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How do consumers choose to throw away food from a refrigerator? An observational study in controlled conditions. 7. European Conference on Sensory and Consumer Research (Eurosense).

Les sucres des plantes (glucose, fructose, saccharose, raffinose …) jouent un rôle fondamental dans la résistance de la plante à différents stress. On parle d’un nouveau concept de Sweet Immunity ou défense liée aux sucres. Le projet USAGE (2012-2014, ONEMA) a proposé de tester des applications foliaires d’infra-doses de sucres sur les plantes pour renforcer et accélérer le processus de Sweet Immunity sur différents couples de plante-bioagresseur. Le projet a regroupé 43 séries d’essais (6 en arboriculture, 12 en viticulture, 25 maraichage) dont 38 en conditions de productions. L’objectif générique était d’associer des sucres avec des doses réduites d’intrants tout en conservant la qualité de production agronomique. Les résultats, malgré les aléas d’expérimentations, ont permis d’observer un intérêt des applications de solutions de saccharose et de fructose pour le contrôle de différents bioagresseurs, lors de pressions parasitaires faibles à modérées et sur des cultures pérennes (vigne, arboriculture). Ainsi, les dégâts de carpocapse ont été réduits de 55% en arboriculture biologique avec le saccharose et le fructose. Dans les vignobles biologiques, les solutions de fructose ont permis de réduire les doses de cuivre contre le mildiou. Les résultats ont contribué à l’approbation du saccharose en substance de base (règlement d’exécution UE n° 916/2014 de la commission du 24 aout 2014)., Increasing interest is devoted to relationships between sugars (glucose, sucrose, fructose, raffinose…) and resistance of plants to biotic and abiotic stresses, resulting in the concept of “sweet immunity” or “sugar–enhanced defense”. The objective of the project USAGE (2012-2014) was to test the effect of spraying low doses of sugars on plants to control various bioagressors.The project brought together 43 trials (6 in orchards, 12 in vineyards, 25 with various vegetable crops) including 38 in field conditions. An additional objective was to evaluate the possibility to combine foliar application of sugars with reduced doses of pesticides while maintaining the quality of agricultural production. Some potential of sucrose and fructose was observed for the control of various parasites, at low to moderate pest pressures and I. Arnault et al. 2 Innovations Agronomiques 46 (2015), 1-10 on perennial crops (vineyards, arboriculture). Thus, the codling moth damage was reduced by 55% in organic orchards with both sucrose and fructose. Fructose sprays have reduced the amount of copperbased treatments used to control downy mildew in organic vineyards. The results contributed to the approval of sucrose as a basic substance (EU Regulations No. 916/2014 of the Committee on 24 August 2014).

19 pages; International audience; Since the beginning of the last century, the number of biological invasions has continuously increased worldwide. Due to their environmental and economical consequences, invasive species are now a major concern. Social wasps are particularly efficient invaders because of their distinctive biology and behavior. Among them, the yellow-legged hornet, Vespa velutina, is a keen hunter of domestic honeybees. Its recent introduction to Europe may induce important beekeeping, pollination, and biodiversity problems. Hornets use olfactory cues for the long-range detection of food sources, in this case the location of honeybee colonies, but the exact nature of these cues remains unknown. Here, we studied the orientation behavior of V. velutina workers towards a range of hive products and protein sources, as well as towards prominent chemical substances emitted by these food sources. In a multiple choice test performed under controlled laboratory conditions, we found that hornets are strongly attracted to the odor of some hive products, especially pollen and honey. When testing specific compounds, the honeybee aggregation pheromone, geraniol, proved highly attractive. Pheromones produced by honeybee larvae or by the queen were also of interest to hornet workers, albeit to a lesser extent. Our results indicate that V. velutina workers are selectively attracted towards olfactory cues from hives (stored food, brood, and queen), which may signal a high prey density. This study opens new perspectives for understanding hornets' hunting behavior and paves the way for developing efficient trapping strategies against this invasive species.

