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Focus sur la « viande in vitro » : est-il possible de nourrir l'humanité en cultivant des fibres musculaires ?
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Impacts of the Winter Pea Crop (Instead of Rapeseed) on Soil Microbial Communities, Nitrogen Balance and Wheat Yield
No full textInternational audienceDue to legume-based systems improving several aspects of soil fertility, the diversification of agrosystems using legumes in crop succession is gaining increasing interest. The benefits of legumes aroused the interest of farmers in the association of the Economic and Environmental Interest Group (EEIG), who introduced the idea of using the winter pea instead of rapeseed in their crop succession. The aim of this study is to evaluate the effects of the winter pea compared to those of rapeseed, as a head crop of the rotation, on soil microbial communities, enzyme activities, nitrogen (N) balance and yields. The field experiment involved two farmer plots that were selected within the EEIG. In each plot, two crop successions, including winter pea–wheat and rapeseed–wheat with fertilized and unfertilized strips, were examined for two years. Three times a year, under the wheat crop, composite soil samples were collected at depths of 0–20 cm, for microbial abundance and enzyme activity analyses, and twice a year at a depth of 0–60 cm, for the measuring of the mineral N. The results showed that the rapeseed–wheat succession maintained or enhanced soil bacterial and fungal biomasses and their enzyme activities. The winter pea–wheat succession enriched the soil’s mineral N content more consistently than the rapeseed–wheat succession. The mineral N enhancement’s effect was maintained under the wheat crop. Overall, the impact of the winter pea was positive on the soil’s N dynamics, but wheat yields were equivalent regardless of the previous crop (winter pea or rapeseed with and without fertilization). In the Normandy region, as rapeseed requires a large amount of N fertilizer and pesticide to maintain the yield and quality of crop products, it is suitable to favor the introduction of the winter pea as the head crop of the rotation, which indirectly allows for a reduction in the costs of input production and use, the working time of farmers and environmental pollutio
Deciphering the pluripotency continuum in vivo using the rabbit model
No full textInternational audiencePluripotency describes the ability of a stem cell to give rise to all cell types in mature organisms. Two main types of pluripotent stem cells (PSCs) have been described: naïve and primed. In rodents, naïve-state pluripotency characterises mouse embryonic stem cells (mESCs) that have been derived from the pre-implantation epiblast. In primates (human and monkey) and lagomorphs (rabbits), ESCs only exist in the primed state of pluripotency. Primed-state pluripotency characterises the epiblast of developmentally more advanced embryos, closer to the commitment to differentiation. Contrary to naïve PSCs, PSCs in the primed state of pluripotency fail to make chimeras when introduced into host blastocysts. Several methods have been developed to reprogram human and monkey ESCs to naïve-like pluripotency using various cocktails of growth factors and small molecules. However, none of them works in rabbits, suggesting that the molecular network of naïve pluripotency differ between primates and lagomorphs. This study aimed to decipher the molecular signature of naïve pluripotency in the rabbit. Using single-cell 10x Chromium RNA-sequencing of rabbit embryos, we analysed the expression of genes regulating pluripotency, as well as genes involved in other processes that shape pluripotency (cell-cycle machinery, chromatin-related regulators, metabolism). From those data, we observed strong similarities between rabbits, primates, and rodents. However, we also observed differences in the expression of well-known marker of naïve pluripotency in mice, such as Zinc-Finger Protein 42 (ZFP42, also known as REX1) or Teratocarcinoma-Derived Growth Factor 1 (TDGF1, also known as CRIPTO). We also identified novel molecular markers useful to characterize naïve-state pluripotency in rabbits that could then be used to capture naïve-state pluripotency in rabbit PSCs
Landscape diversity and field border density enhance carabid diversity in adjacent grasslands and cereal fields
No full textInternational audienceContext Permanent grasslands have declined across Europe since the agricultural intensification. Grassland vicinity, landscape heterogeneity and vicinity of hedgerows are enhancing factors for farmland carabid (ground beetle) diversity. However, interrelation between grassland and cropland communities needs to be better known in various landscape context. Objectives In this study we disentangle the effects of different landscape indicators carabid communities of adjacent grasslands and cereal fields to assess mutual benefits of these two land cover types. Methods We sampled carabids in three agricultural plains of southeastern France, each associated with a gradient in grassland coverage. We used regression models to point out effects of landscape indicators on the separate, overall and common carabid species richness