Portail Hal-l'Institut Agro Rennes-Angers
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Les contrats de production en grandes cultures: des stratégies de différenciation sur le marché.
No full textChapitre 6International audienc
Discussion on “Continuous-space occupancy models” by Wilson J. Wright and Mevin B. Hooten
No full textInternational audienceWithin the family of models designed to estimate species presence, known as species distribution models (SDMs), occupancy models account for imperfect detection. While there are multiple available options to perform SDMs in continuous space, this is not the case for occupancy models. Wright and Hooten (in press) propose a very interesting approach to fill this gap. They propose a novel approach using a clipped Gaussian process to infer species presence over continuous space, instead of the traditional site-based occupancy models. Their proposition has significant potential, and we examine it further from both practical and ecological perspectives
Research note: double digest Restriction site Associated DNA sequencing is a suitable alternative to high density SNP chips for genomic selection of layers
No full textInternational audienceFor the genomic selection of laying hens, the costs of genotyping are still a challenge. Alternative genotyping approaches as low density SNP chips have been developed by breeding companies to avoid the use of the high-density SNP chip (HD). Another approach called double digest restriction site associated DNA sequencing (ddRAD-seq), associated with an appropriate quality control was also proven to be reliable to genotype laying hens. From this perspective, the use of ddRAD-seq genotypes as an alternative to HD SNP chip genotypes was studied for the genomic evaluation of 179 candidate individuals in a commercial pure line of laying hens of Rhode Island.Genomic evaluations based on ancestry were performed in three different scenari and for four egg quality traits. The first scenario is the reference scenario using only HD SNP chip genotypes. The genomic estimated breeding values (GEBV) were calculated for the 179 candidates with 437 individuals as the reference population (GEBVHDchip437). In the second scenario, the reference population included only the 50 individuals with true ddRAD-seq genotypes and GEBVddRAD-seq50 were calculated for the 179 G1 candidates, based on their ddRAD-seq genotypes. Finally, for the third scenario of genomic evaluation, the reference population was constituted of 437 individuals, with simulated ddRAD-seq genotypes. The GEBVddRAD-seq437 were calculated for the 179 G1 candidates based on their true ddRAD-seq genotypes.Then, Spearman correlations were calculated between GEBVddRAD-seq50 or GEBVddRAD-seq437 and the reference GEBVHDchip437.The mean rank correlation between GEBVHDchip437 and GEBVddRAD-seq50 was 0.92. The mean correlation between GEBVHDchip437 and GEBVddRAD-seq437 was 0.98. The reduced reference population of the GEBVddRAD-seq50 scenario didn't permit for a good representation of the genetic diversity in the population. But, with an equivalent reference population, genomic evaluation based on ddRAD-seq genotypes achieves similar results as genomic evaluation based on HD SNP chip genotypes
Use of transglutaminase for the production of lactose hydrolyzed milk powders
No full textInternational audienceFor population with lactose maldigestion, many dairy products with hydrolyzed lactose have been developed. However, spray drying of lactose hydrolyzed milk powder has challenges such as adhesion to the surface of drying chamber, reduced solubility and a tendency for caking (Torres et al., 2017). The use of transglutaminase (TGase) has shown modified techno-functionalities of several dairy products. Moreover, TGase treatment was found to improve flowing behavior and an increase in the transition temperature (Er et al., 2019) of skim milk powder. In our study, we explored the potential of TGase to address challenges related to lactose hydrolyzed milk powder. Four different skim milks (control, lactase-added, TGase-added, lactase and TGase-added) were concentrated 40% dry matter content and spray-dried at the pilot scale (n=3). Key characteristics such as the product adhesion to the equipment, the biochemical composition, particle size distribution and the presence of Maillard reaction markers were determined. Electrophoresis showed a decrease in the intensity of the casein bands in TGase-added powder, confirming glutamine-lysine crosslinking by TGase.. Our findings shows that the use of Tgase.did not affect the dryability of the milk but increased the particle size of the powders without altering their bimodal conformation. TGase did not affect the hydrolysis of lactose nor the color of the powders. However, the content of 5-hydroxymethylfurfural increased significantly in TGase-added powder suggesting different Maillard reaction pathways compared to the other powders. Thus, this study leads to new hypotheses and possibilities for future research to elucidate the influence of TGase addition on Maillard reaction mechanisms. Moreover, investigating the functionality of the powders such as rehydration properties could provide more insights into the potential application of TGase
Insights into the triggering factors and determination mechanisms of host alternation in aphids
