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Not just mutations: Inbreeding depression persists without genetic variation
No full textInbreeding depression (ID), the decline in fitness upon inbreeding, is thought to result from a decrease in genetic heterozygosity enhancing phenotypic effects of recessive deleterious mutations. However, emerging evidence suggests that mutations may not explain ID completely. In this study, we test whether ID can emerge even in contexts where genetic heterozygosity does not vary. To that end, highly inbred lines ( F =0.99999997) of the freshwater snail Physa acuta were used to produce individuals with varying levels of parental relatedness (self-fertilization, sibling crosses, and cousin crosses), though with identical genomic heterozygosity. Several fitness traits declined significantly with increasing parental relatedness, a pattern characteristic of ID, and quantitatively representing a non-negligible fraction of the ID usually observed in natural, genetically diverse populations of Physa acuta . Individual-based simulations showed that mutation rates compatible with values of ID found in natural populations are way too low to generate as much ID as observed in our experiment. These findings are consistent with the hypothesis that epigenetic changes, in addition to mutations, could contribute to a rapid regeneration of ID and explain the persistence of detectable ID in sets of genetically identical individuals
Abrupt physico-chemical changes in the limnology of Pyrenean mountain lakes necessitate urgent management actions
No full textData and all codes for this paper are available and permanently archived on the Figshare repository (https://doi.org/10.6084/m9.figshare.26039245, https://figshare.com/s/30b2f6b98be75abc893f).ECA&D project (https://www.ecad.eu)International audienceMountain lakes are rare ecological niches supporting unique species assemblages and are important sources of safe drinking water for wildlife, livestock and humans. Located at high altitude, these lakes are vulnerable to environmental stressors such as climate or land-use change, impacting their ecosystem functions. However, although trends in water temperature and physico-chemical composition have been fairly well studied in large mountain lakes, the same cannot be said for small-to medium-sized shallow lakes. Here, using measurements of the water chemistry of 25 Pyrenean mountain lakes and temperature records for 14 of them, we show that the environmental conditions which prevail in their littoral zones have undergone rapid changes between 2007 and 2023. Over this 16-year period, we found that, on average, the duration of the ice-cover period decreased by 58.35 days, and the average annual water temperature rose by 1.65 °C. We also found a significant overall decrease in pH, total organic carbon and nitrogen, as well as a significant increase in hardness and dissolved potassium. Our results demonstrate rapid abiotic environmental alterations in mountain lakes, with potential negative implications for humans, wildlife, livestock and ecosystem functioning. Likely consequences include declines in aquatic biodiversity, a degradation in the quality of drinking water and increased health risks from harmful algal blooms. Policy must urgently acknowledge the impacts of global change in mountains in order to take the necessary management actions
Oxygen and hydrobiological profiles of homemade manure-based tea in North Africa
No full textInternational audienceHomemade manure tea (HMT) is commonly used in North Africa to enhance crop yields. Yet their physicochemical and biological characteristics remain poorly understood. This study evaluated oxygen and hydrobiological profiles of three types of HMT (bovine, ovine and poultry based, respectively noted HMTb, HMTo, HMTp) and compared them to control solutions of water and water supplemented with soluble NPK fertilizer. For these three types of HMT, oxygen and hydrobiological profiles were measured daily over a 7-day incubation period in three repeated, identical experiments, each comprising randomized treatments and five repetitions per treatment. Our results show that all HMT types rapidly transitioned to hypoxic conditions in the first 24h, shifting to anoxia between day 2 and day 7 depending on HMT type. This anoxic environment promoted denitrification and led to elevated NH 4 + concentrations, suggesting the presence of anammox and microaerobic processes. Particulate organic matter contents and bacterial densities were highest in HMTp, while ciliate densities were highest in HMTb. These findings underscore the bioactive potential of HMT as fertilizers, with HMTp showing a favorable nitrogen profile beneficial for agricultural applications. To maintain aerobic conditions longer and reduce nitrogen losses and greenhouse gas emissions, we recommend passive or mechanical aeration, applying HMT during cooler hours, and stabilizing the pH of HMT. This study offers valuable insights to refine HMT preparation protocols, enhancing their use as bioactive fertilizers
