Occurrence and distribution of citrus leprosis virus in Honduras

Citrus leprosis virus is characterised by bullet-shaped particles occurring in the nucleus (CiLV-N) or cytoplasm (CiLV-C) of infected plant cells. Ongoing molecular and cytopathological studies suggest that CiLV-N and CiLV-C are in fact two different viruses, with CiLV-C being the most commonly associated with the disease (Rodrigues et al. , 2003). Both viruses are vectored by Brevipalpus spp. mites (Acari; Tenupalpidae).

During a survey in Honduras in 2003, leprosis disease symptoms (Fig. 1 & 2) were observed in the municipality of Siguatepeque, near La Esperanza (N 14 37 12 / W 87 54 20). Symptoms were conspicuous, with old plants showing dieback and strong defoliation. On a scale of severity (Rodrigues, 2002), these plants reached the highest level; suggesting that the disease had arrived in the area several years earlier. Symptoms were also observed at a second site in the Department of Comayagua, about 45 km east of La Esperanza. At both sites, symptoms were observed in sweet orange ‘Valencia’ and ‘Navel’, butof leprosis virus in orange (Rodrigues et al. , 2003). All plants with symptoms were found in backyards. The disease was detected at a third site, Lago de Yojoa (N 14 47 51 / W 87 54 20) and was initially thought to have been eliminated. However, trees with leprosis symptoms were refound in the area and all citrus plants were subsequently eliminated from the site. Additional inspections were conducted by Pronavif personnel at 206 sites, located in the major citrus industry regions of El Progresso and La Ceiba, but no symptoms of the disease were found. Tissue from leaves with symptoms was fixed in 3% glutaraldehyde and ultra thin sections were analyzed using transmission electron microscopy (TEM) at two microscopy facilities (Univ. of Florida and São Paulo). Tenuipalpid mites were collected, fixed in 70% ethanol for identification by morphology, and in 90% ethanol for identification by molecular analysis (Rodrigues et al. , 2004). Care was taken to avoid carrying out any living material from the inspected sites.

Using TEM, particles typical of CiLV-C were observed in symptomatic samples from all positive sites (Fig. 3). CiLV-N was not detected in any of the samples. The tenuipalpid mites found in association with the infected sweet orange trees were morphologically identified as Brevipalpus phoenicis . This identification was confirmed by mitochondrial DNA analysis . Before 2001, this devastating citrus disease had not been reported outside of South America; it has since been detected in Central America (Dominguez et al. , 2001). While symptoms of leprosis disease have been previously reported (E. Ayers, personal communication), the causal agent had never been confirmed. This is the first confirmed report of CiLV-C in Honduras.