Most plant species selected as appropriate candidates for phytoextraction have been studied as monocultures. However, alternative cropping patterns which include rhizosphere microbial communities can significantly influence the extraction of metals, as well as soil protection and quality. Therefore, the objective of this work was to study the effect of species-rich vegetation cover, which consisted of three hyperaccumulator plant species, on the efficiency of nickel extraction from a naturally mineralized ultramafic soil. An experiment was set up with three hyperaccumulator species (Leptoplax emarginata, Noccaea tymphaea and Alyssum murale). Plants were cultivated separately (monospecific cover), or in combination (multispecies cover) in mesocosms under controlled conditions, on a nickel-rich ultramafic soil. Plants were grown for 92 days in controlled conditions. Each plant produced more biomass when grown in multispecies cover than alone. Noccaea and Alyssum showed the highest shoot Ni concentrations but Alyssum had by far the lowest shoot biomass. So, in this soil, Noccaea and Leptoplax have greater potential for hyperaccumulation than Alyssum. The amount of nickel accumulated in total biomass of Noccaea alone and of the multispecies cover was higher than that accumulated in either the monospecies Leptoplaxor Alyssum. Furthermore, the highest values of microbial biomass were obtained with the multispecies cover and a consistent production of auxin compounds by bacterial communities was measured, which emphasized the role of rhizosphere bacteria. The bacterial genetic structure also depended on the plant covers. A combination of the three species (multispecies cover), could be a good strategy for phytoremediation.

Various biological methods, mainly based on the utilization of antagonistic microorganisms or plant extracts, have been studied to control powdery mildews. The hyperparasite fungus Ampelomyces quisqualis (AQ-10, De Sangosse) is registered in many countries to control powdery mildew on various crops, including Oidium neolycopersici on tomato in France. A plant extract from orange (Prev-Am, Vivagro) is registered to control powdery mildew and whitefly on various crops but its effect on tomato powdery mildew is not clearly established. Spray of soluble carbohydrates on leaves of various plant species proved to have an effect against sorne plant pests but their effect against plant pathogens is not well known, except for trehalose against powdery mildew of wheat. The objectives of this study were (i) to test the effect of spraying low concentration of sugars (glucose, fructose, sucrose, trehalose) on leaves of tomato against O. neolycopersici in controlled conditions and (2) to evaluate the effect of sucrose, AQ-10 and Prev-Am separately and in combinations in semi­ commercial tunnel conditions. Results revealed that spray of sugars on tomato leaves have no significant effect against powdery mildew in controlled conditions. In tunnels, the plant extract Prev-am showed a significant effect against Oidium neolycopersici on tomato. Combination of products did not enhance the efficacy of a single product. The relevance of these results to ensure the control of powdery mildew on tomato without fungicides will be discussed.

The preventive use of resistance inducers has been shown to be an interesting method to reduce dependency on pesticides for plant protection. However, little is known on possible differences in the protective effects of such methods for different varieties of a given crop. In the present study, we assessed the effect of three compounds (acibenzolar-S-méthyl, a calcium-based mineral compound and a yeast extract) for the protection of six varieties of lettuce against two major pathogens, Sclerotinia sclerotiorum and Botrytis cinerea. The compounds were sprayed on the plants three days before inoculation. A water spray was used as a control. The protective effect of the compounds was then assessed by comparing the size of lesions developing on inoculated leaves. For both pathogens, none of the compounds fully inhibited disease development. However, reduction in lesion size was observed on some of the leaves. The effect of the three compounds was different for the two pathogens. For tests with B. cinerea, effects of plant treatment were not statistically significant. In contrast, significant effects were found for five of the varieties inoculated with S. sclerotiorum. Overall, the yeast extract provided the highest level of protection against that pathogen. However, for all compounds, the extent of the protective effect depended on the variety. Furthermore, in some cases the effect of the compound was opposite to that desired and disease was more severe on treated plants than on the water control. Possible consequences for field application of such methods will be discussed.

