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Plant rhizosphere microbiomes are crucial for crops' health and productivity but the selection and specificity that govern crop microbiome assembly are not fully known. Herein, we examined bacterial communities of two cereals, durum (Triticum durum) and barley (Hordeum vulgare), and two legumes' species, chickpeas (Cicer arietinum) and bean (Faba been) under rainfed conditions and without fertilization practices. Our results demonstrate that microbiome composition and assembly are shaped predominantly by host species. Each species either cereals or legumes recruits a distinct rhizosphere microbiome, with the strongest host effect in Faba been. Moreover, crop microbiomes were dominated by a few dominant taxa belonging to Thaumarchaeota and Actinobacteria phyla, with Rhizobiales (Alphaproteobacteria) identified as the important biomarker taxa for both legumes. Our work provides comprehensive empirical evidence on host selection, potential sources, and enrichment processes for crop microbiome assembly, and has important implications for future crop management and manipulation of crop microbiome for sustainable agriculture.

Calls for ecological principles in agriculture have gained momentum. Intercropping systems have long been designed by growing two, or more, annual crop species in the same field, aiming for a better resource use efficiency. However, assembly rules for their design are lacking. Notably, it is still unknown whether species performances are maximized during both the vegetative and reproductive phases given the sensitivity of reproductive allocation rules to resource limitation. Interestingly, ecological theory provides expectations regarding putative invariance of plant reproductive allometry (PRA) under non-limiting conditions for plant growth. Here we examined whether and how PRA changes in response to plant-plant interactions in intercropping systems, which can inform both ecological theory and the understanding of the functioning of intercropping systems.We analyzed a dataset of 28 field cereal-legume intercropping trials from various climatic and management conditions across Western Europe. PRA was quantified in both mixing and single-species situations.PRA was positively impacted in specific management conditions, leading to a greater increase in yield for a given increase in plant size. Variations in PRA were more beneficial for legumes grown in unfertilized mixture, which explains their use as a key component in actual intercrop systems. The response for cereals was similar but less pronounced in magnitude, and was greater under limiting resource conditions. Focusing on intercropping conditions, hierarchical competition (indicated by biomass difference between intercropped species) appears as a strong driver of the reproductive output of a given species.Synthesis and applications. Plant reproductive allometry behaves in crop species in the same way as it does in wild species. However, contrary to theoretical expectations about an overall invariance of PRA, we highlighted taxon-specific and context-dependent effects of plant-plant interactions on PRA. This systematic deviation to PRA expectations could be leveraged to cultivate each species up to its reproductive optimum while accounting for the performance of the other, whether farmer’s objective is to favor one species or to reach an equilibrium in seed production. Sowing density and cultivar choice could regulate the biomass of each component, with specific targets derived from allometric relationships, aiming for an optimal reproductive allocation in mixtures.

In West and Central Africa, as in many regions of the world, vegetables are severely affected by geminivirus diseases. In Burkina Faso, observation of various virus-like symptoms, especially on tomato, suggests the involvement of several geminiviruses and underlines the pressing need for additional information on their diversity, distribution, prevalence and host plant reservoirs. Large-scale surveys conducted in Burkina Faso confirmed the presence of tomato (yellow) leaf curl diseases (ToLCD-TYLCD) and geminiviruses in all localities with mean prevalences of 25% and 45%, respectively. Five geminiviruses including four begomoviruses (pepper yellow vein Mali virus (PepYVMLV), tomato leaf curl Burkina Faso virus, tomato leaf curl Mali virus and tomato leaf curl Ghana virus) and a dicot-infecting mastrevirus (chickpea chlorotic dwarf virus) were characterized on tomato. In addition, PepYVMLV and cotton leaf curl Gezira virus (CLCuGeV) were characterized on pepper and okra, respectively, in combination or not with alphasatellites and betasatellites for CLCuGeV. The most severe, prevalent and widely distributed virus on vegetables was PepYVMLV, which was characterized for the first time in combination with a genetically divergent DNA-B component that may constitute a key factor of PepYVMLV pathogenicity. Of the eight weeds identified as potential reservoir hosts of begomoviruses, four host PepYVMLV. The results confirm the importance of geminivirus diseases on vegetable crops in Burkina Faso and highlight the complex association of geminiviruses and satellites. The detection of begomoviruses in weeds growing close to crops points to the increasing necessity to consider reservoir plants and virus communities in the control of virus diseases.

International audience; A novel geminivirus was identified in France and Spain in asymptomatic plants of white clover (Trifolium repens) and shrub medick (Medicago arborea). Its genome has the hallmarks of a capulavirus, and its relationship to other capulaviruses was confirmed by phylogenetic analysis. White clover isolates formed a tight cluster in the phylogenetic tree, while shrub medick isolates formed two distinct, more divergent groups with sequence identity values close to the species cutoff. These three groups have likely participated in recombination events involving alfalfa leaf curl virus and French bean severe leaf curl virus. The name "trifolium virus 1" (TrV1) is proposed for this new Capulavirus. Three TrV1 genotypes (TrV1-A, TrV1-B, and TrV1-C) were clearly distinguished.

