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This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2020-0114), at the request of the European Commission. Its purpose is to guide the Member States in preparing data and information for surveys of citrus leprosis viruses. These are required to design statistically sound and risk-based pest surveys, in line with current international standards. Six of the seven viruses that cause citrus leprosis (CiLV-C, CiLV-C2, HGSV-2, OFV, CiLV-N sensu novo and CiCSV) are clearly defined taxonomic entities, while the status of CiBSV is unclear. CiLV-C, CiLV-C2, HGSV-2, the citrus strain of OFV, CiLV-N sensu novo and CiCSV are Union quarantine pests. Citrus leprosis viruses do not cause systemic infections and they are all exclusively transmitted by mites of the genus Brevipalpus. Brevipalpus mites associated with the transmission of the leprosis disease are present in some regions of EU territory. The commercial citrus species most relevant to the EU are considered susceptible to citrus leprosis disease. There are no ecoclimatic constrains known for the citrus leprosis viruses, except for those affecting their host plants and their mite vectors. Therefore, due to the wide availability of host species and the presence of Brevipalpus mites, all citrus-growing areas in the EU are considered potentially suitable for the viruses to become established. Long-distance spread is likely to occur through movement of viruliferous mites phoretically associated with commodities. Detection of citrus leprosis viruses in the field should be performed by visual examination of symptoms followed by sampling and molecular identification in the laboratory. Visual examination should be preferably conducted in late summer / early autumn. Based on the analyses of the information on the pest-host plant system, the various units that are needed to design a survey should be defined and tailored to the situation in each Member State.

En los cítricos la autoincompatibilidad (AI) es un carácter de gran interés ya que en cultivares partenocárpicos permite la obtención de frutos sin semillas. Sin embargo, la AI supone un obstáculo para la realización de estudios genéticos y para los programas de mejora genética basados en hibridación sexual. El estrés por temperatura, la polinización de flores en estado prematuro del desarrollo (botones florales) y la poliploidización son factores que pueden inducir la ruptura de la AI. En este trabajo se ha evaluado esta ruptura en dos cultivares diploides autoincompatibles: clementina ‘Clemenules’ (C. clementina Hort. ex Tan.) y mandarino ‘Fortune’ (C. clementina x C. tangerina).

Actualmente, la citricultura española no tiene grandes problemas de enfermedades gracias al Programa de Mejora Sanitaria de Variedades de Cítricos que se estableció en 1975 y que ha permitido la renovación total de las plantaciones con material sano. Sin embargo, las perspectivas sanitarias en el futuro son preocupantes debido a graves enfermedades como Huanglongbing, clorosis variegada y cancrosis, que están presentes en otros países y que suponen una seria amenaza para nuestra citricultura.

Citrus psorosis virus (CPsV), genus Ophiovirus, causes an important disease in many countries. In growing regions where natural disease spread occurs, damage caused by the virus can be controlled using resistant or tolerant cultivars, but sensitivity of many species and hybrids of Citrus and related genera is presently unknown. To find potential sources of CPsV resistance, we first propagated 61 species (or cultivars) and hybrids of Citrus and related genera [Citrus (37), Microcitrus (5), Fortunella (6), Eremocitrus (1), Pleiospermium (1), Atalantia (1), Severinia (1), Clausena (1), Poncirus (1) and hybrids (7)] on Rough lemon seedlings inoculated with the CPsV isolate PB 143. Out of the 61 accessions tested 54 showed symptoms and reacted by ELISA with a CPsV-specific antibody, 2 (M. inodora and F. hindsii) were symptomless but gave high ELISA values, suggesting tolerance to CPsV, 5 (C. depresa, Cleopatra mandarin, C. excavata, Carrizo citrange and CPB 4475 citrumelo) showed symptoms in the first flush but gave a negative ELISA reaction, and 1 (Poncirus trifoliata) was ELISA negative and symptomless. We then examined CPsV infection by ELISA and RT-PCR in Cleopatra mandarin, P. trifoliata and Citrumelo seedlings inoculated with CPsV isolates P 121, PB 108 and PB 143. While P 121 was detected in all Cleopatra and citrumelo plants, the other isolates were detected in only 50% of the inoculated plants, with all plants indexed as CPsV positive displaying symptoms. All P. trifoliata plants inoculated with either isolate indexed negative for CPsV and remained symptomless. Our results suggest CPsV resistance in P. trifoliata and partial isolate-specific resistance in some accessions.