L’incidence des mycoses à Beauveria bassiana (Bals.-Criv) Vuillemin comme rôle régulateur de la dynamique de la processionnaire du pin (Thaumetopoea pityocampa Denis & Schiff.) est connue depuis les années 1950. La mortalité par mycose intervient essentiellement au stade nymphal. La présente étude a été conduite en condition contrôlée afin d’évaluer l’efficacité de Beauveria bassiana souche 147 (Bb147) sur la contamination de chenilles processionnaires du pin lors de l’enfouissement pour la nymphose. Les résultats ouvrent une perspective d’utilisation de ce champignon entomopathogène en pépinière. Il pourrait être utilisé comme agent de biocontrôle pour les plants en conteneur. Ce traitement apporterait une assurance sanitaire pour le substrat en limitant la présence de processionnaires du pin. Il serait un outil indispensable pour le transport de pins ou cèdres hors de l’aire de distribution de la processionnaire du pin afin d’éviter son extension et donc les risques sanitaires., The incidence of Beauveria bassiana (Bals.-Criv) Vuillemin fungal infections as regulatory role of the dynamics of the pine processionary moth (Thaumetopoea pityocampa Denis & Schiff.) has been known since the 1970s. Fungal mortality occurs mainly in the pupal stage. This study was carried out under controlled conditions to evaluate the efficacy of Beauveria bassiana strain 147 (Bb147) on the contamination of the pine processionary larvae during the burying for pupation.The results open the prospect of using this entomopathogenic fungus in nursery. It could be used as a biocontrol agent for plants in containers. This treatment would provide health guarantee for the substrate limiting pine processionary presence. It would be a necessary tool for the transport of pines or cedars outside the distribution area of the pine processionary to prevent its extension and thus the health risks.