Este libro convencerá al lector de la importancia de las frutas y hortalizas, y le hará ver que la producción a pequeña escala de estos cultivos es fundamental para alcanzar los objetivos de desarrollo sostenible. A lo largo de sus cinco capítulos, el lector conocerá los desafíos y las recompensas para los productores, los vendedores y los consumidores. Capítulo 1: definición práctica de las frutas y hortalizas, y justificación del apoyo a los pequeños agricultores y las cadenas de valor. Capítulo 2: opciones de manejo agrícola para garantizar que la producción sea sostenible, incluyendo recursos genéticos, sistemas de semillas, manejo del agua, suelo, nutrientes y control de las plagas y enfermedades. Capítulo 3: opciones para integrar a los pequeños agricultores comerciales que cultivan frutas y hortalizas en cadenas de valor socialmente inclusivas, lo que incluye servicios innovadores de manejo poscosecha, vínculos comerciales y reducción de la pérdida y el desperdicio de alimentos. Capítulo 4: opciones para que los profesionales y los responsables políticos de diferentes niveles gubernamentales, institucionales y sociales promuevan la producción y el consumo sostenibles de frutas y hortalizas seguras, nutritivas y asequibles. Capítulo 5: intervenciones e innovaciones clave para facilitar la producción sostenible de frutas y hortalizas en los países de rentas medias y bajas de todo el mundo. Esta publicación lleva al lector a un viaje, presentándole una diversa variedad de frutas y hortalizas a través de estudios de casos ilustrados de todo el mundo. Contiene argumentos a favor de la importancia de estos cultivos y anima a los lectores a desempeñar un papel activo tanto en la promoción de la producción de frutas y hortalizas como a la hora de alentar a la gente a consumirlas.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License.-- et al., [Background]: A number of molecular marker linkage maps have been developed for melon (Cucumis melo L.) over the last two decades. However, these maps were constructed using different marker sets, thus, making comparative analysis among maps difficult. In order to solve this problem, a consensus genetic map in melon was constructed using primarily highly transferable anchor markers that have broad potential use for mapping, synteny, and comparative quantitative trait loci (QTL) analysis, increasing breeding effectiveness and efficiency via marker-assisted selection (MAS). [Results]: Under the framework of the International Cucurbit Genomics Initiative (ICuGI, http://www.icugi.org), an integrated genetic map has been constructed by merging data from eight independent mapping experiments using a genetically diverse array of parental lines. The consensus map spans 1150 cM across the 12 melon linkage groups and is composed of 1592 markers (640 SSRs, 330 SNPs, 252 AFLPs, 239 RFLPs, 89 RAPDs, 15 IMAs, 16 indels and 11 morphological traits) with a mean marker density of 0.72 cM/marker. One hundred and ninety-six of these markers (157 SSRs, 32 SNPs, 6 indels and 1 RAPD) were newly developed, mapped or provided by industry representatives as released markers, including 27 SNPs and 5 indels from genes involved in the organic acid metabolism and transport, and 58 EST-SSRs. Additionally, 85 of 822 SSR markers contributed by Syngenta Seeds were included in the integrated map. In addition, 370 QTL controlling 62 traits from 18 previously reported mapping experiments using genetically diverse parental genotypes were also integrated into the consensus map. Some QTL associated with economically important traits detected in separate studies mapped to similar genomic positions. For example, independently identified QTL controlling fruit shape were mapped on similar genomic positions, suggesting that such QTL are possibly responsible for the phenotypic variability observed for this trait in a broad array of melon germplasm. [Conclusions]: Even though relatively unsaturated genetic maps in a diverse set of melon market types have been published, the integrated saturated map presented herein should be considered the initial reference map for melon. Most of the mapped markers contained in the reference map are polymorphic in diverse collection of germplasm, and thus are potentially transferrable to a broad array of genetic experimentation (e.g., integration of physical and genetic maps, colinearity analysis, map-based gene cloning, epistasis dissection, and marker-assisted selection)., This work was supported in part by SNC Laboratoire ASL, Ruiter Seeds B.V., Enza Zaden B.V., Gautier Semences S.A., Nunhems B.V., Rijk Zwaan B.V., Sakata Seed Inc, Semillas Fitó S.A., Seminis Vegetable Seeds Inc, Syngenta Seeds B.V., Takii and Company Ltd, Vilmorin & Cie S.A., and Zeraim Gedera Ltd (all of them as part of the support to the ICuGI); the grants AGL2009-12698-C02-02 from the Spanish "Ministerio de Ciencia e Innovación" to AJM. NK lab was supported in part by Research Grant Award No. IS-4223-09C from BARD, the United States - Israel Binational Agricultural Research and Development Fund, and in part by Israel Science Foundation Grant No. 386-06, De Ruiter Seeds, Enza Zaden, Keygene, Rijk Zwaan, Sakata Seed Corporation, Semillas Fitó, Syngenta Seeds and Vilmorin Clause & Cie. AD was supported by a JAE-Doc contract from "Consejo Superior de Investigaciones Científicas" (CSIC-Spain). MF was supported by a postdoctoral contract from CRAG. The research carried out at YX's laboratory was supported by Chinese funds (Grant No.2008-Z42(3), 5100001, 2010AA101907).

National audience

Description of the subject. Despite the importance of tomato in Central Africa, little is known about the weed flora occurring in tomato crops in this part of the world. Objectives. We aimed to provide a comprehensive description of the weed flora found in tomato crops in the mountainous region of South Kivu, DR Congo. Method. Floristic inventories were made in four cultivation zones of the Kabare territory, South Kivu. Results. In total, 79 species (belonging to 64 genera and 31 families) were recorded. The most species-rich families were Asteraceae and Poaceae. Therophytes and geophytes were the dominant life forms. Weed diversity was not significantly different between sites but species composition varied considerably, likely in relation to soil type. Based on the frequency and the abundance, the most problematic weeds were Commelina benghalensis, Galinsoga quadriradiata, Commelina diffusa, Galinsoga parviflora, Bidens pilosa, Oxalis debilis and Digitaria velutina.Conclusions. The weed flora in tomato fields of the mountainous regions of DR Congo is diversified, but only a few cosmopolitan species are problematic., Flore adventice de la tomate dans le Sud-Kivu montagneux, RD CongoDescription du sujet. En dépit de l’importance de la culture de tomates en Afrique centrale, peu d’études sur la flore adventice de cette culture y ont été réalisées.Objectifs. Cette étude visait à caractériser la flore adventice des cultures de tomates dans les régions montagneuses du Sud-Kivu, RD Congo. Méthode. Des inventaires floristiques ont été réalisés dans quatre zones de culture du territoire de Kabare, Sud-Kivu.Résultats. Au total, 79 espèces, réparties en 64 genres et 31 familles, ont été inventoriées. Les Asteraceae et les Poaceae constituent les familles les plus diversifiées. La flore est dominée par les thérophytes et les géophytes. La diversité spécifique était comparable entre les zones de culture, mais la composition en espèces y était variable. Sept espèces d’importance agronomique ont été identifiées : Commelina benghalensis, Galinsoga quadriradiata, Commelina diffusa, Galinsoga parviflora, Bidens pilosa, Oxalis debilis and Digitaria velutina.Conclusions. La flore adventice de la tomate dans les régions montagneuses du Sud-Kivu est diversifiée. Néanmoins, les quelques espèces problématiques sont des espèces cosmopolites.

This chapter focuses on protected cultivation (PC), defined as the protection of crops against adverse climatic and biological factors using physical means. As natural resources become scarcer, farm inputs become more expensive and consumers more attentive to the sanitary and nutritious aspects of food produced, PC has become one promising yet improvable way to address these challenges. As the global demand for high value crops, such as vegetables, increases, PC appears an opportunity for farmers to increase their income, improve their working conditions and secure their production, thereby attracting youth to enter the crucial but aging farming sector. In Sub-Saharan Africa, farmers constantly face the threat of losing their crops due to pests, diseases or harsh climatic conditions, with no insurance to cover their loss. A case study, comparing PC of tomatoes in Benin and Tanzania, showed that PC is profitable despite high initial investments, provided there is a market for high quality produce. Favourable policies, farmers' training and agronomic research are prerequisites to the adoption and development of PC technologies and techniques in Sub-Saharan Africa. PC has the potential to enhance bioeconomy in the region and at the same time achieve some of the SDGs.

