of 2653 were identified by DTBIA in two nurseries, two bud-wood source fields and six groves. Based on the reaction with several monoclonal antibodies (MAbs), CTV isolates clustered in 4 serogroups. Only one CTV strain from the sweet orange of cv. Valencia induced severe symptoms on Mexican lime seedlings by graft-transmissions. Hybridization of PCR amplicons from the coat protein gene with a set of strain-specific probes revealed a complex strain mixture. Aphis spiraecola (50%) and A. gossypii (27%) were the most common aphids, whereas no evidence for the presence of Toxoptera citricidus was found.