Dans le cadre de la promotion de systèmes de culture alternatifs à moindres intrants chimiques, des études sur l’introduction de plantes de service ayant vocation à réduire l’usage des pesticides et engrais azotés mobilisent un effort de recherche considérable. Dans le cadre de la production bananière pour laquelle la nuisibilité causée par les nématodes phytoparasites constitue l’une des principales contraintes, une des principales alternatives à l’utilisation de nématicides chimiques repose sur l’usage raisonné en rotation ou en association culturale de plantes de service à propriétés nématorégulatrices. Parmi les espèces candidates, celles du genre Crotalaria spp. ont largement été étudiées en raison de leur aptitude à contrôler les nématodes phytoparasites. Une méta-analyse révèle cependant que même si de nombreux auteurs s’accordent à reconnaître les propriétés allélopathiques des plantes de cette espèce, ils sont également enclins à reconnaître la forte variabilité d’expression de ces propriétés vis-àvis du contrôle des nématodes selon les situations expérimentées. L’objectif de ce travail repose sur la compréhension du déterminisme biochimique des exsudats.[br/] La stratégie expérimentale mise en oeuvre a consisté à tester en conditions contrôlées le comportement biochimique des exsudats racinaires de deux espèces de crotalaires (C. retusa, C. spectabilis) et d’une espèce sensible, le bananier dessert (Musa spp.) en fonction i) de conditions biotiques variées - i.e. présence ou non de nématodes (Radopholus similis et Meloidogyne arenaria), et présence ou non de mycorhizes-, ii) de conditions abiotiques contrastées – i.e. utilisation d’un sol naturel vs. substrat neutre, ajout ou non d’engrais chimique. La méthodologie innovante des « plantes à traire » (Brevet INRA) a été requise pour pouvoir travailler sur les exsudats racinaires des plantes conditionnées plutôt que sur des lixiviats, comme réalisé dans des expérimentations antérieures. [br/] Les résultats obtenus en spectrophométrie visible montrent que la présence ou l’absence de nématodes affecte de manière importante les profils biochimiques des plantes étudiées. En présence du nématode M. arenaria les profils biochimiques des deux crotalaires sont également modifiés. Des biotests réalisés à l’aide des exsudats racinaires conditionnés au préalable par les modifications biotiques ont permis de démontrer l’effet nématostatique des crotalaires. Des analyses biochimiques en GC-MS mettent en évidence de manière plus précise des molécules actives mises en jeu sous différentes modalités biotiques et abiotiques. [br/] Ces recherches, de portée générique, permettront de mieux comprendre les conditions de l’environnement qui régulent les profils biochimiques des exsudats racinaires des crotalaires et par extension, seront applicables aux recherches menées sur d’autres plantes de service candidates. Ceci aidera, à terme, à définir les conditions environnementales à réunir, pour orienter de manière optimale les effets allélopathiques dans une perspective de nématorégulation naturelle., As part of the promotion of alternative cropping systems at lower chemical inputs, studies on the introduction of cover crops designed to reduce the use of pesticides and nitrogen fertilizers mobilize a considerable research effort. Under banana production for which the harmfulness caused by plant-parasitic-nematodes is one of the main constraints, one of the main alternatives to the use of chemical nematicides is based on the rational use in rotation or intercropping of cover crops to protect crops from plant-parasitic-nematodes. [br/] Among the candidate species, the species from the genus of Crotalaria spp. have been widely studied because of their ability to control plant parasitic-nematodes. A meta-analysis reveals that although many authors agree allelopathic properties of these species, they are also likely to recognize the high variability of expression of these properties vis-à-vis the control of nematodes according to the situations experienced. The objective of this work is focused on the understanding of the biochemical determinism of root exudates under environment biotic and abiotic variations. [br/] The experimental strategy was to test under controlled conditions the biochemical behavior of root exudates of two species of crotalarias (C. retusa, C. spectabilis) and a susceptible species, the dessert banana crop (Musa spp.) with i) modification of biotic conditions - ie presence or absence of nematodes (Meloidogyne arenaria and Radopholus similis), and presence or absence of mycorrhiza- ii) contrasting abiotic conditions - ie using a natural soil vs. neutral substrate, whether to add fertilizer. The innovative methodology of "milking plants" (Patent INRA) was required in order to work on the root exudates of plants packed rather than leachate, as done in previous experiments.[br/] The results obtained in visible spectrophotometry show that the presence or absence of nematodes affect significantly the biochemical profiles of the studied plants. In the presence of nematode M. arenaria biochemical profiles of both crotalarias are also changed. Bioassays conducted using root exudates conditioned in advance by biotic changes have demonstrated the effect of nématostatique crotalarias. Biochemical GC-MS demonstrate more clearly active molecules that are involved in various biotic and abiotic conditions. [br/] This research, generic scope, to better understand the environmental conditions that regulate biochemical profiles of root exudates crotalarias and by extension, will apply to research on other plants service candidates. This will ultimately define the environmental conditions to meet, to guide optimal allelopathic effects from the perspective of natural nématorégulation.

This deliverable D3.2 (Site preparation) is linked to the first task (3.1) of DIGISOIL’s WP3 (Implementation, field testing and validation on selected test sites). The objectives are here to report all the experiments that have been conducted on real test sites to evaluate the proposed methodology. Test sites are identified as Luxembourg (LU), Mugello (IT) and Zala (HU). For each geophysical method, the experimental conditions, data acquisitions, validation points and produced maps are presented. The optimal combination of petrophysical parameters are used to describe the aforementioned soil properties. The inference functions and fusion techniques developed in WP 2 are applied to the field conditions of the different test sites. Where possible geo-referenced data sets and maps were used for calibration and validation of the geophysical techniques. In some cases, additional analyses can be required to fill the gaps in the datasets and cover the selected dynamic soil properties. The experimental conditions, the results and the costs of the experiments and measurements for each geophysical method (Hyperspectral, GPR, EMI, Geoelectric, Seismic), in terms of man-day, are reported. After a general introduction that indicates the specific content of this deliverable in relationship with the deliverables of WP2 and other deliverables of WP3, each experiment is described in detail. The plan is organized by experimentations but several geophysical methods may have been run at the same site.