During the fall of 2003, mild mosaic symptoms were observed in melon (Cucumis melo L.) plants grown in glasshouses near Eyragues (southeastern France) resembling those caused by the Bemisia tabaci transmitted Cucumber vein yellowing virus (CVYV, genus Ipomovirus, family Potyviridae). In addition, large numbers of B. tabaci were observed to be colonizing these crops. The identification of CVYV was established through differential host range reaction, immunosorbent electron microscopy (IEM), and reverse transcription (RT)-PCR experiments. Crude sap from symptomatic leaves was used to inoculate differential host plants. Mild mosaic symptoms were observed on melon, and cucumber developed vein-clearing symptoms typical of CVYV. No symptoms were observed in Chenopodium quinoa, C. amaranticolor, Nicotiana benthamiana, N. tabacum, and Vigna sinensis. Numerous, slightly flexuous, elongated virus particles were observed in infected plant extracts; these particles were decorated by a polyclonal antiserum raised against a Sudanese CVYV isolate. To confirm CVYV identification, total RNA extracts (TRI-Reagent, Sigma Chemical, St. Louis, MO) were obtained from the original symptomatic melon tissues. RT-PCR was carried out using CVYV-specific primers CVYV-CP-5′: 5′-GCTTCTGGTTCTCAAGTGGA-3′ and CVYV-CP- 3′: 5′-GATGCATCAGTTGTCAGATG-3′ designed according to the partial sequence of the coat protein gene of CVYV-Isr (GenBank Accession No. AF233429) (2). A 540-bp fragment corresponding to the central region of CVYV coat protein was amplified from total RNA extracted from symptomatic but not from asymptomatic melon tissue. Direct sequencing was done on RT-PCR products (GenBank Accession No. EF441272). The sequence was 95 and 99% identical to that reported for CVYV isolates from Israel and Spain, respectively. CVYV was first described in Israel and has recently emerged as the cause of important diseases in Spain and Portugal (1,3). Shortly after detecting CVYV during 2003, efforts were made to eradicate the virus in susceptible crops. CVYV was not detected again during intensive surveys conducted in southeastern France during 2004, 2005, and 2006, suggesting that the CVYV detected during 2003 resulted from an accidental introduction and that the virus has not become established in France. References: (1) I. M. Cuadrado et al. Plant Dis. 85:336, 2001. (2) H. Lecoq et al. J. Gen. Virol. 81:2289, 2000. (3) D. Louro et al. Plant Pathol. 53:241, 2004.

L'utilisation de pesticides n'est pas sans impact sur l'environnement ni sur la sante humaine. La societe civile mauricienne s'est recemment emparee de la question suite a des detections de pesticides dans des legumes preleves dans les marches de l'ile. Mais quelles sont les marges de manœuvre des producteurs pour faire face a cette demande societale ? Comme les methodes de production etaient jusqu'ici peu documentees, nous avons mene une enquete aupres de 298 producteurs de legumes afin d'analyser leurs pratiques phytosanitaires et d'en evaluer les impacts sur l'environnement. Cette enquete vise a repondre aux questions suivantes : Quels sont reellement les usages de pesticides des producteurs ? Quelles contraintes supportent-ils ? Les producteurs sont plutot âges (60 % ont plus de 50 ans) et peu d'entre eux ont une formation initiale de base. Pres des deux tiers d'entre eux ne sont pas proprietaire du foncier. Dans ces conditions, les producteurs pratiquent une agriculture d'opportunisme visant a optimiser leur parcelle dans le temps et dans l'espace. Aucun risque, aucune perte. La grande majorite des producteurs protegent leurs cultures par des traitements phytosanitaires preventifs contre les nombreux bio-agresseurs recenses. Entre 11 et 53 traitements par an sont ainsi effectues selon les successions culturales entreprises. Pres de 60 insecticides et fongicides sont couramment utilises par les producteurs. L'outil d'aide a la decision « Phyto'Aide » nous a permis d'evaluer, ex ante, le risque du transfert de ces substances vers l'environnement. Ces risques s'averent importants pour tous les pesticides car les bonnes pratiques phytosanitaires sont peu ou pas respectees par les producteurs. Dans ces conditions, de nouvelles strategies de protection contre les bioagresseurs s'averent necessaires. Nous proposons dans cet article differentes pistes d'amelioration, mais aussi une strategie d'accompagnement de ces producteurs pour faire face a une demande societale d'une production saine et sure.

Agri-chains alter the trajectories of territorial development. Approaches focused on sustainable territorial development insist that local actors should have control over development and be allowed to orient it. It is a matter of understanding how local communities organize themselves or mobilize existing organizations to develop a collective project that can resolve the contradictions between the economic, environmental, and social dimensions of development. Three cases studied in Vietnam are presented here. They illustrate the significance of the local presence of traders and agro-industries, more so than that of the appropriation by farmer communities themselves of the issues of the development of these agri-chains. In this process, alliances between companies, farmers, and local authorities play a crucial role in the emergence of innovations. The challenge is for the local territorial actors, with the support of incumbent territorial organizations and State services, to participate collectively in the governance of agri-chains to solve the problems caused by the rapid growth of private firms.

Les insectes et les acariens constituent des ravageurs importants des cultures maraîchères dans toutes les régions tropicales du monde, dont les îles de l'Outre-mer français et les territoires proches. L'épandage d'insecticides et d'acaricides n'a résolu que temporairement les problèmes rencontrés et aujourd'hui, les méthodes de protection agro-écologique des cultures sont recommandées. Elles mettent en oeuvre la prophylaxie, la lutte physique, la lutte biotechnique et la lutte biologique. La reconnaissance des différents ravageurs et des " utiles " est la première étape de la lutte biologique. Cet ouvrage s'efforce de faciliter cette tâche, en décrivant les principaux groupes d'arthropodes en 22 fiches : d'une part, les ravageurs, d'autre part, les ennemis naturels, prédateurs et parasitoïdes. La bio-écologie de ces groupes et les moyens existants pour contrôler les ravageurs sont détaillés avec de nombreuses photos à l'appui. L'objectif de cet ouvrage est également de comprendre le développement des ravageurs et des " utiles " dans les cultures et de mieux gérer les moyens limitant leurs populations. Cela permettra de mettre en oeuvre la lutte biologique, via des prédateurs et des parasitoïdes, et des pratiques agro-écologiques, comme l'utilisation de plantes de service, qui augmentent la diversité biologique et participent à la régulation des populations des ravageurs des agrosystèmes. Cet ouvrage facile à aborder est destiné aux professionnels du maraîchage, particulièrement en zone tropicale, et aux conseillers et techniciens des pratiques agro-écologiques.

