<scp>PM</scp> 7/31 (2) Citrus tristeza virus

EPPO BulletinVolume 53, Issue 1 p. 42-61 STANDARD ON DIAGNOSTICSFree Access PM 7/31 (2) Citrus tristeza virus First published: 05 February 2023 https://doi.org/10.1111/epp.12908AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text full-text accessPlease review our Terms and Conditions of Use check box below share version article.I have read accept the Wiley Online Library UseShareable LinkUse link a this article with your friends colleagues. Learn more.Copy URL Specific scope: This Standard describes diagnostic protocol for citrus virus.1 should be used in conjunction 7/76 protocols. approval amendment: approved 2003–09. revision 2022–11. was initially prepared align Diagnostic Protocol IPPC adopted 2016 (Annex 15 ISPM 27. (FAO, 2016)). However, it also includes other tests evaluated framework EU funded project VALITEST. INTRODUCTION (CTV) causes one most damaging diseases citrus, devastating epidemics οf which changed course industry (Moreno et al., 2008). The term ‘tristeza’, refers decline seen many species when grafted on aurantium (sour orange) or limon (lemon) rootstocks. Although is predominantly bud union disease (Román 2004), some CTV isolates induce syndromes, including stem pitting, stunting, reduced productivity impaired fruit quality commercial cultivars, even they are tolerant probably originated from South-East Asia, putative area origin has been disseminated almost all citrus-growing countries through movement infected plant material. Subsequent local spread by aphid vector created major epidemics. Tree losses sour orange rootstock were first reported South Africa early twentieth century, Argentina Brazil 1930s. CTV-induced tree killed rendered unproductive trees (Bar-Joseph 1989; Cambra 2000). outbreaks observed United States, Caribbean Mediterranean (especially Italy Morocco). Detailed information distribution can found Global Database (EPPO, 2021a). Like viruses, quasi-species, implies that plants contain population different genotypes. In case CTV, these genotypes belong phylogenetic groups, hampers establishment an unambiguous relationship between genotype pathogenic characteristics (Harper, 2013). Moreover, establishing such relation further complicated recombination. It noted ‘strain’ literature both as synonym ‘isolate’ group their molecular and/or biological properties (EFSA, 2017). Therefore, Panel Diagnostics Virology Phytoplasmology decided use concept genetic strain characteristics. To date, six groups described: T36 (Karasev 1995), T3 (Hilf unpublished), VT (Mawassi 1996), T30 (Albiach-Marti 2000), RB (Harper 2010) T68 2013) based genomic features. region, three either absent (T68) limited (RB & T36) (Cevik 2013; Ghosh 2022). present region represent only fraction diversity throughout world. Consequently, introduction belonging ‘foreign’ will increase may affect impact virus. important able identify at phylogenetic-group level order prevent within region. sequence variants genetically similar those pitting-inducing non-European detected Europe (i.e. VT, T3) involved severe symptoms, pitting symptoms sweet not surveys. Biological indexing resulted rare occurrence inconspicuous indicator plants. Outside Europe, main producing world, causing appear naturally transmitted semi-persistent manner. Worldwide, efficient Toxoptera citricida (Kirkaldy). Aphis gossypii Glover Spain, Israel, growing areas California (United States) where T. (Cambra 2000; Marroquín 2004; Yokomi 1989). Other described vectors 2008), spiraecola Patch, aurantii (Boyer de Fonsicolombe), Myzus persicae (Sulzer), craccivora Koch Uroleucon jaceae (Linnaeus). Information available datasheet graft-transmitted, but seed. Under natural conditions, readily infects Fortunella genera known citrus-relatives family Rutaceae. A list host Routine testing focusses material covered Standard. flow diagram describing procedure presented Figure 1. FIGURE 1Open figure viewerPowerPoint Flow samples. 2 IDENTITY Preferred name: names: closterovirus Acronym: Taxonomic position: Viruses, Riboviria, Closteroviridae, Closterovirus code: CTV000 Phytosanitary categorization: A2 n°93, A1 Quarantine pest II) non isolates, PZ III) RNQP IV) Note phytosanitary non-EU cause range crops do induce. For reason, Union quarantine pests Throughout document, referred ‘severe isolates’. Virus nomenclature protocols latest release official classification International Committee Taxonomy Viruses (ICTV, Release 2021, https://talk.ictvonline.org/taxonomy/). Accepted names italicized taxonomic context, whereas not, corresponding ICTV instructions. integration genus name currently consistently working and, therefore include name. Names viruses included reports. Transfer binomial progress (ICTV website) implemented gradually Protocols. 