This deliverable is linked to the second task (2.2) of DIGISOIL's WP2 "Laboratory or field calibration in controlled conditions". The objective here are to report all the experiments that have been conducted under controlled conditions, either in the laboratory, or in the field, both at the calibrating sites Beauce (France), Roujan (France) or Telega (Romania), or in any other field site that has been thought to conditions, the experimental results and the costs of the experiments in terms of man-day are reported. After a general introduction that indicates the specific content of this deliverable in relationship with the deliverables of WP1 and other deliverables of WP2, each experiment is described in detail. The plan is organized by geophysical tool but several geophysical methods may have been run at the same site. The reader is suggested to refer to Table 9 for synthesis.

A B S T R A C T Mineralization is the main mechanism of dissipation of glyphosate herbicide (N-[phosphonomethyl] glycine) in soil. However, there is scarce information about the mineralization process in strata formed by stubbles in no-tillage systems. The kinetics and rate of mineralization of herbicide in stubbles of soybean (Glycine max L. Merr.) and corn (Zea mays L.) were investigated. To evaluate the effect of age of crop residues, samples of soybean stubbles were collected immediately after harvest (Soja 1) and four months after harvest (Soja 2). Corn crop residues were collected three months after harvest. Glyphosate evolution and total microbial activity (TMA) were monitored by release of 14 C-CO2 and C-CO2 under laboratory conditions with two temperatures, 15 and 28 oC. Crop residues size was evaluated using grinding (1 mm) and cut (1 to 2 cm) stubbles. Results showed that glyphosate mineralization was affected by the incubation temperature and the origin and age of crop residues. Size of crop residues did not modify glyphosate mineralization. Average glyphosate mineralization after 56 days of incubation at 15 and 28 oC was of 3.9 and 9.9%, respectively, of the 14 C-glyphosate initially applied. In corn crop residues the percentages were 2.0 and 3.0%, respectively, at 15 and 28 oC. A similar evolution was detected for TMA. The co-metabolic nature of glyphosate mineralization was corroborated. An inverse relation between C/N ratio and glyphosate mineralization was detected. Higher glyphosate mineralization was detected in fresh soybean stubbles, suggesting that applications on aged crop residues could increase the persistence of glyphosate in notillage systems.

Des insecticides organochlorés (dieldrine, HCH, chlordécone) ont été appliqués dans les bananeraies des Antilles françaises des années 60 à 90. Les deux premiers sont rarement détectés dans les sols et les eaux. La chlordécone, très stable et hydrophobe, a été largement détectée depuis 1999 dans les eaux de source, puis dans les «racines» récoltées. L’analyse des sols de parcelles agricoles renseignées par des chroniques rétrospectives d’apports a permis de valider un modèle de dissipation de la chlordécone par les eaux de drainage, seul processus permettant la très lente décontamination des sols. Les coefficients de partage apparents, élevés, entre la fraction sorbée sur la matière organique des sols et la fraction en solution (Koc), décroissent selon la nature minéralogique des sols : allophane, halloysite + oxyhydroxides, halloysite. Les concentrations des eaux de drainage confirment la réalité des différents Koc. Des expérimentations au champ et en conditions contrôlées ont montré la prédominance d’une contamination des organes végétaux souterrains par contact, compliquée par une distribution de la chlordécone en «copeaux» dans les sols. Là où la chlordécone n’a pas été profondément incorporée par des labours, des décapages superficiels localisés en créneaux permettent d’obtenir des «racines» peu contaminées. Aucun indice de biodégradation ni solution de bio-remédiation n’ont été identifiés., Between the 60’ and the 90’, organochlorides, i.e. dieldrin, HCH and chlordécone have been applied as insecticides on banana crops in the F.W.I.. The firsts are rarely detected in water resources. Since 1999, chlordecone has been largely detected in sparkling waters, and then in harvested roots (yam, sweet potato, dasheen…). Soil analysis of a “space for time” parcel network, where different chlordecone input schedules have been established, allowed validating a model of chlordecone dissipation by drainage water. This process appeared to be the only one capable of reducing the soil contamination. The bulk partition coefficients between the sorbed fraction on the soil organic matter and the soluble fraction (Koc) decreased according to the nature of the mineral fraction: allophane, halloysite +oxi-hydroxides, halloysite. The drainage water concentrations corroborated this gradation. Field and green-house experiments showed that the contamination of below ground plant organs results mainly from a contact with the surrounding soil, which was difficult to highlight because of the chip distribution of chlordécone. Where chlordecone has not been deeply incorporated by previous tillage, local scrapings allow to harvest few contaminated “roots”. No biodegradation index or bio- remediation plant has been identified.