Psorosis disease of citrus is characterized by bark scaling in the stem and main branches of trees at least 10 years old. Graft-inoculation of sweet orange (Citrus sinensis (L.) Osb.) seedlings in the greenhouse with non-scaled bark pieces from an infected tree incites the psorosis A syndrome (PsA), including a shock reaction of the first flush and transient chlorotic flecking in young leaves of the following flushes, whereas inoculation with scaled bark pieces incites the psorosis B syndrome (PsB), that in addition to PsA symptoms includes gummy pustules in old leaves and branches. Psorosis disease is presumably caused by Citrus psorosis virus (CPsV), an ophiovirus with three negative-stranded genomic RNAs. While comparison of RNA1 or RNA3 fragments by single-strand conformation polymorphism (SSCP) analysis did not show any difference between plants affected by the PsA or the PsB syndromes, a fragment of RNA2 enabled discriminating both syndromes by their SSCP profile. A plant inoculated with scaled bark did not show PsB at 6 months post-inoculation (mpi) and its RNA2 gave a PsA-type SSCP profile. At 12 mpi this plant showed pustules in the trunk but not in the leaves. SSCP analysis of RNA2 showed only PsA-type variants in the leaves, whereas the pustuled trunk areas contained both PsA and PsB variants, the latter being predominant. These results suggest that psorosis-affected trees contain the two sequence variants and that the PsB variant is associated with pustules and tends to accumulate in the trunk bark.

To invade systemically host plants, viruses need to replicate in the infected cells, spread to neighbouring cells through plasmodesmata and move to distal parts of the plant via sieve tubes to start new infection foci. To monitor the infection of Nicotiana benthamiana plants by Citrus leaf blotch virus (CLBV), leaves were agroinoculated with an infectious cDNA clone of the CLBV genomic RNA expressing green fluorescent protein (GFP) under the transcriptional control of a duplicate promoter of the coat protein subgenomic RNA. Fluorescent spots first appeared in agroinfiltrated leaves 11-12 days after infiltration, indicating CLBV replication. Then, after entering the phloem vascular system, CLBV was unloaded in the upper parts of the plant and invaded all tissues, including flower organs and meristems. GFP fluorescence was not visible in citrus plants infected with CLBV-GFP. Therefore, to detect CLBV in meristematic regions, Mexican lime (Citrus aurantifolia) plants were graft inoculated with CLBV, with Citrus tristeza virus (CTV), a virus readily eliminated by shoot-tip grafting in vitro, or with both simultaneously. Although CLBV was detected by hybridization and real-time reverse transcription-polymerase chain reaction (RT-PCR) in 0.2-mm shoot tips in all CLBV-inoculated plants, CTV was not detected. These results explain the difficulty in eliminating CLBV by shoot-tip grafting in vitro.

La citricultura española ha estado condicionada a lo largo de su historia por la presencia de enfermedades graves. A finales del siglo XIX se inició la primera expansión de las plantaciones comerciales. Las variedades se injertaban sobre los portainjertos naranjo dulce, limonero, cidro o naranjo amargo. En 1892, cuando existían unas 4.000 ha de cítricos, se observaron los primeros ataques del hongo Phytophthora sp., que en 10-15 años causó la muerte de todos los árboles existentes, excepto los que estaban injertados sobre el portainjertos naranjo amargo, que es tolerante al mismo. Además, este portainjertos tiene un excelente comportamiento agronómico, por lo que a partir de entonces seutilizó de forma exclusiva en todas las nuevas plantaciones. A principios del siglo XX ya existían unas 18.000 ha y una parte importante de la producción se exportaba a diversos países europeos. La rentabilidad y expectativas del cultivo hicieron que en periodo 1910-1930 se realizase la importación de variedades de diversos países que permitieron una importante renovación varietal y una producción más adaptada a la demanda. Sin embargo, estas importaciones se realizaron sin controles sanitarios, entre otras razones porque en esa época se desconocía la presencia en cítricos de enfermedades causadas por virus y otros patógenos transmisibles por injerto. En 1930 ya se describen los primeros síntomas de algunas virosis y en 1956 se observaron las primeras muertes de árboles causadas por el virus de la tristeza de los cítricos (CTV), que se transmite por pulgones y causa la muerte de naranjos y mandarinos injertados sobre naranjo amargo. La enfermedad se difundió rápidamente causando daños muy importantes en las plantaciones y a finales de la década de los años 60 la amenaza de un grave desastre socioeconómico se hizo muy evidente. En esa época la exportación de cítricos era la principal fuente de divisas para el país, lo que añadía una problemática adicional