Les filières agroalimentaires modifient les trajectoires de développement des territoires. Les approches en termes de développement territorial durable insistent sur l'appropriation du pilotage du développement par les acteurs locaux. Il s'agit de comprendre comment les communautés locales s'organisent ou mobilisent les organisations existantes pour élaborer un projet collectif qui permette de résoudre les contradictions entre dimensions économiques, environnementales et sociales du développement. Les trois situations étudiées au Vietnam sur des liens entre filières et territoires illustrent le rôle de l'implantation locale des acteurs du commerce et de l'agro-industrie, plus que celui de l'appropriation par les communautés paysannes ellesmêmes des enjeux du développement de ces filières. Dans ce processus, les alliances entre firmes, paysans et autorités locales jouent un rôle crucial dans l'émergence d'innovations. L'enjeu est que les acteurs des territoires locaux, relayés par des organisations territoriales historiquement constituées et les services de l'État, puissent participer collectivement à la gouvernance des filières afin de résoudre les problèmes induits par l'essor rapide des firmes privées.

Guide de référence du jardinage sous les tropiques, Mon jardin tropical, vous apprendra à cultiver près de 550 espèces à travers 504 pages et 763 photographies ; que vous soyez aux Antilles, en Guyane, à la Réunion... ou en Europe !

International audience; Background and aims. Positive below-ground interactions (facilitation) should be more pronounced when resources limit crop growth, according to the stress-gradient hypothesis. Our aim was to test this hypothesis for intercropped durum wheat and faba bean along a P-fertilizer gradient. Methods. A field experiment was conducted in a long-term P-fertilizer trial with three rates of P-fertilization (No, Low and High P). Microbial biomass was assessed by chloroform fumigation-extraction. Quantitative PCR was applied to evaluate the abundance of relevant microbial groups. Results. Phosphorus availability and microbial biomass systematically increased in the rhizosphere compared to bulk soil. P-fertilization resulted in higher abundance of targeted bacterial phyla, whole bacterial and fungal communities, and depressed mycorrhizal colonization of durum wheat, but not faba bean. Microbial biomass carbon significantly increased in the rhizosphere only in P-fertilized treatments, pointing to P limitation of microbial communities. Intercropping yielded a significant effect on rhizosphere microbial properties only at High P. Microbial biomass P increased in the rhizosphere of intercropped faba bean only at No P level, and was thus the sole finding supporting the stress-gradient hypothesis. Conclusions. P-fertilization was the main driver of microbial communities in this field trial, and P-fertilizer application modulated the species-specific effect in the intercrop. Plant performance did not validate the stress-gradient hypothesis as positive plant-plant interactions occurred regardless of the level of P-fertilization.

International audience; Since 1999, “emerging” (EM) strains of Watermelon mosaic virus (WMV) have been detected in cucurbit crops of southeastern France, probably as a result of recent introductions. Population genetic approaches were used to study the structure of EM isolates in southeastern France and to identify factors involved in their spatial distribution. A population clustering method (SAMOVA) and a maximum-difference algorithm (Monmonier's algorithm) were combined to visualize and quantify barriers to gene flow between populations. Both methods yielded similar results and two main barriers were identified. A North/South oriented barrier may be related to physical obstacles to gene flow (Rhône River, presence of an area with few cucurbit crops). Although the barrier was very strong, some “crossing” events were detected. A second barrier, oriented Northwest to Southeast, was not correlated with obvious geographical features. The two methods used here are complementary and confirm the limited spread of WMV-EM isolates. This approach can be useful in epidemiology studies to characterize the structure of viral populations and identify barriers to gene flow.

International audience; Botrytis cinerea is able to build-up resistance to pyrrolnitrin, an antibiotic produced by diverse biocontrol agents, possibly compromising the durability of this method of disease control. The development of two near-isogenic lines of B. cinerea differing in their level of resistance to pyrrolnitrin was compared in tomato plants and on PDA medium. In tomato plants, significant differences in the percentage of infected petioles 1 day after inoculation and in symptom progression on petioles and stems were observed between the resistant mutant and the sensitive wild-type parent, suggesting a difference in their level of aggressiveness. Cytohistological investigations revealed that conidia of both near-isogenic lines germinated 6 h after inoculation and mycelium developed within petiole tissues 12 h after inoculation. However, while the wild-type parent isolate spread throughout the petiole and rapidly invaded the stem tissues via the leaf-abscission zone 72 h after inoculation, the pyrrolnitrin-resistant mutant failed to extend beyond petiole tissues to invade the stem. Moreover, 72 h after inoculation, the mycelial development of the pyrrolnitrin-resistant mutant was accompanied by abnormal glycogen accumulation and chlamydospore-like cell formation. In contrast, wild-type parent mycelium was normally structured with intensive colonization of stem tissues. Additionally, on PDA medium the mycelium of the pyrrolnitrin-resistant mutant was less vigorous than the wild-type isolate. These results suggest that the acquisition of pyrrolnitrin-resistance in B. cinerea is accompanied by changes in mycelial structure and reduction in mycelial growth, leading to a noticeable loss of aggressiveness on tomato plants.

International audience; A mechanistic model predicting the accumulation of tomato fruit sugars was developed in order (i) to dissect the relative influence of three underlying processes: assimilate supply (S), metabolic transformation of sugars into other compounds (M), and dilution by water uptake (D); and (ii) to estimate the genetic variability of S, M, and D. The latter was estimated in a population of 20 introgression lines derived from the introgression of a wild tomato species (Solanum chmielewskii) into S. lycopersicum, grown under two contrasted fruit load conditions. Low load systematically decreased D in the whole population, while S and M were targets of genotype×fruit load interactions. The sugar concentration positively correlated to S and D when the variation was due to genetic introgressions, while it positively correlated to S and M when the variation was due to changes in fruit load. Co-localizations between quantitative trait loci (QTLs) for sugar concentration and QTLs for S, M, and D allowed hypotheses to be proposed on the processes putatively involved at the QTLs. Among the five QTLs for sugar concentration, four co-localized with QTLs for S, M, and D with similar allele effects. Moreover, the processes underlying QTLs for sugar accumulation changed according to the fruit load condition. Finally, for some genotypes, the processes underlying sugar concentration compensated in such a way that they did not modify the sugar concentration. By uncoupling genetic from physiological relationships between processes, these results provide new insights into further understanding of tomato fruit sugar accumulation.

Botrytis cinerea, the causal agent of grey mould, is considered as a major burden on greenhouse tomato production. In heated greenhouses, where leaf pruning is a routine practice and microclimatic conditions are favourable for grey mould development, infections of the pruning wounds result in stem cankers that can rapidly kill the plants. Chemical control is not always sufficiently effective and growers face increasing demands for reducing their dependency on pesticides. Several techniques can be used for the removal of leaves. They differ mainly on the presence or absence and the size of petiole stubs remaining on the stems after pruning. In this study, leaf pruning techniques were compared in an experimental greenhouse and the results validated in four commercial greenhouses, in a variety of agronomic conditions and in various situations of inoculum pressure. All experiments clearly showed that a careful removal of the leaves without leaving any petiole stubs on the stems can significantly decrease the incidence of stem cankers even under high disease pressure. As up to 10-fold differences were observed, this suggests the possibility of improving pruning practices in tomato greenhouses by removing leaves systematically close to the stem. This environmentally-friendly cultural practice appears compatible for integration with other preventative methods for the objective of sustainable crop protection in greenhouse tomatoes.