1. The proximate behavioural rules adopted by parasitoid females to manage their foraging time on patches of hosts were studied, under standardized laboratory conditions, in different species (and populations) of the Trichogrammatidae (Hymenoptera) family. 2. Seventeen species/populations were compared and the behavioural mechanisms adopted by the females were identified by means of a Cox's proportional hazards model. 3. On average, females increased their patch-leaving tendency each time a healthy host was attacked and each time a parasitized host was rejected. 4. Strong variation was observed in these patch-leaving mechanisms among the different species. 5. Moreover, the interspecific variation in these two behavioural mechanisms showed a significant positive correlation, and this correlation remained significant when the phylogenetic relationship between the strains was controlled with the use of phylogenetic comparative methods. 6. The adaptive and evolutionary meanings of these results are probably related to the ecological features and distribution patterns of the hosts attacked by the species/populations compared.

International audience; Ectomycorrhization of Cedrus atlantica seedlings under controlled conditions: Efficiency of two forms of mycelial inocula. The effect of two mycelial inocula (mycelia grown in peat-vermiculite saturated by a nutritive medium, or entrapped into alginate) of two ectomycorrhizal species (Tricholoma tridentinum var. cedretorum and Hebeloma sinapizans) was tested, under controlled conditions, on the mycorrhization of Cedar seedlings grown on mineral substrate. One year after inoculation, the percentage of infected root tips and root ergosterol contents were higher with cedars inoculated using T. tridentinum peat-vermiculite inoculum than using alginate one. The opposite results were obtained with H. sinapizans. The degrees of mycorrhization of the seedlings inoculated with T. tridentinum were higher than those of the seedlings inoculated with H. sinapizans. The mycorrhization of Cedrus atlantica seedlings using mycelial inocula was thus performed under controlled conditions which may be reproducible. The consequences of the inoculation of seedlings on their shoot and/or root biomass vary with the inoculum form and fungal species.; L'effet de la forme de l'inoculum (obtenu sur tourbe-vermiculite ou par inclusion dans l'alginate) de Tricholoma tridentinum var. cedretorum et Hebeloma sinapizans sur la mycorhization de semis du Cèdre de l'Atlas, cultivés sur un substrat minéral, a été expérimenté en conditions contrôlées. L'utilisation de mycélium de T. tridentinum développé sur tourbe-vermiculite permet d'obtenir des degrés de mycorhization supérieurs à ceux enregistrés en employant du mycélium du même champignon inclus dans l'alginate, un an après l'inoculation. Le résultat inverse a été obtenu avec H. sinapizans. Les pourcentages d'apex mycorhizés et les teneurs en mycélium viable des racines des plants inoculés par T. tridentinum ont été supérieurs à ceux des plants inoculés avec H. sinapizans. L'obtention de mycorhizes à l'aide d'inocula mycéliens, a été réalisée sur le Cèdre de l'Atlas dans des conditions contrôlées et reproductibles. L'inoculation des semis par du mycélium d'H. sinapizans cultivé sur substrat solide a stimulé la biomasse de leurs parties aériennes et racinaires alors que l'inoculum de T. tridentinum, produit sur le même substrat, n'a permis d'augmenter significativement que la biomasse des racines. L'inoculation des plants par du mycélium d'H. sinapizans inclus dans l'alginate n'a été bénéfique que pour la biomasse de leurs parties aériennes.

