HAL-CIRAD
Not a member yet
54841 research outputs found
Sort by
New data on an old pest complex: The status of Phlyctinus callosus Schönherr and Phlyctinus xerophilus Haran (Coleoptera: Curculionidae) in South Africa
No full textMaterial was collected under Cape Nature Permits Numbers CN35-28-13395 and CN44-30-4229, and with permission from private landowners.International audiencePhlyctinus is an endemic weevil genus of the Cape Floristic Region that comprises eight to ten species, previously classified under the monotypic P. callosus sensu lato concept. Two species of this genus, Phlyctinus callosus and P. xerophilus, are of economic concern to the deciduous fruit and grapevine industry in the Western Cape province of South Africa, causing primary damages and being of phytosanitary concern at the adult stage. The taxonomic revision conducted in 2020 raised doubts whether one of the two species was a newly emerging pest and/or what species was considered in studies before the clarification of species boundaries. Also unclear is whether these species can be controlled similarly using current control measures. The aim of this study therefore is to review the pest status of the two species over time based on museum records, field collections and historical publications, and to clarify how control measure(s) are impacted. We infer that neither species appear to be emerging pests in the region, both being of agricultural significance for at least 80 years. Phlyctinus callosus is mostly distributed along the southern coast, while P. xerophilus is distributed in inland valleys. The two species show similar biology, physiology and ecology in agro-ecosystems, and can be excluded from the host plant canopy using stem-barriers, adults being flightless. As such, it is shown that the naming of P. xerophilus as a pest is mainly a taxonomical clarification within a pre-existing species complex
Steinernema yirgalemense (Steinernematidae) to control Phlyctinus callosus and Phlyctinus xerophilus (Curculionidae)
No full textWeevils were collected under Cape-Nature permit no. CN35-28-13395 and with permission from the above-mentioned landowners.International audienceConsiderable progress has been made in the surveying, taxonomy, screening, mass production and formulation of entomopathogenic nematodes (EPN) and their associated symbiotic bacteria in South Africa. Steinernema yirgalemense isolate 157-C is one of the most promising native EPN candidates with regards to virulence, its broad insect-host spectrum, and can be readily mass-produced and formulated into a commercial product. The banded fruit weevils, Phlyctinus callosus sensu stricto and Phlyctinus xerophilus , previously grouped together under the Phlyctinus callosus sensu lato species concept, are native entimine weevils of economic importance to deciduous fruit, grapevine and berries in the Western Cape province of South Africa. This study investigated potential differences in baseline susceptibility of larvae and pupae of the two weevil species to S. yirgalemense in laboratory screenings. The test arena used was 24-well bioassay plates, with an inoculation concentration of 200 infective juveniles (IJ) insect −1 for larvae and 100 IJ insect −1 for pupae. Infection was determined 48 h and 96 h after inoculation. Field-efficacy of S. yirgalemense , applied at a concentration of 60 IJ cm −2 , against larvae of the two weevil species was determined in an ecologically relevant semi-field trial. In all cases in vitro mass-produced IJ of S. yirgalemense were used. No baseline differential susceptibility between P. callosus and P. xerophilus larvae was obtained in laboratory screenings. Phlyctinus pupae were approximately twice as susceptible compared to larvae, with significant differences between bioassay batches. Approximately 45% control of P. xerophilus larvae was obtained after 96 h of exposure to S. yirgalemense in the field, differing significantly from the control and P. callosus treatment. Low levels of Phlyctinus larval infection by native EPN (confirmed as Heterorhabditis bacteriophora from one P. xerophilus cadaver) occurred in both control and EPN treatment groups under field conditions
Multiple nutrient limitation of the soil micro-food web in a tropical grassland revealed by nutrient-omission fertilization
No full textInternational audienceAlthough involved in key functions of the terrestrial ecosystems, the activity and the diversity of soil microorganisms can be severely limited by energy and nutrients in weathered tropical soils. To optimize nutrient cycling for crop nutrition, assessing which nutrients limit the activity of the microbial food web is thus essential. This was our aim in this study carried out on a tropical ferrallitic soil from a natural grassland in Madagascar. For this purpose, we employed an innovative nutrient-omission approach in microcosms to test the distinct effects of omitting C, six nutrients (N, P, K, S, Ca, Mg) and a cocktail of micronutrients (B, Mn, Cu, Na and Mo) on the composition, biomass and activities of the microbial community and on the abundance and biomass of their nematode grazers. C and P were identified as primary limitations, but other nutrients (N, Mg and S) played significant roles as co-limiting factors. Some bacterial and fungal taxa were significantly associated to specific nutrient deficiencies and can act as biological indicators. Additionally, the abundance and biomass of microbial-feeding nematodes provided valuable insights into the responses of the soil microbial community to nutrient deficiencies. These findings contribute to our understanding of nutrient dynamics and microbial community growth in tropical grassland ecosystems and have implications for sustainable crop fertility management and ecosystem ecology in similar environments
Le lait de chamelle au risque de l’économie politique : de l’économie du don à l’économie marchande
No full textInternational audienceLe lait de chamelle a longtemps été exclu du marché compte tenu de sa seule disponibilité dans les régions parmi les plus reculées de la planète. Ce contexte est sans doute en partie à l’origine de la conviction qu’avaient les éleveurs chameliers selon laquelle, la vente de lait de chamelle relevait d’un « tabou » à qui on donnait éventuellement une dimension religieuse. Pourtant, associée uniquement à l’économie du don, cette posture a radicalement évolué en quelques décennies vers une économie marchande pour une part capitaliste. Le présent article tente de mobiliser ces concepts d’économie du don et d’économie marchande pour comprendre les mutations en cours et s’appuie sur l’exemple du Sultanat d’Oman pour illustrer ce que peut signifier la marchandisation du lait de chamelle. Le cas du Sultanat d’Oman est emblématique au sens où l’évolution y est récente et extrêmement rapide dans un contexte environnemental et socio-politique tout-à-fait particulier. Si les changements évoqués s’appuient sur l’exemple omanais, ils apparaissent largement universels et expliquent la forte croissance attendue de ce commerce du lait à l’échelle mondiale et pas seulement dans les pays traditionnellement producteurs