No full textInternational audienceThe bird cherry-oat aphid Rhopalosiphum padi, is one of the ten percent of aphids that are host alternating. The annual life cycle of R. padi entails an obligatory migration between a primary woody host, Prunus padus (Rosaceae), where sexual reproduction occurs, and many secondary hosts of the Poaceae family, where successive generations reproduce parthenogenetically. Migration between the two types of host plants is achieved by specialized migrant morphs. Very little is known about the cues that trigger migrant development, host alternation establishment and the underlying mechanisms. In this study, we aimed to elucidate the key steps involved in migrant induction and determination of host alternation, and to shed light on these intricate processes. We found that when first or second instar larvae of R. padi were placed on mature leaves of P. padus they developed into migrant morphs, while exposure to young leaves resulted in the development of wingless individuals that remain on the primary host. We also demonstrated the gradual establishment of acclimation to the secondary hosts that precedes the migration step. Finally, we showed that the switch to feeding on the alternative hosts is irreversible once emigrants have reached adulthood. These results not only allowed us to define the critical periods of the leaf stage associated with morph induction and determination, but also to pinpoint the emigrants' developmental stages when acclimation to secondary hosts begins. These novel insights of these critical periods will facilitate the investigation of molecular changes associated with host alternation in aphids
Inférence statistique multi-omique de l'hétérogénéité cellulaire - IGDR SCAN 26/03/2025
No full textInternational audienc
Biological control mitigates spread of vector-borne plant pathogens
No full textInternational audienceDiseases caused by vector-borne plant pathogens cause adverse impacts on yield resilience, food security, and farmer livelihoods, which are bound to aggravate under global change. Biological control is routinely discounted as a mitigation strategy for plant diseases, partially due to scarce and inconclusive empirical support. Here, using curated field survey data for 58 persistently or semi-persistently transmitted pathogens, we employ a multimethod approach to assess the role of resident (i.e., naturally occurring) biological control agents in these pathosystems. Our meta-analyses show how in planta pathogen incidence is strongly affected by vector abundance and infectivity. Meanwhile, biological control agent density negatively affects vector abundance and slows vector population build-up. Together, these relationships suggest that biological control lessens pathogen incidence by reducing vector abundance, though a paucity of data impedes direct, empirical demonstration of this effect. In particular, bipartite (mainly vector × pathogen) interactions have only been uncovered under field conditions for less than half of focal pathosystems. More so, just 5 % of studies simultaneously reported pathogen, vector, and biological control agent densities. Our study contests the long-standing dogma that arthropodvectored pathogens cannot be mitigated through biological control, and accentuates how observational or manipulative field studies are imperative to grasp its full potential
Programme MigrenMer : synthèse et valorisation des connaissances disponibles sur les migrateurs amphihalins en mer
No full textInternational audienceLes poissons migrateurs amphihalins, essentiels à l’équilibre des écosystèmes aquatiques,connaissent un déclin alarmant en raison des pressions anthropiques. Une meilleure connaissancede la biologie et de l’écologie de ces espèces pendant leur phase marine est essentielle pour mieuxadapter les stratégies de gestion. Le programme MigrenMer, initié en 2019, a permis de constituerune base de données inédite issue de plus de 168 000 opérations de pêche. Grâce à une approchede modélisation innovante, les chercheurs ont pu cartographier leur répartition et évaluerla pertinence des aires marines protégées. Ces résultats constituent une avancée majeure pourorienter les stratégies de gestion et renforcer les mesures de conservation de ces espèces menacées
Regular-fat and low-fat dairy foods and cardiovascular diseases: Perspectives for future dietary recommendations
No full textInternational audienceMost current dietary guidelines for the prevention of cardiovascular diseases (CVD) recommend the consumption of low-fat dairy in place of regular-fat dairy foods, one of the main sources of dietary saturated fatty acids (SFAs). Here, we summarize the data presented and discussions held-relating to the validity of such recommendations-between a panel of international nutrition research experts at a high-level closed workshop on \"Saturated Fat in Dairy and Cardiovascular Diseases,\" which took place in Amsterdam on 15-16 April, 2024. The most recent evidence indicates that overall, consumption of milk, yogurt and cheese, irrespective of fat content, is neutrally associated with CVD risk. There is also no evidence yet from randomized controlled trials that consumption of regular-fat milk, yogurt, and cheese has different effects on a broad array of cardiometabolic risk factors when compared with consumption of low-fat milk, yogurt, and cheese. Thus, the body of evidence does not support differentiation between regular-fat and low-fat dairy foods in dietary guidelines for both adults and children. Strategies focusing primarily on reduction of energy-dense, nutrient-poor foods, the main source of SFAs in Western diets, rather than on the fat content of dairy foods, are more likely to benefit the population's cardiovascular health. Future research is needed to understand better the place of regular-fat and low-fat dairy foods within healthy eating patterns
