ABSTRACT
Citrus tristeza virus (CTV) causes significant yield losses to sweet orange [Citrus sinensis (L.) Osbeck] and its control has been carried out especially with premunization. The aim of this study was to analyze the variability of severe and mild CTV isolates from citrus plants inoculated and kept in a greenhouse and field samples collected from a commercial orchard located in the city of Rolândia, Paraná State (PR). To determine the variability and the genetic diversity of isolates, symptoms were evaluated and the techniques RT-PCR and RFLP were employed, using the specific oligonucleotides HCP1 / HCP2 and subsequent sequencing of the amplified fragments. In the evaluation of stem pitting, the isolates kept in greenhouse induced mild symptoms, except for the severe isolate Capão Bonito. The most severe symptoms occurred in samples located in the field. The multivariate analyses showed that CTV isolates tend to cluster according to the severity of symptoms and the environmental conditions to which they were exposed, forming distinct groupings among samples from the field and the greenhouse. The dendrogram generated from the sequencing of isolates and the multivariate analyses revealed that the isolate from the sample “Forte Arapongas” presented greater similarity with the severe pattern control from Capão Bonito. The isolates identified as mild and from the samples Pêra IAC and Rolândia 5 presented greater similarity. Host plants maintained in the field can be considered to have more variability of isolates.
Keywords
Citrus; stem pitting; genetic diversity; mild isolate; severe isolate
