Search

In autumn 2001, severe yellowing symptoms were observed on greenhouse-grown cucumbers near Perpignan (southern France). Leaf samples were collected from two sites where plants displayed symptoms ranging from limited yellowing of the older leaves to severe, complete yellowing of the whole plant. Cucurbit aphid-borne yellows virus, a polerovirus that causes similar symptoms was not detected in doubleantibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using a specific antiserum. Total RNA was extracted from fresh leaf tissues and used in reverse transcription-polymerase chain reaction (1) with primers specific for two whitefly-borne viruses also inducing yellows and occurring in the Mediterranean basin (1): Beet pseudo yellows virus (BPYV, genus Closterovirus) transmitted by Trialeurodes vaporariorum (West.) and Cucurbit yellow stunting disorder virus (CYSDV, genus Crinivirus) transmitted by Bemisia tabaci (Genn.). No BPYV was detected in this survey, but CYSDV was present in all samples. In subsequent surveys conducted in the spring and summer of 2002, BPYV and CYSDV were detected, sometimes in mixed infections, in samples collected from the same region. The complete CYSDV coat protein gene was amplified by PCR using specific primers (2), yielding the expected-size fragment of 756 bp. The French isolate (GenBank Accession No. AY204220) shared 99.6 to 100% nucleotide sequence identity in the sequenced CP fragments (700 nt) with isolates of the most common, highly homogenous subgroup of CYSDV that has emerged recently in the Middle East, southwestern Europe (Spain and Portugal), United States, and Morocco (2). To our knowledge, this is the first report of CYSDV in France and it shows the threat represented by the current emergence of B. tabaci-transmitted viruses. References: (1) I. C. Livieratos et al. Plant Pathol. 47:362, 1998. (2) L. Rubio et al. J. Gen. Virol. 82:929, 2001.

International audience; Complete genomic sequences of Artichoke latent virus (ArLV) have been obtained by classical or high-throughput sequencing for an ArLV isolate from Italy (ITBr05) and for two isolates from France (FR37 and FR50). The genome is 8,278 to 8,291 nucleotides long and has a genomic organization comparable with that of Chinese yam necrotic mosaic virus (CYNMV), the only macluravirus fully sequenced to date. The cleavage sites of the viral polyprotein have been tentatively identified by comparison with CYNMV, confirming that macluraviruses are characterized by the absence of a P1 protein, a shorter and N-terminally truncated coat protein (CP). Sequence comparisons firmly place ArLV within the genus Macluravirus, and confirm previous results suggesting that Ranunculus latent virus (RALV), a previously described Macluravirus sp., is very closely related to ArLV. Serological relationships and comparisons of the CP gene and of the partial RaLV sequence available all indicate that RaLV should not be considered as a distinct species but as a strain of ArLV. The results obtained also suggest that the spectrum of currently used ArLV-specific molecular hybridization or polymerase chain reaction detection assays should be improved to cover all isolates and strains in the ArLV species.

INRA, CENTREX and CEP INNOVATION are developing new apricot cultivars for French growers with particular attention paid to consumer's expectations. The main objectives of the related breeding programme are: production regularity, fruit quality and attractiveness. Their evaluation is based on a multilocal and pluri-annual set of trials located in the three major French areas of cultivation and organised as a 3-stage-evaluation: (i) observation of the seedlings on their own roots (ii) evaluation of the best grafted selections in the 3 main areas, (iii) assessment of the agronomic and commercial interest of the 'elite' accessions in small commercial orchards. At the end of the selection process two recent main types of cultivars have been introduced: - Ten new cultivars able to enlarge the harvesting season by 'conventional' type of fruit ('Soledane', 'Solimar'@, 'Candide', 'Bergerval'@, 'Bergarouge'®, 'Royal Roussillon', 'Vertige', 'Fantasme'@, 'Helena du Roussillon'®, 'Frisson'); - Three new fruit-type apricots characterized by a stark red blush covering 80% of the fruit shape, developed under the same trademark, 'Rubisco'@ (Ravival, Ravilong and Ravicile).

National audience

International audience; Collaborative research was conducted at the INRA Research Centers to assess the microbial control potential of Beauveria bassiana- and Lecanicillium lecanii-based formulations against whiteflies in protected crops under Mediterranean conditions. Four series of small-scale glasshouse trials were performed in 1999 and 2000 in southern France. Two applications at 4-5 day intervals of Naturalis-L and Mycotal were conducted on young larvae of the greenhouse whitefly, Trialeurodes vaporariorum, at rate's recommended by the manufacturers. Because of the expectation that environmental conditions prevailing in Mediterranean greenhouse crops may lead to greater climatic constraints for mycoinsecticide efficacy than in more temperate areas, manipulation of the greenhouse climate has been used to aim at optimizing mycoinsecticide efficacy. The climatic management strategy was mainly based on closing the ridge vents 2 h more at night-time in so-called "humid" glasshouse compartment than in a "dry" one. Thus, the daily period at high humidity (>90% RH) was two or three times longer in the "humid" compartment than in the "dry" one. In spite of this differential, mycoinsecticide treatments reduced numbers of surviving whitefly larvae by >85% in the "humid" compartment as expected as favorable, as well as in the "dry" compartment, expected as unfavorable. The results indicated clearly that both B. bassiana- and L. lecanii-based mycoinsecticides have a strong potential for microbial control of whitefly larvae infesting tomato crops at moderate ambient humidity in Mediterranean glasshouses. Our investigations provided strong arguments for explaining these unexpected results. The RH conditions prevailing in the targeted insect habitat should be greatly disconnected from that of the ambient glasshouse air. We suggest that strategies of mycoinsecticide optimization against phyllophagous insects in protected crops have to take into account factors acting on the leaf transpiration activity. (C) 2003 Elsevier Science (USA). All rights reserved.