3 DETECTION Symptoms symptom expression CTV-infected hosts highly variable influenced environmental isolate. general, reticulata (mandarin) show symptoms. sinensis (sweet orange), C. orange, seedling rootstock), jambhiri (rough lemon) limonia (mandarin lime) usually symptomless, isolates. develop aurantiifolia (lime), macrophylla (alemow), paradisi (grapefruit cultivars pomelo), hybrids relatives Depending isolate rootstock/scion combination, no tristeza, yellows (Dawson Moreno Garnsey, 2010). Typically, mild produce noticeable species, remain symptomless years. Types pathogenicity associated Table TABLE groups. Phylogenetic Type field SY, QD, SP NNa SP, QD SD Pathogenicity Mild Severe Abbreviations: NN, generally symptoms; quick decline; SD, slow pitting; yellows. island Crete inducing orange. note ‘Candidatus Liberibacter’ spp. (huanglongbing) present, co-infection pathogens common lead increased severity due synergism (Fu same stands [e.g. Phytophthora spp., psorosis (CPsV) Argentina, sudden death (CSDaV) Brazil, exocortis viroid (CEVd) sensitive rootstocks] conditions. basin particular, drought greatly contributing syndrome (M. Cambra, pers. comm.). 3.1.1 Tristeza (decline syndrome) develops susceptible rootstocks-scion combinations. vast majority sinensis, reticulata, paradisi, rootstocks limon. extremely rapid (‘quick decline’), wilting occurring few days weeks, slower process (‘slow appearing over months years 2014). Decline resemble caused root injury. These thinning foliage, twig defoliation dieback, delayed growth possibly collapse. Trees slowly bulge above union, brown line just point inverse pinhole (honeycombing) inner face bark. On hosts, leaf cupping, vein clearing, chlorotic leaves, size commonly observed. 3.1.2 Stem (caused T3, occasionally groups) occurs regardless varieties seriously trees, trunk branches lime, grapefruit results vigour. inoculated seedlings sometimes bumpy ropy appearance trunks limbs adult deep pits wood under depressed bark, reduction yield. 3.1.3 Seedling T36, young lemon, notably greenhouse conditions (20–26°C) rather than situations. characterized production pale development system, stops aurantium, seedlings. Figures 2-12 CTV. 2Open Decline: Leaf chlorosis (a, b) (b top) rootstock. (a) healthy left. (b) right. Courtesy: Varveri C, BPI, Greece. 3Open Bud-union rootstock, pin holing honeycombing bark tree. Navarro L P, IVIA, Spain. 4Open Seedlings Duncan syndrome. Healthy R, ARS-USDA Parlier, USA. 5Open 6Open grapefruit. Harper SJ, Washington State University, US. 7Open Mexican lime. 8Open 9Open induced small fruits (compared normal hand) Uruguay. M, ES. 10Open cupping Courtesy University (US). 11Open Vein clearing SJ (US) 12Open alemow. P (formerly ES) Test sample requirements General guidance sampling methodologies 31Methodologies consignments2 al. (2002) specifically sampling. Procedures preparation Appendix 3.2.1 Plant Collection hand recommended avoid mechanical contamination (e.g. using scissors). Samples (shoots fully expanded leaves peduncles) taken year round grapefruit, mandarin temperate climates. Spring autumn optimal periods because highest titres during seasons. During summer, temperatures rise 35°C. decision test samples (e.g., shoots, petioles) individual multiple serological methods depends expected concentration plants, prevalence (Vidal 2012), confidence required NPPO. examples given below. consist shoots. Fruits flowers tested. stored 4°C up 7 before processing. month 4°C. −20°C −80°C longer periods. 3.2.1.1 Leaves best tissue petiole. orchards, standard consists ten collected canopy scaffold branches. 5 pooled tests. Greece, 4 ELISA 25 (Sambade 2002). nursery composed four per plant. Experience shows pooling five 3.2.1.2 Shoots shoots two 10 detection. From woody phloem scrapings taken. 3.2.1.3 peduncles Tissue peduncle (taken junction fruit), columella (Figure 13) testing. 