Survey for ‘Candidatus Liberibacter’ and ‘Candidatus Phytoplasma’ in Citrus in Chile

The considerable economic losses in citrus associated with ‘Candidatus Liberibacter’ and ‘Candidatus Phytoplasma’ presence have alerted all producing regions of the world. In Chile, none of these bacteria have been reported in citrus species. During the years 2017 and 2019, 258 samples presenting symptoms similar to those associated with the presence of these bacteria were examined. No detection of ‘Ca. Liberibacter’ associated with “huanglongbing” disease was obtained in the tested samples; therefore, this quarantine pest is maintained as absent in Chile. However, 14 plants resulted positive for phytoplasmas enclosed in subgroups 16SrV-A (12 plants) and 16SrXIII-F (2 plants). Although they have been found in other plant species, this is the first report of these phytoplasmas in citrus worldwide.

Complete genome and plasmid sequence data of three Xanthomonas arboricola pv. corylina strains, the bacterium responsible for bacterial blight of hazelnut

Xanthomonas arboricola pv. corylina is the causal agent of bacterial blight of hazelnut. The bacterium is listed as A2 quarantine pathogen in Europe since 1978 and on the Regulated Non-Quarantine Pest (RNQP) list since 2020. Three strains from various geographic regions and isolated at different times were sequenced using a hybrid approach with short- and long-read technologies to generate closed genome and plasmid sequences in order to better understand the biology of this pathogen.

Citrus leprosis virus C (leprosis of citrus).

CiLV-C is a quarantine pest which causes an economically important disease, reported only on the American continent. During the past 15 years, it has caused economic losses in Brazil, Argentina, Paraguay, Uruguay, Venezuela, Costa Rica, Panamá and Honduras. The disease was recently reported in Guatemala, Bolivia, México, Colombia and Belize. It is a threat to citrus-producing countries where the disease has not been reported. The disease can cause 100% yield loss (Rodrigues et al., 2000).

Clover yellow mosaic virus.

Clover yellow mosaic virus is not recommended for regulation as a quarantine pest by EPPO and is not included in the EPPO Alert List. A comprehensive pest risk analysis was performed by the UK Food and Environment Agency (FERA): https://secure.fera.defra.gov.uk/phiw/riskRegister/downloadExternalPra.cfm?id=3804.

Aculops fuchsiae (Fuchsia gall mite).

A. fuchsiae, the fuchsia gall mite, is native to South America. It was first found in California, USA in 1981 where it has spread rapidly, and more recently it has invaded Europe since 2003, and it is a declared quarantine pest in both. It attacks only fuchsia (Fuchsia spp.), but once established it is very difficult to eradicate and impacts can be so severe that some growers in California have given up growing the plants entirely.

Pear blister canker viroid.

Pear blister canker disease, first reported in France in the 1960's, is caused by pear blister canker viroid (PBCVd). Diseases can occur in several cultivars of pear (Pyrus communis), its major host, but most pear cultivars are tolerant and do not produce symptoms of infection. PBCVd was initially reported in pear and quince, followed by wild pear and nashi and can experimentally infect species in other genera (Chaenomeles, Cydonia, Sorbus, Malus). Transmission through mechanical inoculation from pruning tools and grafting to infective propagative materials is a potential pathway for spread; no animal vector is known and it is not known to be seed transmitted. PBCVd has been reported in several European countries, Malta, Tunisia, Turkey, Australia, Japan, China, and the Americas; the geographic distribution may be underestimated because of symptomless infections in certain hosts. PBCVd was placed on the A1 list in Canada in 1995, listed as a quarantine pest in the United States in 1989, is regarded as quarantine pathogen for Australia, and is listed in a certification scheme to produce clean Pyrus and Cydonia sp. planting material in an OEPP/EPPO Bulletin in 1999 (OEPP/EPPO, 1999).

Candidatus Phytoplasma australiense.

Phytoplasmas are wall-less, phloem-limited unculturable bacteria that are naturally spread by sap-sucking insects. 'Candidatus Phytoplasma australiense', subgroup 16SrXII-B, is associated with a wide range of diseases in Australia and New Zealand. Important commercial crop hosts of 'Ca. Phytoplasma australiense' include grapevine, papaya and strawberry. This phytoplasma is associated with rapid death of its papaya and cabbage tree hosts. In New Zealand, the insect vectors have been confirmed to be the endemic Cixiid planthoppers, Zeoliarus atkinsoni and Z. oppositus, while in Australia no vector has yet been determined, although the leafhopper, Orosius argentatus, has been implicated. Long distance spread of the phytoplasma is possible through infected vegetative propagating material. 'Ca. Phytoplasma australiense' is on the A1 list of regulated organisms for Canada and Bahrain, and is listed as a quarantine pest for the USA.

Anastrepha suspensa (Caribbean fruit fly).

A. suspensa is a pest of guava [Psidium guajava], grapefruit [Citrus x paradisi], and various other cultivated fruits. It is native to the Greater Antilles and possibly the Bahamas, and is an introduced pest in Florida, USA. It is considered an A1 quarantine pest by EPPO.

Clover yellow mosaic virus.

Clover yellow mosaic virus is not recommended for regulation as a quarantine pest by EPPO and is not included in the EPPO Alert List. A comprehensive pest risk analysis was performed by the UK Food and Environment Agency (FERA): https://secure.fera.defra.gov.uk/phiw/riskRegister/downloadExternalPra.cfm?id=3804.