In June 2008, tomato (Solanum lycopersicum L.) plants cv. Fer De Lance (De Ruiter Seeds, Bergschenhoek, the Netherlands) grown in greenhouses near Perpignan (southern France) showed growth reduction and necrotic lesions on fruits, stems, and basal parts of the leaves. Tomato torrado virus (ToTV) was suspected on the basis of symptoms and its recent description in Spain (4). Primer set A (3), designed to ToTV RNA-2, was used for reverse transcription (RT)-PCR experiments on RNA extracted from four infected plants and allowed the amplification of a 493-bp fragment. No amplification was observed from healthy plant extracts. The RT-PCR product was directly sequenced (GQ303330) and a BLAST search in GenBank revealed 99.8- and 99.5%-nt identity with Polish (EU563947) and Spanish type strain (DQ388880) isolates of ToTV, respectively. Double-antibody sandwich-ELISA tests were conducted on these four samples to check for the presence of other viruses commonly found in tomato crops in France. Tomato spotted wilt virus, Parietaria mottle virus, Cucumber mosaic virus, Tomato mosaic virus, and Potato virus Y were not detected but Pepino mosaic virus (PepMV) was detected in all samples. ToTV was mechanically transmitted to Physalis floridana but PepMV was not. This plant was used to inoculate healthy tomatoes that served as a ToTV source for further experiments. Mechanical inoculation to test plants showed that Nicotiana benthamiana, N. clevelandii, N. debneyi, N. glutinosa, Capsicum annuum, Solanum melongena, and some tomato cultivars (including Fer De Lance), in which typical necrotic symptoms were observed, were systemically infected by the virus. Isometric particles ~28 nm in diameter were observed by electron microscopy in crude extracts of infected plants negatively stained with 1% ammonium molybdate, pH 7. To confirm ToTV identification, whitefly transmission experiments were performed with Trialeurodes vaporariorum and Bemisia tabaci. Adult whiteflies were placed in cages with infected tomato plants for 1-, 24-, or 48-h acquisition access periods (AAP) before transferring them by groups of ~50 on susceptible tomato plantlets placed under small containers (six plants per AAP). Forty-eight hours later, plants were treated with an insecticide and transferred to an insect-proof containment growth room. Ten days later, RNA preparation from all plants was tested by RT-PCR for the presence of ToTV. No transmission was observed with a 1-h AAP. With a 24-h AAP, transmission to four of six test plants was observed with both whitefly species, while at 48 h, AAP transmission to three and four plants of six was observed with T. vaporariorum and B. tabaci, respectively. Noninoculated control plants were all negative by RT-PCR. These experiments confirm T. vaporariorum and B. tabaci as natural vectors of ToTV as previously described (1,2). ToTV has been already reported in Spain, Poland, Hungary, and Australia, but to our knowledge, this is the first report of ToTV in France. Our detection of ToTV in April 2009 from the same area revealed 7 positive tomato plants of 17 tested. This observation suggests the persistence of the disease in the Perpignan Region. References: (1) K. Amari et al. Plant Dis. 92:1139, 2008. (2) H. Pospieszny et al. Plant Dis. 91:1364, 2007 (3) J. Van der Heuvel et al. Plant Virus Designated Tomato Torrado Virus. Online publication. World Intellectual Property Organization WO/2006/085749, 2006. (4) M. Verbeek et al. Arch. Virol. 152:881, 2007.

A 927 bp non-ribosomal fragment was used to assess the genetic variability of the European stone fruit yellows (ESFY) phytoplasma infecting 14 different Prunus species. For this, 175 isolates originating from four different Mediterranean countries were tested by PCR-RFLP analysis with seven restriction enzymes. No polymorphism among the ESFY phytoplasma could be observed but 12 out of 18 restriction sites differed between the homologous fragments of ESFY and apple proliferation (AP) phytoplasmas. An 846 bp fragment of a French ESFY isolate was sequenced, it included the 3'-end of a putative nitroreductase gene, an intergenic region and a truncated open reading frame. This ESFY phytoplasma sequence showed 89.7% identity with the equivalent AP phytoplasma nucleotide sequence (83. 9% identity at the amino acid level). The G+C content of the entire sequence was extremely low (15.4%) and A+T-rich codons were highly preferred in codon usage. In this paper, we report the presence of the ESFY phytoplasma for the first time in Turkey and in five Prunus hosts never reported previously. Our results also indicate that the ESFY phytoplasma isolates affecting various Prunus species are genetically homogenous but can be distinguished from the AP phytoplasma. Therefore, they are likely to represent different taxons.