Susceptibility of various Tomato and Lettuce genotypes to plant-growth-promoting [i]Pseudomonas[/i]

Une double expérimentation en conditions naturelles et en conditions contrôlées est conduite afin de déterminer la validité de certains critères de résistance à l’hiver. La capacité de développer des rameaux secondaires au cours de l’endurcissement et lors de la reprise de végétation déterminée en conditions contrôlées peut être retenue. Complémentairement, la teneur en eau des parties aériennes avant tout traitement thermique est un bon indicateur. L’étude de l’évolution des teneurs en métabolites caractéristiques (sucres totaux solubles, saccharose et proline solubles) ne fournit pas de critères suffisamment discriminants pour le lin., Simultaneous experiments were conducted under natural and controlled conditions in order to determine the validity of some frost resistance criteria given in the literature. The ability of plants to develop secondary axes, or "tillering" ability, during hardening and chilling recovery (table 3 and fig. 2a), as well as the water content of aerial parts before temperature treatments (fig. 2c) could be good indices. These parameters, which are affected by environmental factors, must be determined under standardized conditions. The free proline, free sucrose and free total sugar contents could not be considered for flax, although their changes in value during temperature treatments gave some comparative elements.

Vingt et un isolats de Sclerotinia trifoliorum Eriks. de trèfle violet (Trifolium pratense L.), trèfle incarnat (T. incarnatum L.) et luzerne (Medicago sativa L.) ont été examinés pour la variabilité de leurs caractères culturaux et, au moyen de contaminations artificielles, de leur pouvoir pathogène. De nombreux variants apparaissent spontanément dans les cultures pures. Ils diffèrent par le nombre et la taille des sclérotes, l’aspect et la couleur du mycélium ; certains produisent la forme microconidienne Myrioconium. Bien qu’il soit impossible dans la plupart des cas de relier le pouvoir pathogène aux caractères culturaux, 2 isolats à croissance lente et ne produisant pas de sclérotes se sont avérés dépourvus d’agressivité sur trèfle violet. Le pouvoir pathogène des isolats, testé sur 2 cultivars de trèfle violet, montre une variabilité importante, la plupart étant toutefois moyennement agressifs dans nos conditions expérimentales. Il n’existe aucune interaction isolat x cultivar. Les niveaux de résistance de 13 cultivars de trèfle violet et de 12 cultivars de luzerne ont été évalués avec un isolat de S. trifoliorum, sur des plantes âgées de 2 mois. Le trèfle violet est globalement plus sensible que la luzerne. Les cultivars tétraploïdes de trèfle violet sont plus résistants que les diploïdes. Les cultivars de luzerne montrent en général de bons niveaux de résistance. Parmi les trèfles et luzernes sauvages testés, certains possèdent de très hauts niveaux de résistance. Medicago rugosa Desr. et M. scutellata (L.) Mill. sont totalement immunes dans nos conditions. Trifolium fragiferum L. et T. isthmocarpum Brot. sont très résistants. S. minor Jagg. et S. sclerotiorum (Lib.) de By. se sont montrés dénués d’agressivité sur trèfle violet., Twenty one isolates of Sclerotinia trifoliorum Eriks. from red clover (Trifolium pratense L.), crimson clover (T. incarnatum L.) and alfalfa (Medicago sativa L.), have been tested for the variability of their cultural characters and, by artificial inoculation, for their pathogenicity. Spontaneous variants appeared in great number in pure cultures. They differed in sclerotial characteristics (number and size) and mycelial characteristics. Some exhibited the microconidial Myrioconium form. Although it was impossible in almost all cases to correlate pathogenicity and cultural behaviour, 2 slow-growing isolates without sclerotia showed no aggressiveness on red clover. The pathogenicity of isolates, tested on 2 cultivars of red clover showed a significant variation. However, many isolates were fairly aggressive in our experimental conditions. No cultivar x isolate correlation was evident. The resistance levels of 13 red clover and 12 alfalfa cultivars were evaluated with 1 isolate of S. trifoliorum on 2 months old plants. Red clover was more susceptible than alfalfa. Tetraploid cultivars of red clover were more resistant than diploids. In general, the alfalfa cultivars showed good levels of resistance. Among wild clovers and alfalfas, some showed very high levels of resistance. Medicago rugosa Desr. and M. scutellata (L.) Mill. were completely immune. Trifolium fragiferum L. and T. isthmocarpum Brot. were very resistant. S. minor Jagg. and S. sclerotiorum (Lib.) de By. were not aggressive on red clover.

