Résumé
Citrus tristeza virus (CTV) is the most important viral pathogen for citriculture. CTV can infect all species, hybrids and varieties of the family #Rutaceae#. The symptoms are "quick decline" (QD), "vein clearing" (VC), "stem pitting" (SP) and "seedling yellow" (SY). A wide range of strains have been characterized. Symptom intensity depends on the host, the strain, the rootstock and the climate. Corsica, a Mediterranean island where CTV is not endemic, has one of the most important citrus collection in the world and there is special interest and support for phytosanitary controls. This work compares two isolates of CTV: a new isolate (Cal-1) originating from illegally imported ornamental calamondin (#Citrus madurensis# Lour) and the old strain from kumquat (#Fortunella margarita# var 'Marumi'). The two isolates were indexed by inoculation to citrus indicators plants. Serological profiles, dsRNA, coat protein (CP) molecular weight and coat protein gene (CPG) sequence were determined. Isolate Cal-1 presented SP and VC symptoms, while the K strain remained asymptomatic in Mexican Lime. The two isolates presented a 0.5 Kda ds RNA band, which has been related to severity, and the K strain also presented an additional 1.9 Kda band suggesting defective RNAs. Both isolates showed similar serological profiles when exposed to 11 McAbs. The CP was estimated at 26 Kda. The deduced amino acid sequences showed the MCA 13 antibody recognition epitope for both isolates. Isolate Cal-1 was determined as being a strain having moderate to severe characteristics. The K strain was reaffirmed as being an asymptomatic strain on Mexican Lime, but could not be distinguished from severe strains by serological and/or molecular markers characteristics. These results demonstrate that ornamental citrus are high risk CTV strain reservoirs due to their possible dispersion to surrounding commercial citrus orchards. (Résumé d'auteur)