Genomic Variability of Citrus tristeza virus (CTV) Isolates Introduced into Morocco

Bouabid Lbida, F. Fonseca, C. Santos, M. Zemzami, A. Bennani, G. Nolasco


Genomic variability of the coat protein gene of Citrus tristeza virus isolates obtained from old Meyer
lemon introductions in Morocco and more recent budwood introductions from Spain were studied. The coat protein
gene of the virus was amplified directly from infected tissue by immunocapture RT-PCR and analysed by single
stranded conformation polymorphism (SSCP) and sequencing. Each isolate consisted of several related genomic
variants, typical of a quasi-species. Although SSCP analysis has only limited typing ability it could be used in an
initial screening to discriminate between isolates of different origin and to analyse the genomic structure of each
isolate. Sequence analysis showed that the isolates of Spanish origin were closely related to mild isolates characterised
in Florida and in Portugal. The Meyer lemon isolate on the other hand was related to severe strains of Meyer
lemon characterised in Florida some years ago and to other severe strains from Brasil. A knowledge of the coat
protein gene sequence is useful to trace the origin of the isolates.

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