This study presents an analysis of air circulation and microclimate distribution during daytime in a 1-hectare Canary type tomato greenhouse in the coastal area of southern Morocco. The investigation of the climate inside the greenhouse is based on a numerical simulation using a finite volumes method to solve the mass, momentum and energy conservation equations. The main novelty of this simulation lies in the realism of the 3D modelling of this very large agricultural structure with (i) a coupling of convective and radiative exchanges at the surface of the plastic roof cover, (ii) simulation of the dynamic influence of the insect screens and tomato crop on airflow movement, using the concept of porous medium, (iii) simulation, in each grid cell of the crop canopy, of the sensible and latent heat exchanges between the greenhouse air and the tomato crop, and (iv) detailed simulation of climate parameters in a 1-hectare real-scale commercial greenhouse. The model simulations were first validated with respect to temperature and relative humidity fields measured inside the experimental greenhouse for fairly steady-state outside conditions marked by a prevailing sea breeze around the solar noon. A good agreement was observed between the measured and simulated values for inside air temperatures and specific humidity. It was next used for exploring the details of the inside air temperature and humidity fields and plant microclimates and transpiration fluxes throughout the greenhouse space. Simulation for a wind direction perpendicular to the side and roof openings shows that the insect screen significantly reduced inside air velocity and increased inside temperature and humidity, especially in the vicinity of the crop canopy. It revealed the details of the flow field within the greenhouse. At the windward end of the greenhouse, the flow field was marked by a strong windwise air current above the tomato canopy which was fed by the wind ward side vent, and a slow air stream flowing within the tomato canopy space. Then, from the first third of the greenhouse to the leeward end, the flow field was marked by the combination of wind and buoyancy forces, with warmer and more humid inside air which was evacuated through the upper roof vents, while colder and dryer air was penetrated through the upper roof vent openings. Based on these simulations, design studies of the greenhouse crop system were performed to improve inside air temperature and humidity conditions by simple modifications of orientation of the crop rows

International audience; Virus-resistant transgenic plants have been created primarily through the expression of viral sequences. It has been hypothesized that recombination between the viral transgene mRNA and the RNA of an infecting virus could generate novel viruses. As mRNA/viral RNA recombination can occur in virus-resistant transgenic plants, the key to testing this risk hypothesis is to compare the populations of recombinant viruses generated in transgenic and non-transgenic plants. This has been done with two cucumoviral systems, involving either two strains of cucumber mosaic virus (CMV), or CMV and the related tomato aspermy virus (TAV). Although the distribution of the sites of recombination in the CMV/CMV and TAV/CMV systems was quite different, equivalent populations of recombinant viruses were observed in both cases. These results constitute the first comparison of the populations of recombinants in transgenic and non-transgenic plants, and suggest that there is little risk of emergence of recombinant viruses in these plants, other than those that could emerge in non-transgenic plants

International audience; The geographic range of plant pests can be modified by the use of glasshouses. Bemisia tabaci, originating from warm to hot climates, has been shown to be a complex of distinct genetic groups with very limited gene flow. The genetic structure of this pest was studied in glasshouses in southern France, a region beyond the northern limit of its open-field development area in Europe. Seven microsatellite loci were scored in 22 populations sampled from various regions over 3 years. Two genetic groups were distinguished using a Bayesian clustering method and were assigned to the socalled biotypes B and Q using the gene sequence of cytochrome oxidase 1 (CO1). All but one population corresponded to biotype Q, even though only biotype B was previously reported. Despite the enclosed environment of glasshouses and their expected isolation due to low outdoor survival during the winter, only limited differentiation among biotype Q glasshouses was observed. A single sample site was notable for a decrease in expected heterozygosity and the mean number of alleles over the years. The lack of spatial genetic structure among biotype Q populations was indicative of a recent colonization event combined with large dispersal at all spatial scales. This migration pattern of biotype Q populations was further supported by additional CO1 sequences, since individuals from France, Asia and America exhibited 100% nucleotide identity. The evolution of genetic diversity observed in glasshouses in France is part of the worldwide invasion of biotype Q, which is discussed in light of human activities. Heredity (2008) 100, 316–325; doi:10.1038/sj.hdy.6801080; published online 12 December 2007

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Market gardeners are facing new environmental, commercial and safety requirements and regulations that weigh heavily on their crop planting and management decisions. Producing high-quality products and simultaneously reducing the use of chemical products needs change in the multi-field planning of crops. In order to identify which cropping practice may be altered depending on each farm's characteristics, we built a rule-based model that represents how market gardeners plan cropping cycles of lettuce and endive, here denoted as salad vegetables, on a farm scale. The model is adapted to the specificities of salad vegetable crops in the Mediterranean region, in particular the combination of several cycles per year and of open field and sheltered crops. The output variables are the developed areas allocated to the different salad types and the range of the harvest dates, which are two key factors for commercialisation. The model is based on identifying the successive decision steps of growers when building their farming systems; descriptive variables are the effective surface area and period for salad cultivation, the number of salad cycles per year, the developed surface area of each salad type and the dates of harvest. The decision-making rules leading to each descriptive variable are based on the agronomic characteristics of soil, climate and crops, farmers' strategic objectives and organisation of farm resources. The cropping decisions were recorded in 38 farms in the large market-gardening region of Languedoc-Roussillon. In the sample, the number of salad types cultivated per farm varied from 1 to 8 and the harvesting period from 3 to 7 months. Our results demonstrate that the model can explain a substantial part of this variability, 26 and 28 farms among 38, respectively, being correctly classified by the model for the two variables. The original result of this work is to enhance the generality of a similar framework built earlier for arable cropping systems. From a practical point of view, this model can be used to determine the leeway available to the farmers for the introduction of technical change in salad cropping. It could therefore be used by agricultural advisors to plan salad crops either for individual farms or on the scale of a marketing structure.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; Knowledge of radionuclide or trace element retention and translocation to plants following an aerial contamination event, for example, sprinkling with contaminated water, is necessary for the evaluation of human exposure through consumption of contaminated vegetables. The fate of 63Ni and 109Cd in all plant parts of three different vegetables after wet deposition on leaves or on fruits was studied. Lettuce (Lactuca sativa L.), radish (Raphanus sativus L.), and bean (Phaseolus vulgaris L.) grown under controlled conditions in a growth chamber were contaminated with 63Ni and 109Cd either on leaves, by means of two different contamination methods (a single early contamination and a repetitive one), or on bean husks (third contamination method: a single contamination at a late stage). Spiked and nonspiked organs were harvested at maturity and radionuclide contents were measured. The fraction retained was on average 56% of the initially administered doses of 63Ni and 87% of 109Cd. The leaf-to-other organ translocation factor was considerably higher for 63Ni (on average 43% of retained radioactivity) than for 109Cd (8%). Nickel-63 migrated throughout the whole plant following foliar contamination, and mainly toward young leaves, seeds in formation, and sink organs, whereas 109Cd migrated to a much lesser extent and only to the organs that were closest to the spiked one, and not at all into fruit. After a fruit contamination event, both radionuclides were translocated into the seeds of spiked fruits. Radionuclide retention and translocation were not affected by plant species, but principally by the type of organ contaminated.