of paired cereal crops and grasslands. Results Landscape Shannon diversity and field border density explained best gamma species richness. In grasslands, we found a higher species richness when the landscape diversity increased, except in the study region dominated by grasslands. In cereal crops, the landscape parameters showed no significant effect on carabid richness. Finally, the common species richness from cereal fields and grasslands was explained by higher density of field borders between them, but also by higher grassland coverage where grasslands were the scarcest. Conclusions Our results suggest that cropland carabid communities may benefit from the habitat and resource complementation provided by grasslands. This finding pleads for the preservation of grasslands in cropped landscapes to favor carabids and illustrates the potential for enhanced biological control in future cropping systems with reduced pesticide inputs
The myth of cultured meat: A review
No full textInternational audienceTo satisfy the increasing demand for food by the growing human population, cultured meat (also called in vitro, artificial or lab-grown meat) is presented by its advocates as a good alternative for consumers who want to be more responsible but do not wish to change their diet. This review aims to update the current knowledge on this subject by focusing on recent publications and issues not well described previously. The main conclusion is that no major advances were observed despite many new publications. Indeed, in terms of technical issues, research is still required to optimize cell culture methodology. It is also almost impossible to reproduce the diversity of meats derived from various species, breeds and cuts. Although these are not yet known, we speculated on the potential health benefits and drawbacks of cultured meat. Unlike conventional meat, cultured muscle cells may be safer, without any adjacent digestive organs. On the other hand, with this high level of cell multiplication, some dysregulation is likely as happens in cancer cells. Likewise, the control of its nutritional composition is still unclear, especially for micronutrients and iron. Regarding environmental issues, the potential advantages of cultured meat for greenhouse gas emissions are a matter of controversy, although less land will be used compared to livestock, ruminants in particular. However, more criteria need to be taken into account for a comparison with current meat production. Cultured meat will have to compete with other meat substitutes, especially plant-based alternatives. Consumer acceptance will be strongly influenced by many factors and consumers seem to dislike unnatural food. Ethically, cultured meat aims to use considerably fewer animals than conventional livestock farming. However, some animals will still have to be reared to harvest cells for the production of in vitro meat. Finally, we discussed in this review the nebulous status of cultured meat from a religious point of view. Indeed, religious authorities are still debating the question of whether in vitro meat is Kosher or Halal (e.g., compliant with Jewish or Islamic dietary laws)
Apoptosis, G1 phase stall and premature differentiation account for low chimeric competence of Human and rhesus monkey naïve pluripotent stem cells
No full textSummary After reprogramming to naïve pluripotency, human pluripotent stem cells (PSCs) still exhibit very low ability to make interspecies chimeras. Whether this is because they are inherently devoid of the attributes of chimeric competency or because naïve PSCs cannot colonize embryos from distant species remains to be elucidated. Here, we have used different types of mouse, human and rhesus monkey naïve PSCs and analyzed their ability to colonize rabbit and cynomolgus monkey embryos. Mouse embryonic stem cells (ESCs) remained mitotically active and efficiently colonized host embryos. In contrast, primate naïve PSCs colonized host embryos with much lower efficiency. Unlike mouse ESCs, they slowed DNA replication after dissociation and, after injection into host embryos, they stalled in the G1 phase and differentiated prematurely, regardless of host species. We conclude that human and non-human primate naïve PSCs do not efficiently make chimeras because they are inherently unfit to remain mitotically active during colonization
Semis direct sous couvert végétal sans herbicide : conception, expérimentation et évaluation conjointes d’itinéraires techniques entre praticiens et chercheurs