Mapping seasonal flood-recession cropland extent in the Senegal River Valley
No full textInternational audienceFlood-recession agriculture (FRA) represents a crucial source of livelihood for numerous communities across Africa who reside near expansive floodplains and wetlands. However, it is currently insufficiently monitored. In this study, we present a methodology for mapping FRA harvested areas in the Senegal River Valley that is both reproducible and scalable. Our methodology entails the integration of optical and radar data from Sentinel platforms, conducted through a multitemporal analysis with a seasonal focus, and the application of the Random Forest algorithm. The results, supported by a kappa coefficient of 91.9%, demonstrate the first comprehensive mapping of FRA in the Senegal River valley, conducted between 2019 and 2023. This mapping facilitates the identification of the hydrological factors that influence FRA harvesting. The results of the analyses have demonstrated the importance of interannual variability in the cultivated areas of FRA, which range from 14,000 to 75,000 ha depending on the intensity of the annual flood. The duration and flooded extension are the primary factors that regulate the cropping pattern of FRA over the floodplain. The flood duration must be around 35 days to permit the cultivation, with growth generally starting between 10 and 30 November. In consideration of these findings, we recommend that future water management strategies and rural development initiatives give due consideration to FRA, to enhance the visibility of farmers
A framework for the sustainable maintenance of permanent runoff management structures in rainfed agriculture under climate change
No full textInternational audienceRainfed agriculture supports a significant share of global food production, balancing water storage with competing demands through runoff management. Human interventions to manage runoff range from temporary practices (e.g., tillage adjustments, crop choice) to permanent structures such as terraces and ditches. While practices are adaptable, structures are less flexible but critical for climate resilience. Their life-cycle comprises design/construction, maintenance, abandonment/destruction, and rehabilitation. Despite extensive research on design, rehabilitation, and abandonment, the description, understanding, and impact of maintenance practices remain understudied. This paper addresses this gap through a configurative review (1954–2024), integrating scattered knowledge. We show that rainfall variability, driven by climate change, accelerates biophysical degradation (e.g., terrace deformation, ditch occlusion), requiring adaptation and knowledge sharing to ensure structural stability and hydrological connectivity. Results highlight how regional inconsistencies in structure names hinder cross-regional comparisons and research consolidation. Our contributions include: (1) a standardized framework for context-specific evaluation of maintenance practices and (2) an assessment of runoff management structure efficiency under climate change. By integrating biophysical durability, socioeconomic feasibility, and adaptive governance, this framework provides stakeholders and academic actors with a common basis for systematically evaluating and improving runoff management. In practice, we urge policymakers and practitioners to adopt proactive, climate-adaptive maintenance, and to incentivize local community involvement for hybridizing traditional knowledge and technical innovation. By integrating maintenance into farming system design and management, these structures may effectively mitigate the impacts of an increasingly unpredictable climate, ensuring long-term resilience and sustainability in rainfed agriculture
Verrous et leviers institutionnels de réduction de pesticides dans l'agriculture tropicale. Un éclairage par l'Afrique de l'Ouest et du Centre
