Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2005
Publication Date: 6/1/2006
Citation: Melzer, M., Borth, W., Zee, F., Garnsey, S., Hilf, M.E., Hu, J. 2006. Incidence and diversity of citrus tristeza virus in hawaii. Phytopathology. 96:S77. Interpretive Summary: Citrus tristeza virus is the cause of the most destructive virus disease of citrus, and is found in US citrus areas, including Hawaii. Understanding the distribution and genetic variation of the virus population in Hawaii can provide information on potential disease development in existing and future citrus plantings, so that control or regulatory procedures can be implemented.
Technical Abstract: Citrus tristeza virus (CTV), the causal agent of quick decline and stem pitting in citrus, and its most effective vector, the brown citrus aphid (BrCa) (Toxoptera citricida Kirk.), have been present together in Hawaii for over 50 years. In this study the incidence, diversity, and population structure of Hawaiian CTV strains was examined. Samples collected on Kauai (8 sites, 91 trees), Oahu (13, 86), Molokai (4, 12), Maui (10, 87), and Hawaii (15, 129), underwent RT-PCR for the CTV coat protein gene as well as tissue blot immunoassays (TBIAs) using five CTV antibodies. Samples testing positive for either RT-PCR or TBIA underwent further RT-PCR using primers specific to CTV genotypes T3, T30, T36, and VT. The incidence of CTV on Kauai, Oahu, Molokai, Maui, and Hawaii was 59, 87, 58, 63, and 83%, respectively, with an overall incidence of 74% (298/405). Strains with similarity to T3, T30, T36, and VT genotypes were identified in these samples, although their distribution was not uniform throughout the islands. Most infections, however, were composed of CTV strains that did not resemble any of these genotypes. The coat protein (CP) sequence was determined for over 100 Hawaiian CTV strains. Phylogenetic analysis using sequences as well as CP sequences of CTV strains from other parts of the world indicate that Hawaii has previously uncharacterized strains of the virus.