No full textCover crop-based no-tillage (NT) techniques appear as an innovative solution to manage weeds while limiting soil disturbance and facing economic, sociologic and agro ecologic challenges of the 21st century (Mäeder et Berner, 2012). This technic consists of sowing a cash crop without tillage either under living or terminated cover crop with a roller crimper (Mirsky et al., 2012). This innovation has been developed in North America and NT is emerging in France. Especially, farmers are motivated by NT adoption to improve soil fertility, reduce fuel and herbicides consumption and decrease labor (Soane et al., 2012 ; Casagrande et al., 2015). Cover crop-based NT practice represents a major challenge both in organic farming and conventional farming to reduce tillage and limit and/or replace the use of the Glyphosate causing discussions in Europe (Johnsen et al., 2016). However, high number of difficulties are often reported (cover crop control, weeds management, nitrogen availability etc.) and a system rethinking is required to limit them. In addition, only few references are available on this subject and most of the studies have been conducted in North America (Moyer, 2011). Consequently, concerns reminds on means to adopt the innovation in current farms (equipment, skills, knowledge, technical and organizational choices etc.) and on economic and agronomic benefits provided by cover crop-based NT techniques. This thesis relies on these three major issues and proposes to design viable solutions in current farms integrating cover crop-based NT techniques under European conditions. This thesis project aims especially to consider the farmer’s objectives and constraints at three organizational level (plot, cropping systems, farm) combining both a systemic and an analytic approach.Le semis direct sous couvert végétal (SDSC) apparaît comme une solution innovante pour gérer les adventices tout en limitant les dégradations des sols et en répondant aux enjeux économiques, sociologiques et agroécologiques du XXIème siècle (Mäeder et Berner, 2012). Cette technique culturale sans labour consiste à implanter une culture, sans travail du sol, soit sous un couvert végétal vivant soit sous un couvert détruit mécaniquement à partir d’un rouleau cranteur (Mirsky et al., 2012). Cette innovation se développe en Amérique du Nord et commence à émerger en France. Elle suscite en effet beaucoup d’intérêts auprès des agriculteurs qui souhaitent améliorer la fertilité des sols, réduire la consommation de carburant et d’herbicides ou encore limiter le temps de travail (Soane et al., 2012 ; Casagrande et al., 2015). Cette technique constitue un enjeu majeur à la fois en agriculture biologique et en agriculture conventionnelle pour diminuer le recours au travail du sol et limiter ou remplacer l’utilisation du glyphosate à l’origine de nombreux débats en Europe (Johnsen et al., 2016). Toutefois, d’importantes difficultés sont souvent relevées lors de l’adoption du SDSC (maîtrise du couvert et des adventices, disponibilité de l’azote etc.) et une reconsidération de l’ensemble du système serait nécessaire pour les limiter. De plus, peu de références existent sur cette thématique et la majorité des études a été menée dans un contexte nord-américain (Moyer, 2011). Ainsi, des questions persistent sur les moyens de mise en œuvre de cette innovation dans les exploitations agricoles actuelles (machinisme, compétences, connaissances, choix techniques et organisationnels etc.) ainsi que sur les performances économiques et agronomiques du SDSC. Cette thèse s’axe donc autour de ces trois grandes problématiques et propose de développer des solutions viables chez les agriculteurs pour intégrer cette technique dans un contexte européen. Ce projet vise notamment à prendre en compte les objectifs et les contraintes des producteurs à plusieurs niveaux d’organisation (parcelle, systèmes de culture, exploitation agricole) en alliant une approche à la fois systémique et analytique
Influence du paysage et de la parcelle sur les diversités de carabes et d’autres arthropodes en céréales et prairies permanentes
No full textBiodiversity is decreasing dramatically worldwide with land use change and habitat degradation being among its major causes. In Europe, this biodiversity loss is strongly related to the intensification of agriculture which has led to the simplification of landscapes. This resulted in the homogenization of landscapes where only a few crops dominate, accompanied with an increase of field size. Natural and semi-natural landscape elements, such as hedgerows, vegetation strips and groves were withdrawn, while more and more grasslands were being cropped or abandoned. Yet, grasslands are important functional biodiversity providers for crops in agricultural landscapes, including species that can provide ecosystem services such as pest control or pollination to farming activities. This PhD thesis therefore aimed at disentangling the influence of field and landscape parameters on the arthropod communities of adjacent grasslands and croplands of agricultural landscapes.We sampled arthropods from pairs of neighboring cereal fields and grasslands in order to compare the field and landscape influences on the biodiversity of these two agricultural land cover types. Our research took place in three study regions of southeastern France, each of them representing a different gradient between annual winter cereal crops and permanent grasslands. We mainly focused on carabids, though we also studied to some extent ground-dwelling spiders as well as pollinators such as hoverflies and lacewings. The landscape parameters were based on a land cover recording of cropped, grasslands and (semi-)natural areas and linear elements 500 m around every sampled location.Concerning carabids, cropland and grassland assemblages remained mainly distinct, but they showed higher similarity when located closer, up to 4 km from each other. Carabid activity-density was higher in the study regions with higher grassland