No full textPolicy Brief Initiative PRETAGIn a context of growing awareness of the harmful effects of pesticides on human health and biodiversity, their use in tropical agriculture is increasing sharply. This paradox raises the question about institutional barriers and levers to reduce their use, including agroecological alternatives. Our results show that, despite new regulations on the international level, policies supporting pesticides continue unabated. This support distorts technological competitiveness to the detriment of reducing pesticide use. Potential institutional levers for reduction have been identified. Specifically, they suggest that better information should be provided on the burden of pesticide costs on public budgets and the investment needed in agro-ecological innovations.Dans un contexte marqué par la connaissance croissante des effets délétères des pesticides sur la santé humaine et la biodiversité, leurs usages sont en forte augmentation dans les agricultures tropicales. Ce paradoxe soulève la question de la connaissance des verrous et leviers institutionnels à la réduction d'usages, dont les alternatives relevant de l'agroécologie. Nos résultats montrent que, malgré de nouvelles régulations à l'échelle internationale, les politiques de soutien aux pesticides ne faiblissent pas. Ces soutiens engendrent des distorsions de compétitivité technologique au détriment de la réduction d'usage. Des leviers institutionnels potentiels d'une réduction ont été identifiés. Ils proposent notamment de mieux renseigner le poids du coûts des pesticides dans les budgets publics et les investissements nécessaires dans les innovations portées par l'agroécologie
New, Complete Circularized Genomes of Xanthomonas citri pv. mangiferaeindicae Produced from Short- and Long-Read Co-Assembly Shed Light on Strains that Emerged a Decade Ago on Mango and Cashew in Burkina Faso
No full textInternational audienceWe report high-quality genomes of three strains of Xanthomonas citri pv . mangiferaeindicae, the causal agent of mango bacterial canker disease, including the pathotype strain of this pathovar and two strains from Burkina Faso that emerged a decade ago. These strains hosted two to three plasmids of sizes ranging from 19 to 86 kb. Genome mining revealed the presence of several secretion systems and effectors involved in the virulence of xanthomonads with (i) a type I secretion system of the hlyDB group; (ii) xps and xcs type II secretion systems; (iii) a type III secretion system with several type III effectors, including transcription activator-like effectors; (iv) several type IV secretion systems associated with plasmid or integrative conjugative elements mobility; (v) three type V secretion system subclasses (Va, Vb, and Vc); and (vi) a single i3* type VI secretion system. The two strains isolated in Burkina Faso from mango ( Mangifera indica) and cashew ( Anacardium occidentale) differed by only 14 single-nucleotide polymorphisms and shared identical secretion systems and type III effector repertoires. Several transcription activator-like effectors were identified in each strain, some of which may target plant genes previously found implicated in disease development in other xanthomonad-associated pathosystems. These results support the emergence in Burkina Faso a decade ago of very closely related strains that became epidemic on mango and cashew (i.e., two distinct host genera of a same plant family). These new genomic resources will contribute to better understanding the biology and evolution of this agriculturally major crop pathogen
The impact of background risk on altruistic giving
No full textThis paper investigates the effect of an additive unfair background risk on the optimal donation behavior of a purely altruistic decision-maker in the dictator game. Assuming both the dictator and the recipient face this background risk, and that the dictator is risk-vulnerable, we find that the presence of background risk reduces the deviation of the optimal donation from an equal split. This outcome holds whether the dictator's fairness is evaluated ex-ante or ex-post, offering new insights into the implications of risk vulnerability
Comparaison de trois variétés d'arachide en zone sub-saharienne : rendement, état sanitaire et interactions symbiotiques avec les organismes du sol
No full textCe volume fait suite aux Rencontres Francophone Légumineuses (RFL) de mars 2024 organisées par le Cirad, INRAE, Terres Inovia et Terres Univia, et co-organisé par l'Institut Sénégalais de Recherches Agricoles (ISRA). Ce rendez-vous unique entre tous les acteurs du développement, des filières et de la recherche sur les légumineuses à graines et fourragères. L’occasion de croiser les regards, partager les connaissances et accélérer l’innovation autour des légumineuses.Les RFLs s’intéressent aux légumineuses à graines, fourragères ou ligneuses, et visent à couvrir la diversité des systèmes de production, ainsi que la diversité des usages : alimentation humaine, animale et non-alimentaire.Les légumineuses sont un levier majeur pour relever les défis mondiaux du changement climatique et