Influence de la température appliquée pendant la germination de pépins de Poirier, [i]Pyrus communi[/i]s L. sur la croissance ultérieure des plants.

Cette étude en conditions contrôlées de la formation des apothécies par S. trifoliorum a pour but d’optimiser les conditions de production d’un inoculum ascosporé pour la sélection de trèfles résistants à la sclérotiniose. Le milieu de production in vitro des sclérotes agit sur la quantité et les dimensions des sclérotes et des apothécies. La taille des sclérotes influe sur la carpogenèse. La dormance des sclérotes peut être levée par dessication à 30 °C pendant une durée optimale d’un mois. Des sclérotes enfouis dans le sol, à l’extérieur, au printemps, sont aptes à produire des apothécies dès juillet s’ils sont placés en conditions favorables. Enfouis à plus de 2 cm, ils différencient des stipes ramifiés qui n’émergent pas du sol, mais sont aptes à produire des apothécies si on les place à la lumière. La lumière est indispensable à la carpogenèse. Plus l’énergie lumineuse reçue (de 20 à 800 μwcm-2) est forte, plus la différenciation des apothécies est rapide. La lumière blanche est plus favorable, les radiations bleues (475-500 nm) les moins favorables. L’obscurité continue empêche l’évolution des stipes. La différenciation des apothécies nécessite une forte humidité de l’atmosphère et une imbibition continue du substrat d’incubation des sclérotes. La perlite et le sable sont défavorables à la carpogenèse, contrairement à la vermiculite. Une terre de jardin s’est révélée très favorable, à l’inverse d’un sol limoneux. Enfin, tous les isolats de S. trifoliorum de trèfle et de luzerne ne sont pas également aptes à produire des apothécies., A study under controlled conditions on apothecium formation by S. trifoliorum aimed to find the best conditions for the production of ascospores to be used for selection of clovers resistant to crown rot. The culture medium for in vitro production of the sclerotia influenced quantity and dimensions of sclerotia and apothecia. The dimensions of sclerotia had an effect on carpogenesis. The dormancy of sclerotia was removed by drying at 30 °C for the optimal duration of 1 month. Sclerotia buried outdoors in the soil in spring were able to differentiate apothecia as early as July, when placed in favourable conditions. When the depth of burial exceeded 2 cm, sclerotia differentiated branched stipes which never emerged, but were able to produce apothecia when placed under light. Light was essential to carpogenesis. The higher the light energy (from 20 to 800 μwcm-2), the faster the differentiation of apothecia. White light was most effective, blue waves less. Continuous obscurity inhibited stipe evolution. Apothecium differentiation needed high atmospheric humidity and a damp substrate for the incubation of sclerotia and evolution of stipes. Perlite and sand were unfavourable to carpogenesis, unlike vermiculite. Garden soil was very conducive, but not a silt soil. The S. trifoliorum isolates from clover and lucerne were not all equally able to produce apothecia.

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*INRA, Centre de Recherches d'Avignon, URD, Domaine Saint Paul, BP 91, 84143 Montfavet cedex Diffusion du document : INRA, Centre de Recherches d'Avignon, URD, Domaine Saint Paul, BP 91, 84143 Montfavet cedex; National audience

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International audience; In addition to its environmental implications, ammonia volatilization is the principal source of variation of fertilizer efficiency. In a larger study estimating the effect of the dissolution step of fertilizer pellets on ammonia volatilization, we analyzed the sources of uncertainties in measuring low ammonia fluxes. The air humidity, and above all the air flow rate, are important contributors to the variation in fluxes. An exponential curve obtained from a set of 35 data points is proposed to normalize the ammonia emission rates according to the air flow rate (R2 = 0.52). Modifications of the standard laboratory method are also proposed to improve the estimation of the low ammonia fluxes over a short timescale. However, the system was kept simple to manage, and reproducible to perform a statistical analysis of the results.