International audience; The dominant gene Am from Lycopersicon hirsutum f. sp. glabratum PI134417 confers resistance to most strains of Alfalfa mosaic virus, including the recently identified necrotic strains. The phenotypic response includes a lack of symptom development following mechanical inoculation of leaves. To study the resistance mechanism controlled by Am, biological (back-inoculation to susceptible hosts), serological (double-antibody sandwich, enzyme-linked immunosorbent assay), and molecular (reverse transcription-polymerase chain reaction and hybridization with specific riboprobes) methods of virus detection have been conducted on mechanically inoculated PI134417 leaves. The virus was never recovered, indicating that Am acts by an inhibition of viral accumulation during the early events of the virus life cycle. Am has been mapped genetically to the short arm of tomato chromosome 6 in the resistance hotspot, which includes the R-genes Mi and Cf-2/Cf-5 and the quantitative resistance factors Ty-1, Ol-1, and Bw-5.

International audience; Papaya ringspot virus (PRSV) and Zucchini yellow mosaic virus(ZYMV) are potyviruses frequently reported in cucurbits in Mediterranean, subtropical, and tropical regions. Occasionally, epidemics are also observed in more temperate regions, but the ways these viruses are introduced into new areas are not yet fully determined. We investigated the possibility that infected imported melon fruit could be a route for the introduction of PRSV and ZYMV. Imported melon fruits of the yellow canary type infected by ZYMV and PRSV were exposed in the fields next to healthy melon or squash bait plants. During this period, aphids were observed landing and probing on the fruits. In four independent experiments using different fruits, 3.1 to 25% of bait plants were infected by ZYMV and/or PRSV. PRSV was more frequently transmitted to bait plants than ZYMV. Comparison of partial sequences of the isolates from fruits and from bait plants showed a very high, if not complete, identity within each experiment, confirming that a natural transmission did occur from the fruit to the bait plants. These results suggest that globalization of melon production and international trade may be a factor in the spread of cucurbit potyviruses between countries or continents.

The taxonomy of the genus Manihot is still uncertain and the genetic origin of cassava (M. esculenta Crantz) continues to be controversial. We studied the degree of genetic relatedness between cassava and two naturally occurring species (M. flabellifolia and M. peruviana) which are probably involved in the evolution of cassava, using RAPD and AFLP molecular markers. Thirty-three clonal accessions of cassava of known genetic diversity and 15 accessions of the wild species M. flabellifolia and M. peruviana were analyzed using 92 polymorphic RAPD bands and 73 polymorphic AFLP bands. The genetic markers were unable to differentiate the two wild species, which confirms their botanical similarity. Half of the total number of amplified bands were monomorphic in all of the genotypes evaluated. The mean genetic similarity (Jaccard) between cassava and the species M. flabellifolia/M. peruviana was 0.59. A grouping analysis (neighbor-joining method) with RAPD markers of cultivated cassava, M. flabellifolia/M. peruviana and the other wild species located the genotypes of cassava and M. flabellifolia/M. peruviana at one extremity and the three Mexican species (M. aesculifolia, M. michaelis and M. chlorostica) at the other. An intermediate position between these groups was occupied by two wild species (M. glaziovii and M. reptans) native to central and northeastern Brazil. These results are consistent with the hypothesis that the species M. flabellifolia and M. peruviana gave rise to the cultivated species.A taxonomia do gênero Manihot em grande parte não está resolvida e a origem genética da mandioca (M. esculenta Crantz) continua controvertida. Na tentativa de contribuir para elucidar sua história evolutiva, as relações de proximidade genética da mandioca com duas espécies selvagens que provavelmente participaram da sua história evolutiva, M. flabellifolia e M. peruviana, foram estudadas através de dois tipos de marcadores moleculares, os RAPDs e os AFLPs. Para tanto, foram empregados 33 acessos clonais de mandioca de reconhecida diversidade genética e 15 acessos das espécies selvagens M. flabellifolia e M. peruviana das regiões central e norte do Brasil, importantes centros de ocorrência natural destas espécies. Noventa e duas bandas polimórficas RAPD e 73 AFLP foram utilizadas para análise dos resultados. Ambos marcadores foram incapazes de diferenciar as duas espécies selvagens utilizadas, confirmando a grande semelhança botânica entre elas. Em relação à mandioca cultivada, os resultados revelaram grande proximidade genética entre estas e as espécies selvagens. Metade do total de bandas amplificadas apresentaram-se monomórficas entre todos os genótipos avaliados. O valor médio de similaridade genética (Jaccard) entre a mandioca e as espécies M. flabellifolia/M. peruviana é de 0.59. As relações de proximidade genética entre a mandioca e M. flabellifolia/M. peruviana foram confirmadas quando outras cinco espécies selvagens foram também incorporadas em relação ao polimorfismo gerado pelos RAPDs. A análise de agrupamento (neighbor-joining) realizada com genótipos de mandioca, de M. flabellifolia/M. peruviana e das demais espécies selvagens reuniu numa extremidade os genótipos de mandioca e M. flabellifolia/M. peruviana e na outra extremidade três espécies mexicanas (M. aesculifolia, M. michaelis e M. chlorostica). Entre estes dois grupos se posicionaram outras duas espécies selvagens cuja ocorrência natural é na região central e no nordeste brasileiro (M. glaziovii e M. reptans). Embora não conclusivos, os resultados apresentados são coerentes com a hipótese de que as espécies M. flabellifolia e M. peruviana poderiam ter originado a espécie cultivada. No entanto, outras espécies pouco estudadas (M. procumbens, M. fruticulosa, M. pentaphylla e M. pruinosa) foram recentemente citadas como geneticamente muito próximas da mandioca. Assim, um estudo abordando maior número de espécies e com marcadores mais apropriados, a exemplo dos microsatélites, merece ser feito.