de la sécurité alimentaire et nutritionnelle. Partout dans le monde, elles disposent d’un rôle stratégique : atouts nutritionnels, souveraineté protéique et alimentaire. Les nombreuses espèces de légumineuses constituent également un formidable vivier d’innovations alimentaires.National audienceTo increase groundnut yields in Senegal, research has developed technical proposals. However, a systemic vision is needed to evaluate their performance in the context of farmers' fields. We compared three short-cycle groundnut varieties: Fleur 11, 55-33 and 55-437, on two farmers' fields with contrasting soil fertility levels, interacting with two levels of mineral fertilization and rhizobial inoculation. Trials were conducted in 2018, a year marked by a long rainfall break in during the vegetative phase of the crop. Varieties 55-33 and 55 437 reached half of their potential yield, while Fleur 11 only reached a quarter. Fleur 11 variety was severely affected by fungal diseases causing seedling mortality and pod rot. These diseases were particularly severe on the least fertile field. Effects of fertilizer application on yields were the lowest in the least fertile field. With an average of 114 nodules plant-1, the varieties showed a good nodulation capacity, suggesting effective nitrogen fixation. Fertilizer application stimulated nodulation, suggesting that nutrient availability, particularly phosphorus, is a limiting factor for symbiotic nitrogen fixation in these agroecosystems. Mycorrhization was intense, particularly on the least fertile soil. Bacterial inoculation had no effect on the measured variables. Stepwise regression showed that the variability in seed yield was primarily linked to soil carbon content and damage from soil-borne diseases, while fodder yield was primarily linked to the number of nodules per plant. While often ignored in current crop models, soil-borne diseases represent a major obstacle to improving groundnut yields and its symbiotic interactions with soil organisms in the studied agroecosystems. Combining disease resistance, symbiotic efficiency, and good fertilizer response, varieties 55-33 and 55-437 are valuable tools for improving the productivity of groundnut crops in marginal environments.En vue d'accroître les rendements de l'arachide au Sénégal, la recherche a élaboré des propositions techniques. Cependant, une vision systémique est nécessaire pour évaluer leurs performances dans le contexte des parcelles d'agriculteurs. Nous avons comparé sur deux parcelles d'agriculteurs aux sols contrastés par leurs niveaux de fertilité, trois variétés d'arachide à cycle court : Fleur 11, 55-33 et 55-437, en interaction avec deux niveaux de fertilisation minérale et d'inoculation rhizobienne. Les essais ont été conduits en 2018, une année marquée par une longue pause pluviométrique pendant la phase végétative de la culture. Les variétés 55-33 et 55-437 ont atteint 50% de leur rendement potentiel, alors que Fleur 11 n'a atteint que 25% de son rendement potentiel. La variété Fleur 11 a été fortement affectée par les maladies fongiques causant des mortalités de plantules et des pourritures de gousses. Ces maladies ont été particulièrement importantes au niveau du champ le moins fertile. Les effets de l'apport d'engrais sur les rendements ont été les plus faibles sur le champ le moins fertile. Avec une moyenne de 114 nodules plant -1 , les variétés ont montré une bonne capacité de nodulation, suggérant une fixation d'azote efficace. L'apport d'engrais a stimulé la nodulation, suggérant que la disponibilité en nutriments, notamment le phosphore, est un facteur limitant pour la fixation symbiotique d'azote dans ces agrosystèmes. La mycorhization des variétés a été intense, particulièrement sur le sol le moins fertile. L'inoculation de bactéries n'a eu d'effets sur les variables mesurées. Une régression pas à pas a mis en évidence que la variabilité du rendement de graines était en priorité liée aux teneurs en carbone du sol et aux dégâts des maladies telluriques, alors que le rendement de fanes était en priorité lié aux nombres de nodules plant - 1 . Alors qu'elles sont souvent ignorées dans les modèles de culture actuels, les maladies telluriques représentent un obstacle majeur à l'amélioration des rendements de l'arachide et de ses interactions symbiotiques avec les organismes du sol dans les agrosystèmes étudiés. En combinant résistance aux maladies, efficacité symbiotique et bonne réponse aux fertilisants, les variétés 55-33 et 55-437 constituent des outils précieux pour améliorer la productivité des cultures d'arachide en milieu marginal
Estimation des nombres de reproduction de base et effectif de la sharka
No full textInternational audienc