DETECTION OF CITRUS TRISTEZA VIRUS AND CITRUS VIROID SPECIES IN JAMAICA

Abstract

Field surveys for Citrus tristeza virus (CTV) and citrus viroids were conducted in the six major citrus producing regions across Jamaica. A total of 57 samples were tested by double antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISA) for CTV and reverse transcription polymerase chain reaction (RT-PCR) for CTV and citrus viroids. DAS-ELISA revealed an overall CTV infection of 30-100%, with incidences of severe strains at 50-100%. RT-PCR detected CTV in 10-75% of the samples, while 9-67% were infected with at least two viroid species. Citrus viroids of four groups were prevalent including Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd), the causal agents of exocortis and cachexia diseases, respectively. Overall, CTV incidence was higher than that of the citrus viroids, except in one region where the incidence of CEVd was higher. Biological indexing confirmed the presence of viroids and mild, decline and stem pitting CTV strains; additionally, mixed infections with CTV strains (13%) and CTV with viroid infections (53%) were observed. Nucleotide sequencing of the CTV coat protein gene and viroid genome sequences isolated from these samples indicated high identities among some of the Jamaican isolates and previously reported CTV and citrus viroid isolates from Central and North America and Eurasia (90-100%, 39-100%, respectively). The findings suggest the need for appropriate certification programmes and management practices to mitigate the impact of both pathogens on the citrus industry.