13Open Columella (courtesy Petter F, EPPO) 3.2.1.4 Flowers Screening 3.3.1 Serological Polyclonal monoclonal antibodies double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), double antibody indirect (DASI) triple-antibody (TAS-ELISA) direct print ELISA. kit Immunostrip Flashkit Agdia. Instructions how perform 7/125 2015) provided 2. 3.3.2 Molecular RNA extraction 3. following VALITEST (https://www.valitest.eu/) detect CTV: Conventional reverse transcription PCR (RT-PCR) (Olmos 1999), see 4. Real-time RT-PCR (Saponari Ipadlab, Bertolini (2008), 6. RT-LAMP (Wang 2013), 7. ‘Immunocapture (IC)-RT-PCR’ ‘IC-nested single closed tube’ used. An silico analysis (19 isolates) showed Saponari (2008) Wang (2013) groups/isolates included, unlike Olmos (1999) missed (GenBank acc. MF595989) (Varveri, real-time developed Ipadlab prints 2019) (see respective appendices). 3.3.3 8) certification programmes post entry trees. considered reliable method detection characterization new unusual disadvantages: time consuming (symptom requires 6 post-inoculation); dedicated containment facilities temperature-controlled insect-proof greenhouses; experienced staff who accurately interpret confused graft-transmissible agents. addition, (latent detectable “strain K” Albertini (1988) data available). always combination another test. IDENTIFICATION Identification Section 3.3 allow identification findings containing (potentially) (stem pitting) orchards break resistance. Assignment strains3 assignment (genotypes) strains Sections 4.2.1 4.2.2, respectively. provides overview (assessed indexing) Since alone value prediction 2010; 2010), needed conclusive Available characterize T36a T68a RBa,1 T3b VTb T30b Method/Test (Appendix (assignment strains) Potentially types All yellowing, HTS ✓ Multiplex conventional (Roy ✓2 (Yokomi ✓3 ✓4 – (Cook 2016)5 Two-step One-step yellows; ✓, (or tests) suitable assign groups; –, does group. Able overcome trifoliata cannot distinguished. T68, Results obtained probes combined Two specific RT publication. Note: b additional relate presence not. Not countries. Present particular Validation available. Their analytical specificity (inclusivity-exclusivity) needs representative include: simplex multiplex followed sequencing amplicon. Simplex primers (and probes) High-Throughput Sequencing (HTS) sequences obtained. Sanger amplicons (Bester 2021) allows (Ruiz-García 2019). Obtaining ‘near’ complete genome preferable. Sequence follow guidelines Appendices 8 7/129 DNA barcoding tool number regulated 2021b). 4.2.2 performed samples, assess features Further 8. REFERENCE MATERIAL controls, CTV-specific oligonucleotide primer non-profit institutions Instituto Valenciano Investigaciones Agrarias (IVIA), Centro Protección Vegetal y Biotecnología, Carretera Moncada-Náquera km 5, 46113 Moncada, Valencia, ([email protected]) DSMZ Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH Inhoffenstraβe B 38124 Braunschweig (DE). REPORTING AND DOCUMENTATION Guidelines reporting documentation 7/77 Documentation diagnosis. PERFORMANCE CHARACTERISTICS When performance available, description Expertise (http://dc.eppo.int), consult database there more detailed specificity, validation reports, etc.). FURTHER INFORMATION organism from: Moncada (Valencia). E-mail: [email protected]. Council Agronomic Research bioeconomy Centre Protection Certification, Via G. Bertero 22–00156 Rome. Italy. 9 FEEDBACK THIS DIAGNOSTIC If you any feedback concerning Protocol, if provide wish please contact REVISION annual place need Protocols identified needing marked website. errata corrigenda press, ACKNOWLEDGEMENTS originally drafted by: Gorris MT, Valencian Institute Agricultural (IVIA, Spain). Benaki Phytopathological (BPI, Greece), Faggioli F Ferretti L, Economics, Certification (CREA, Italy) A, reviewed Phytoplasmology. APPENDIX 1: SAMPLE PREPARATION Preparation freshly cut sections petioles, flower ovaries carefully pressed against nitrocellulose cellulose-ester membrane (0.45 mm) allowed dry 2–5 min. routine testing, least made selected shoot (one each end shoot) petiole ovary. Printed membranes kept several dark place. extracts 0.2–0.5 g fresh (leaf midribs, petioles scrapings) into pieces disposable razor blades bleach-treated scissors placed tube plastic bag. homogenized thoroughly 2–10 mL (from 1:10 1:20 w/v) buffer (PBS DIECA below) electrical homogenizer, manual roller, hammer tool. material, 0.2 (pooled consisting equal amounts tree), above, bags 1–20 1:1