This work focuses on the genetic diversity of American cassava through RAPD molecular markers. The 126 genotypes studied were distributed on four geographical levels ranging from local to continental. Samples included ethnocultivars from the Santa Isabel community in the Brazilian Amazon, local cultivars collected in the State of São Paulo, native accessions from very diverse Brazilian regions, and representative accessions from the Centro Internacional de Agricultura Tropical (CIAT) core collection. Eighty-eight polymorphic bands were analyzed. Results revealed the weak genetic structure of the cassava analyzed. The pattern formed by the first two axes of the principal coordinates analysis (PCoA) revealed an overlapping of the São Paulo State genotype, the Brazilian group and the core collection accessions. The Santa Isabel ethnocultures formed a separate group. The weak genetic structure of cassava can be explained by the common practice of exchanging botanical material among small producers as well as by recombinations among genotypes. When the genotypes were analyzed using climatic data, the sample sites were found to be structured according to temperature and precipitation. RAPD markers proved very useful in the genetic diversity study, resulting in important implications for cassava germ plasm collections and genetic breeding.Este trabalho enfoca a diversidade genética de mandiocas americanas através de marcadores moleculares do tipo RAPD. Os 126 genótipos estudados estão distribuídos em quatro escalas geográficas, indo do local ao continental, ou seja, etnocultivares de uma comunidade chamada Santa Isabel, na Amazônia brasileira, cultivares locais coletados no Estado de São Paulo, um grupo representado por acessos oriundos das mais diversas regiões brasileiras e acessos representantes da "core collection" do CIAT. Oitenta e oito bandas RAPD polimórficas foram retidas para as análises. A estrutura genética das mandiocas deste estudo revelou-se fraca. O plano formado pelos dois primeiros eixos da análise de coordenadas principais (PCoA) revelou sobreposição dos genótipos do Estado de São Paulo, do grupo Brasil e dos acessos da "core collection". Por outro lado, os etnocultivares de Santa Isabel mostraram-se estruturados num grupo a parte com relação aos demais genótipos. Além disso, os etnocultivares de Santa Isabel apresentaram importante diversidade genética em relação aos genótipo dos outros três grupos. A fraca estrutura genética das mandiocas cassava pode ser explicada pelas trocas de material botânico entre pequenos produtores, prática normalmente empregada, assim como recombinação entre genótipos, visto que a mistura de diferentes cultivares em uma mesma parcela de cultura é também uma prática usada por pequenos produtores. Entretanto, quando os genótipos foram analisados em função de dados climáticos das localidades de origem dos mesmos, pudemos evidenciar uma estruturação em função da temperatura e da precipitação destes locais. Os marcadores RAPD mostraram-se informativos para o estudo da diversidade genética de mandiocas, oferecendo indicações importantes para a coleta de germoplasma de mandioca, assim como para o seu melhoramento genético. Com relação à importante diversidade genética encontrada na comunidade de Santa Isabel, outros estudos, através de outros marcadores e com genótipos de outras localidades, precisariam ser realizados para se tirarem conclusões mais diretas a respeito desta variabilidade.

La relation entre la vitesse relative de croissance de la matière fraîche et la teneur en azote réduit dans cette même matière fraîche a été étudiée entre le semis et la maturité commerciale chez la laitue cultivée sous abri pour deux cultures : l’une en été et l’autre en automne. Pour chaque saison, quatre traitements (deux niveaux nutritionnels croisés avec deux niveaux lumineux) ont été appliqués à des plantes ferti-irriguées en conditions de hors-sol sur sable. Le niveau de rayonnement ne montre pas d’effet sur la relation entre la VRC et la teneur en azote réduit. À même teneur en azote, les vitesses relatives de croissance d’été sont doubles de celles de l’automne. Les relations saisonnières deviennent semblables si la vitesse relative de croissance, qui présente une relation linéaire positive avec la température, est calculée en fonction de la durée exprimée en degré.jour. Ces résultats soulignent l’importance conjointe de la température et de la teneur en azote réduit dans l’établissement d’une vitesse relative de croissance., The relation between relative growth rate of fresh matter and reduced nitrogen content in this fresh matter was studied during the growth of the lettuce in summer and in autumn. Four treatments for each season: two nutrional levels and two radiation levels have been applied to plants fed with nutrient solution and grown in sand in a plastic greenhouse. The level of radiation has no effect on the relation between the relative growth rate and the nitrogen content. For the same nitrogen content the relative growth rate in summer expressed in d- a1ywas twice that in autumn. They became the same if the relative growth rate, which correlates positively with temperature, was calculated over time expressed in degree.day. These results show the importance of nitrogen content and temperature on the determination of the relative growth rate.

Poster présenté au 7. Meeting of IOBC-WPRS working group "Induced resistance in plants against insects and diseases": leaping from success in the lab to success in the field, Avignon, FRA (2013/06/10-13); International audience; In this paper we describe our strategy to unravel the connection between plant defenses and plant resistance to pests. With tomato (Solanum lycopersicum) as the reference plant, our ambition is to screen different plant defense stimulators (SPD) and measure (i) the resulting protection leve! towards Phytophthora parasitica, Botrytis cinerea and Oïdium neolycopersici (ii) the genes involved in the corresponding defense mechanisms (iii) the proteins and secondary metabolites which could be effector of resistance. We already show that BABA induces a strong resistance to P. parasitica (100% protection, no symptoms). Conversely, SA does not protect tomato to P. parasitica infection even though some classical defense genes are highly up-regulated in the same manner after BABA and SA treatments. Preliminary results of RNA-Seq evidence that the expression of more than 1000 genes is modified by BABA treatment. The possible involvement of unreported functions is discussed.

La réussite des cultures de cucurbitacées est souvent menacée par les virus tels que le CMV, le CABYV, le ZYMV et le WMV. Il y a quelques années, une résistance à la transmission de ces virus par le puceron Aphis gossypii et au puceron lui-même associée au gène Vat a été mise en évidence. Mais des contournements de ce gène sont à craindre en raison de la forte pression de sélection exercée par les variétés de melon résistant. Cette année, deux essais aux champs ont été implantés à Montfavet et à Moissac afin de déterminer l’incidence du gène Vat sur la dissémination des virus et d’étudier l’influence de pratiques culturales sur la résistance. Une efficacité partielle du gène Vat a été observée pour le CABYV, laissant supposer que le vecteur principal de ce virus est A. gossypii. Ces résultats confirment les études antérieures. Cependant, l’essai au champ n’a pas permis de mettre en évidence une efficacité nette de la bande enherbée ou de la bande fleurie comme protection de culture contre les virus., The success of cucurbits crops is often threatened by viruses such as CMV, CABYV, ZYMV and WMV. A few years ago, a specific resistance transmission of these viruses by the aphid Aphis gossypii and the aphid itself associated to Vat gene has been discovered. But breakdowns of this gene are worrying because of the strong selection pressure applied by melon varieties resistant. This year, two field trials were settled at Montfavet and at Moissac to determine the impact of Vat gene on the spread viruses and to study the influence of cultural practices on resistance. The partial efficiency of Vat gene was observed for CABYV, suggesting that the main vector of this virus is A. gossypii. These results are consistent with previous studies. However, the field trial failed to demonstrate a clear efficiency of grass or flowers strips as crop protection against the viruses.