coverage. In grasslands, we found a higher species richness when the landscape diversity around was increased, except for the study region which was strongly dominated by grassland. In winter cereal crops, the landscape parameters showed no significant effect on carabid species richness. Moreover, the common species richness in neighboring cereal fields and grasslands was enhanced by higher density of field borders between these two land cover types in the studied landscapes. Though the land cover type was by far the major determinant of carabid traits, landscape parameters also had a significant influence. Polyphagous species tended more to be commonly appearing in neighboring grassland and cereal crop. Phytophagous species were highly exclusive to grasslands, while predatory were it in cereal crops.Regarding other arthropod groups, we observed that the spider family richness was higher in permanent grasslands, though there were more individuals caught in cereal fields. Both hover flies and lacewings sampled density were higher in cereal fields and lower in the neighboring of higher grassland coverage.This thesis indicates that the preservation and restoration of a mosaic of permanent grasslands within diversely cropped landscapes is important for functional biodiversity. The inclusion of grasslands can enhance the diversity of beneficial arthropods and provide complementary resource and habitats to communities for pest control in crops.La biodiversité connaît un déclin préoccupant à l’échelle mondiale, les modifications et dégradations des habitats en demeurent l’une des causes principales. En Europe, la perte de biodiversité est étroitement liée à l’intensification de l’agriculture, qui a conduit à la simplification des paysages. En a résulté l’homogénéisation des paysages, où une faible diversité de cultures domine, ainsi qu’un agrandissement des parcelles. Les éléments naturels et semi-naturels, tels que les haies, les bandes enherbées ou les bosquets, furent retirés, alors que les prairies permanentes furent mises en culture ou abandonnées. Les prairies sont pourtant essentielles pour la biodiversité auxiliaire, car elles abritent et favorisent des espèces qui peuvent fournir lutte biologique et pollinisation à l’agriculture. Cette thèse propose donc de distinguer les influences de la parcelle, locale, et du paysage sur les communautés d’arthropodes de prairies permanentes et de cultures céréalières avoisinantes.Nous avons échantillonné des arthropodes d’appariement de céréales et prairies voisines, afin de comparer les effets de paramètres locaux et paysagers sur les biodiversités de ces deux couvertures du sol typiques des paysages agricoles. Nous avons mené ces travaux dans trois territoires différents, tous situés en Auvergne Rhône-Alpes. Chaque territoire était représentatif d’un gradient d’équilibre différent entre les couvertures en cultures annuelles et prairies permanentes. Notre intérêt s’est principalement porté sur les carabes, bien que nous ayons aussi étudié, dans une moindre mesure, les araignées ainsi que des pollinisateurs volants tels que les syrphes et les chrysopes. Les paramètres paysagers ont été établis à partir d’un recensement manuel de toutes les couvertures du sol, cultivées ou naturelles, ainsi que des éléments linéaires dans un rayon de 500 m autour de chaque site échantillonné.Les assemblages de carabes dans les prairies et céréales étaient très distincts, même s’ils ont présenté plus de similarités quand ils étaient plus proches, dans des parcelles distantes jusqu‘à 4 km l’une de l’autre. L’activité-densité des carabes était supérieure dans les territoires où la couverture globale en prairies permanentes était plus importante. Dans les prairies, nous avons trouvé une plus grande richesse spécifique dans des contextes paysager plus diversifiés, à l’exception du territoire fortement dominé par des prairies. Nos analyses n’ont pas mis en évidence d’effet du paysage sur la richesse spécifique des carabes dans les céréales. Par ailleurs, la richesse spécifique commune aux deux couvertures du sol était plus importante dans des contextes paysagers où céréales et prairies partageaient plus de bordures ensemble. Bien que le type de couverture du sol fût un facteur majeur dans la détermination des traits de vie des carabes, les paramètres paysagers eurent aussi leur importance. Ainsi, les espèces polyphages furent les plus sensibles d’être échantillonnées à la fois dans des prairie et céréale appariées. Les espèces phytophages ont ainsi été très souvent exclusivement échantillonnées dans les prairies, alors que les prédatrices l’étaient dans les céréales.Concernant les autres arthropodes, nous avons observé une plus grande richesse en familles d’araignées dans les prairies, bien qu’elles présentassent plus d’individus dans les céréales. Le nombre de syrphes et de chrysopes échantillonnés était plus important dans les céréales, et négativement influencé par la couverture paysagère en prairies.Notre thèse indique qu’il serait utile de préserver et restaurer une mosaïque de prairies permanentes dans les paysages agricoles diversifiés. Les prairies peuvent en effet améliorer la diversité auxiliaire des arthropodes et procurer des ressources complémentaires à leurs communautés