Maria Laura Garcia

The complete nucleotide sequence of a Spanish isolate of Citrus psorosis virus: comparative analysis with other ophioviruses.

Summary.The complete genomic sequence (11278 nt) of Citrus psorosis virus (CPsV), isolate P-121 from Spain, was determined and compared with those from isolate CPV-4 and from other ophioviruses. The three RNAs of P-121 had similar size and identical organization as those of CPV-4. The 24K and the RdRp proteins were potentially encoded in the viral complementary (vc) strand of RNA 1, the 54K protein potentially encoded in vcRNA 2 and the coat protein encoded in vcRNA 3. These four proteins from P-121 and CPV-4 had 87, 92, 93 and 94% amino acid identity, respectively, but only 22, 38, 25 and 33% identity with their homologous proteins from Mirafiori lettuce big vein virus (MLBVV), the only other ophiovirus completely sequenced. Biological and genetic differences between CPsV and MLBVV (and the other ophioviruses), would support their future allocation in different genera within a tentative family Ophioviridae.

A highly sensitive heminested RT-PCR assay for the detection of citrus psorosis virus targeted to a conserved region of the genome.

Psorosis is a widespread and damaging disease of citrus in many parts of the world. The causal agent is a multipartite virus with RNA genome present in very low concentration in infected citrus tissue. Diagnosis is made by biological indexing on indicator citrus seedlings, but it is a slow and costly procedure and therefore it is not used generally. No sensitive wide-spectrum assay for Citrus Psorosis virus (CPsV) has been reported based on RT-PCR. A highly sensitive heminested RT-PCR assay is described for the detection of CPsV. Fragments of 313 bp amplified from RNA 1 of different isolates were cloned and sequenced. Very high homology was found among six isolates from the citrus producing region of Argentina: 96.6-100% in nucleotide sequence. The consensus sequence obtained was used for the design of the primers for heminested PCR assay. It has been tested on different Argentine isolates, employing various methods for RNA extraction from infected tissue. This test is able to detect CPsV in dilutions of 10(10) of the original sample.

Transgenic sweet orange plants expressing a dermaseptin coding sequence show reduced symptoms of citrus canker disease.

Citrus canker provoked by Xanthomonas axonopodis pv. citri is a bacterial disease causing severe losses in all citrus-producing areas around the world. Xanthomonas infection is considered as an endemic disease in Northeast and Northwest Argentina, affecting as much as 10% of commercial citrus plantations. There is not known natural resistance neither in orange varieties nor in rootstocks used for grafting of commercial cultivars. To introduce resistance to this disease, plants of Pineapple sweet orange were transformed with a genetic construct allowing constitutive accumulation of dermaseptin. In comparison with non-transformed plants, transgenic plants showed symptom reduction levels of up to 50% in in planta assays performed under controlled conditions.

A fast one-step reverse transcription and polymerase chain reaction (RT-PCR) amplification procedure providing highly specific complementary DNA from plant virus RNA.

Reverse transcription and polymerase chain reaction (RT-PCR) are being used increasingly for detection and typing RNA viruses. For this purpose, metal block thermal cyclers (MBTC) are considered to provide higher DNA yield, whereas air thermal cyclers (ATC) allow PCR amplification in a much shorter time. A fast ATC protocol (0 s denaturation, 0 s annealing, and 4-8 s elongation) was developed to amplify genomic segments from two RNA viruses, which allowed increasing the number of cycles without a parallel increase of non-specific DNA fragments. Under these conditions, 80-90 cycles with the ATC provided a DNA yield close to that of a standard 40-cycles MBTC protocol in about half the time. The DNA synthesised by the new procedure was highly specific and could be cloned readily.

Current status of prenatal diagnosis in Cuba: causes of low prevalence of Down syndrome

To analyze trends in cytogenetic prenatal diagnosis in Cuba and to analyze possible causes leading to a low Down syndrome prevalence in a country where the triple test is not available.

Corrigendum: ICTV Virus Taxonomy Profile: Ophioviridae

The International Committee on Taxonomy of Viruses has ratified a taxonomic proposal to change the name of the family Ophioviridae to Aspiviridae, and to change the names of species in the family to Blueberry mosaic associated ophiovirus, Citrus psorosis ophiovirus, Freesia sneak ophiovirus, Lettuce ring necrosis ophiovirus, Mirafiori lettuce big-vein ophiovirus, Ranunculus white mottle ophiovirus and Tulip mild mottle mosaic ophiovirus. These species are all members of the genus Ophiovirus, the genus name being unchanged.

Ascosphaera apis, the entomopathogenic fungus affecting larvae of native bees (Xylocopa augusti): First report in South America.

BACKGROUND Nowadays several invertebrate pollinators of crops and wild plants are in decline as result of multiple and, sometimes, unknown factors; among them, the modern agricultural practices, pests and diseases are postulated as the most important factors. Bees of the genus Xylocopa are considered effective pollinators of passion fruit crops in tropical regions, as well as important pollinators in wild plants, but these bees are attacked by several pathogens that affect different stages in their life cycle. The fungal species of the genus Ascosphaera are commonly associated with social and solitary bee larvae causing chalkbrood disease. AIMS The aim of the present study was to demonstrate the presence of Ascosphaera apis affecting larvae of Xylocopa augusti in South America. METHODS For this purpose, A. apis was isolated from affected larvae in YGPSA medium. Final identification was run out by three techniques: (1) Microscopic examination of the hyphae and sizes of the fruiting bodies; (2) Mating test, and specific sexual compatibility test, and (3) PCR detection, using specific primers. RESULTS This study demonstrates for the first time the presence of A. apis affecting larvae of X. augusti in South America. CONCLUSIONS The evidence of A. apis affecting the larvae of X. augusti, and the fact that the sharing of pathogens between different bee species has been underestimated, suggests the need for further epidemiological studies in order to determine not only the prevalence of this pathogen among wild pollinators, but also its relationship to the sudden collapse of honey bee colonies in this region.

An update of Africanization in honey bee (Apis mellifera) populations in Buenos Aires, Argentina

European and African honey bee populations have been separated and influenced by different environments. Furthermore, Apis mellifera is the only species of honey bees that evolved in Europe, the Middle East, and Africa, where several subspecies are recognized. A. m. scutellata was introduced in Brazil in 1956, resulting in the spread of African bees throughout South and Central America. The aim of the present study was to determine the prevalence and geographical distribution of Africanized bees in Buenos Aires province (Argentina) employing a mtDNA cytochrome b polymorphism. A total of 430 colonies were sampled between 2013 and 2014; eighteen out of them (4,2%) belonged to African linage. Our results confirm that European haplotypes are the most prevalent in Buenos Aires Province, and that the process of African gene introgression remains stable since 2005.

ICTV Virus Taxonomy Profile: Ophioviridae

The Ophioviridae is a family of filamentous plant viruses, with single-stranded negative, and possibly ambisense, RNA genomes of 11.3–12.5 kb divided into 3–4 segments, each encapsidated separately. Virions are naked filamentous nucleocapsids, forming kinked circles of at least two different contour lengths. The sole genus, Ophiovirus, includes seven species. Four ophioviruses are soil-transmitted and their natural hosts include trees, shrubs, vegetables and bulbous or corm-forming ornamentals, both monocots and dicots. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Ophioviridae, which is available at http://www.ictv.global/report/ophioviridae.