Poster présenté au 6. IOBC-WPRS Meeting of the working group "Induced resistance in plants against insects and diseases". PR-proteins and induced resistance against pathogens and insects; 2011/09/04-08 ; Neuchatel (CHE); International audience; Powdery mildew caused by Podosphaera xanthii and Golovinomyces cichoracearum is one of the principal diseases on cucurbit crops in temperate climates. In order to control this disease, various biological methods, including induced resistance by the use of extracts from Fallopia sachalinensis, have been identified. This study was conducted to characterise the diversity of susceptibility to this plant extract among 52 isolates of P. xanthii and 5 isolates of G. cichoracearum collected from various cucurbit species in different production areas. To this end, disks excised from melon leaves were soaked in a preparation of F. sachalinensis extract (1% w/v) or in a control solution, inoculated with fresh conidia of powdery mildew 24 hours after treatment and placed in a growth chamber. Ten days after inoculation, symptoms were rated in classes based on a visual estimation of the leaf area infested by powdery mildew. Additionally, spore production on the leaf disks was assessed. The plant extract significantly decreased the severity of disease for all the powdery mildew isolates tested. On average, spore production was only ca. 20% in presence of the plant extract relative to the untreated control. However, the extent of the reduction in spore production variedwidely among isolates.

The development of BCAs represents an attractive alternative to fungicides for the protection of crops against plant pathogens but the durability of this method has not been studied in details. The objective of the present work was to estimate the risk of loss of biocontrol efficacy towards Botrytis cinerea, by evaluating the sensibility of various isolates of the pathogen to the biocontrol agent Microdochium dimerum. The protective efficacy of M. dimerum was evaluated on tomato plants against 41 strains of B. cinerea differing in their geographic origin and host of isolation. To this end, whole tomato pruning wounds and detached stem sections were concomitantly inoculated with B. cinerea and with M. dimerum. Lesion expansion was recorded daily from the 3rd to the 7th day after inoculation. Due to the very high level of efficacy against all tested strains of B. cinerea when M. dimerum was used at the recommended dose, it was necessary to reduce the dose of application 10-fold to assess the diversity of sensitivity of B. cinerea to this BCA. In these conditions, a wide range of sensitivities were observed among strains of the pathogen tested with protection levels ranging from 0 to 100% (mean = 53 ± 4%; median = 49%). A correlation was observed between the level of aggressiveness of a strain to tomato and its sensitivity to the biocontrol agent (assessed by the protection level). It reveals the importance of considering several strains of the pathogen when screening for biocontrol agents, to obtain a good representation of the pathogen population and thus take into account the potential durability of biocontrol.

chapitre 3; National audience

International audience; Genetic resistance provides efficient control of crop diseases but is limited by pathogen counteradaptation. The durability of the pvr23 allele, conferring resistance to Potato virus Y (PVY), was demonstrated to depend on the plant genetic background. In order to identify genetic factors affecting the durability of the pvr23 resistance, QTL mapping was performed using doubled-haploid (DH) lines issued from the F1 between two Capsicum annuum lines: ‘Perennial’ carrying pvr23 in a partially resistant background and ‘Yolo Wonder’ carrying the susceptible pvr2+ allele in a susceptible background. 350 DH lines were genotyped with 234 markers and the linkage map was established. The 156 DH lines carrying the pvr23 allele but segregating for the genetic background were evaluated for two traits: the breakdown frequency of pvr23 (following inoculation with a PVY clone nonpathogenic (avirulent) towards pvr23) and the PVY accumulation (following inoculation with a mutant of the previous PVY clone carrying a single mutation conferring pathogenicity towards pvr23). Genotypic variance was highly significant for the two traits with heritabilities of 0.76 and 0.47. One major QTL, explaining 29% of the variance of pvr23 breakdown frequency was identified on chromosome 3 and two QTLs, explaining 25% and 9% of PVY accumulation variation, were identified on chromosomes 3 and 6, respectively. Interestingly, the major QTL for the 2 traits mapped to the same region of chromosome 3. A putative pleiotropic effect affecting simultaneously the two traits, the underlying mechanism and the perspective in breeding for resistance durability will be discussed.

International audience; Pepper is known to be a recalcitrant species to genetic transformation via Agrobacterium tumefaciens. A. rhizogenes-mediated transformation offers an alternative and rapid possibility to study gene functions in roots. In our study, we developed a new and efficient system for A. rhizogenes transformation of the cultivated species Capsicum annuum. Hypocotyls and foliar organs (true leaves and cotyledons) of Yolo Wonder (YW) and Criollo de Morelos 334 (CM334) pepper cultivars were inoculated with the two constructs pBIN-gus and pHKN29-gfp of A. rhizogenes strain A4RS. Foliar explants of both pepper genotypes infected by A4RS-pBIN-gus or A4RS-pHKN29-gfp produced transformed roots. Optimal results were obtained using the combination of the foliar explants with A4RS-pHKN29-gfp. 20.5% of YW foliar explants and 14.6% of CM334 foliar explants inoculated with A4RS-pHKN29-gfp produced at least one root expressing uniform green fluorescent protein. We confirmed by polymerase chain reaction the presence of the rolB and gfp genes in the co-transformed roots ensuring that they integrated both the T-DNA from the Ri plasmid and the reporter gene. We also demonstrated that co-transformed roots of YW and CM334 displayed the same resistance response to Phytophthora capsici than the corresponding untransformed roots. Our novel procedure to produce C. annuum hairy roots will thus support the functional analysis of potential resistance genes involved in pepper P. capsici interaction. Keywords Capsicum annuum Á Agrobacterium rhizogenes Á Transformation efficiency Á Green fluorescent protein (GFP) Á b-Glucuronidase (GUS) Á Phytophthora capsici

International audience; Development of molecular markers has allowed the characterization of several host–aphid interactions. We investigated the usefulness of microsatellite markers to characterize the plant resistance interaction in the model Aphis gossypii/Cucumis melo. Six aphid clones, collected in different localities and years and belonging to two multilocus genotypes (MLGs) based on eight microsatellite markers, were phenotyped on a set of 33 melon accessions, some of them known to carry the Vat gene. Three parameters were used: acceptance of plant, ability to colonize the plant and resistance to virus when inoculated by aphids. Concordance and correlation analyses showed that aphid clones sharing a same MLG exhibited a very agreeable phenotype on the set of accessions for acceptance of plant and resistance to virus when inoculated by aphids. From host point of view, melon accessions were grouped into four clear categories, resistant to aphids of both MLGs, only resistant to the NM1 MLG, only resistant to the C9 MLG, susceptible to both MLGs and another group of unclear characteristics. The four categories revealed different patterns of virulence for NM1 and C9 MLGs that are likely controlled by a single avirulence gene in accordance with a gene for gene interaction. In contrast, the ability to colonize the plant appeared slightly variable among clones sharing a same MLG. We hypothesize it is due to the putative polygenic control of this aphid trait. Because the phenotypic variability of A. gossypii matched the genetic variability revealed by eight microsatellite markers, these markers could be used to infer the frequency of biotypes in field experiments and help to elucidate the allele diversity of melon resistance genes