Since 2002, yellowing symptoms associated with high levels of white-fly populations have been observed in plants of protected tomato crops in France. Symptomatic plants exhibited interveinal yellowing areas in older leaves, followed by generalized yellowing. Symptoms were not observed in young plants or fruits. Trialeurodes vaporariorum populations were generally abundant in spring, and Bemisia tabaci (established in France for approximately 10 years) became predominant in summer and fall. To check for the presence of Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV), two whitefly-transmitted criniviruses known to induce yellowing symptoms, 696 samples were collected in the major tomato-growing areas; 573 samples from southern France and 123 samples from northern France. Total RNA was extracted from each sample and analyzed using reverse transcription-polymerase chain reaction (RT-PCR). Primers specific to ToCV (2) and TICV (1,3) were used to amplify either part of the heat-shock-like protein gene HSP70h (both viruses) or part of the diverged coat protein gene (CPd), (TICV only). A 439-bp DNA fragment was obtained with ToCV primers in 178 samples from southern France collected mainly from mid-spring to early fall from 2002 to 2004. Three RT-PCR products amplified from samples collected from diverse growing areas were sequenced and showed 99 to 100% sequence identity with published ToCV sequences from Spain (GenBank Accession Nos. AF215818, AF233435, and AF215817), Portugal (GenBank Accession No. AF234029), Sicily (GenBank Accession No. AY048854), and the United States (GenBank Accession No. AF024630). Considering the high frequency of ToCV-infected samples (41 positive samples of 112 samples collected in 2002, 71 of 295 collected in 2003, and 66 of 166 collected in 2004), this virus appears to be well established in southern France but remains absent in the northern regions. The presence of TICV was tested in 485 samples using the CPd-specific primers or the HSP70h-specific primers. The virus was detected in only two samples from Nice (southeastern France) in 2003 with both primer pairs. The CPd DNA fragment (700 bp) from one of these samples was sequenced, showing 98.9% sequence identity with a TICV Japanese isolate (AB085603). Results of these assays suggest that in contrast to ToCV, TICV is not yet broadly established in France. This difference could be associated with the specificity of the vectors, since ToCV is transmitted by B. tabaci and T. vaporariorum, while TICV is transmitted only by T. vaporariorum (4). References: (1) R. H. Li et al. Plant Dis. 82:84, 1998. (2) D. Louro et al. Eur. J. Plant Pathol. 1065:589, 2000. (3) A. M. Vaira et al. Phytoparasitica 30:290, 2002. (4) G. C. Wisler et al. Plant Dis. 82:271, 1998.

Le TYLCV est un virus grave de la tomate qui sevit dans de nombreux pays, notamment dans le Sud de l'Europe. Ce virus appartient au genre Begomovirus de la famille des Geminiviridae; il est transmis par l'aleurode Bemisia tabaci selon le mode persistant. En France, un foyer a ete decouvert en Camargue en 1999 suite a une importation de plants contamines, puis eradique. Aucun cas n'a ete signale en 2000 ni en 2001. En revanche, d'importantes populations de B. tabaci ont ete identifiees en 2001 dans les Pyrenees-Orientales (P.O.), et la recherche du virus dans B. tabaci par hybridation moleculaire a mis en evidence une forte proportion d'insectes viruliferes. Au cours de l'ete 2002, des symptomes d'enroulement et de jaunissement ont ete observes sur tomate dans differents abris des regions PACA et Languedoc-Roussillon. Les prospections visuelles ainsi qu'un suivi par analyses ELISA ont mis en evidence une progression rapide du TYLCV dans une exploitation ou les plants avaient ete importes d'Espagne. Dans les P.O., zone ou B. tabaci sevit depuis 2001, seuls quelques cas ont ete detectes en fin d'ete. Le sequencage de differents isolats montre que seule l'espece TYLCV (ancienne espece TYLCV-Is) est presente. Les isolats 2002 presentent 98 a 99% d'identite de sequence avec differentes souches recemment caracterisees (souches espagnoles, Mexique, Republique dominicaine et Japon) ou plus anciennes (souches israeliennes). Ils different tres peu des isolats introduits en 1999 (99 a 100% d'identite de sequence). Depuis Juillet 2002, un arrete de lutte obligatoire impose la destruction des parcelles contaminees. Il sera important d'evaluer l'incidence de ces mesures sur l'evolution des populations virales. (Texte integral)

Tomato yellow leaf curl begomovirus (TYLCV) causes severe damage to tomato crops. The virus is not considered as established in France, although a single outbreak (subjected to eradication measures) occurred in 1999. Since the vector of TYLCV, the whitefly Bemisia tabaci, is already present in France and the virus is present in several neighbouring Mediterranean countries, there is a high risk of introduction into France. To prevent spread of the disease, systematic detection is essential. Samples of tomato and Eustoma grandiflorum were tested, and different methods were compared to determine which is the best for regular tests. Classical serological methods (TAS‐ELISA and immuno‐printing) were compared with molecular hybridization (which is specially suitable for the single‐stranded DNA genome of Geminiviridae), and PCR. Tissue‐printing methods, which avoid time‐consuming sample preparation, gave consistent results with hybridization. In contrast, immunoprinting detection confirmed only 61 % of samples found positive with TAS‐ELISA. Furthermore, a comparison of signal intensities obtained with TYLCV‐IL or TYLCV‐Sar probes provided indications on viral strain(s) detected. The efficiency, reliability and feasibility of serological and molecular techniques for routine official testing are discussed.