Exploring social indicators in smallholder food systems: modeling children’s educational outcomes on crop-livestock family farms in Madagascar
No full textInternational audiencePromoting smallholders’ sustainable development in Africa means addressing agronomic and economic factors but also highly relevant social influences shaping farmers’ production and affecting household well-being. Holistic, integrated analyses can help to meet this need, informing more effective policies and interventions for smallholder farming systems. The authors apply a transdisciplinary, quantitative approach to analyzing social impacts in the smallholder context, using milk-producing crop-livestock family farms in central Madagascar as a test case. First, stochastic frontier analysis is leveraged to confirm education as a social indicator linked to production efficiency. Then, linear regression is used for exploratory modeling of children’s educational outcomes. Findings from the Malagasy case emphasize the influence of rural infrastructure, parental education, chronic poverty, family planning, and crop-livestock diversification on children’s educational outcomes among one region’s farming households. Taken together, results suggest that Madagascar’s policymakers should consider comprehensive territorial planning for simultaneously promoting agricultural development and human well-being. This study illustrates how a transdisciplinary approach to social impacts analysis can integrate agronomic, economic, and social dynamics and help anticipate potential outcomes in support of smallholders’ sustainable development
Tree Pólya Splitting distributions for multivariate count data
No full textIn this article, we develop a new class of multivariate distributions adapted for count data, called Tree Pólya Splitting. This class results from the combination of a univariate distribution and singular multivariate distributions along a fixed partition tree. As we will demonstrate, these distributions are flexible, allowing for the modeling of complex dependencies (positive, negative, or null) at the observation level. Specifically, we present the theoretical properties of Tree Pólya Splitting distributions by focusing primarily on marginal distributions, factorial moments, and dependency structures (covariance and correlations). The abundance of 17 species of Trichoptera recorded at 49 sites is used, on one hand, to illustrate the theoretical properties developed in this article on a concrete case, and on the other hand, to demonstrate the interest of this type of models, notably by comparing them to classical approaches in ecology or microbiome
Combining UAV and Sentinel-2 Imagery for Estimating Millet FCover in a Heterogeneous Agricultural Landscape of Senegal
No full textInternational audienceIn recent decades, remote sensing has been shown to be useful for crop cover monitoring over smallholder agricultural landscapes, such as agroforestry parklands. However, the fraction of green vegetation cover (FCover) has received little attention. Indeed, the collection of FCover ground data representative of the within-field heterogeneity is time-consuming. Thus, this article aims to bridge this gap by proposing an original methodological framework combining FCover data derived from unmanned aerial vehicle (UAV) and Sentinel-2 (S2) images for estimating millet FCover at the landscape scale in an agroforestry parkland of the groundnut basin of Senegal during the 2021 and 2022 cropping seasons. UAV-based FCover was computed over a 3 m x 3 m grid using a thresholding approach for six dates over the cropping seasons and then used as ground observation for the upscaling of millet FCover at the landscape scale with S2 data. Various spectral vegetation indices and textural features were derived from S2, and several modeling approaches based on machine learning algorithms were benchmarked. Our results showed that the modeling approach using the full-time series in combination with a random forest algorithm was able to explain 73% (root mean square error = 12.13%) of the UAV-FCover variability after validation in 2021 and 2022. In addition, UAV images are suitable for consistent monitoring of millet FCover over heterogeneous agricultural landscapes by training S2 satellite images. To further check its robustness, this approach should be tested for different crops and practices across a variety of agricultural landscapes in sub-Saharan Africa
Ancient diversity within Diporodrilus (Crassiclitellata, Annelida) clarify the historical biogeography of Corso-Sardinian earthworms
No full textInternational audienceCorsica and Sardinia are amongst the largest islands of the Western Mediterranean. Their complex geological history included belonging to the European-Iberian continental margin (close to current-day Catalonia and Provence) and varying degrees of isolation for the last 30 million years, leading to peculiar, highly endemic faunas and floras. This is especially true for their earthworm faunas, which include endemic species of several Lumbricoidea genera and the endemic family (or subfamily) Diporodrilidae. Only three species have been described for the morphologically unique Diporodrilus, but there exists evidence for wide morphological variability within them and the existence of several species-level genetic lineages within Corsica. This work aimed to investigate the genetic diversity and phylogenetic relationships between the genetic lineages of Diporodrilus from Corsica and Sardinia (based on the sequences of 5 mito-nuclear markers), to perform an integrative systematics revision combining species delimitation techniques and morphological data, and to obtain a time-calibrated phylogeny of Diporodrilus and other Corso-Sardinian Lumbricoidea. Within 15 populations of the morphospecies Diporodrilus omodeoi and Diporodrilus pilosus across Corsica and Sardinia, 10 species-level genetic lineages were detected. Phylogenetic independence, high genetic divergence and morphological differences provided the support for the description of five new pseudocryptic species: Diporodrilus rotundus sp. nov., Di. jorgei sp. nov., Di. minor sp. nov., Di. meridionalis sp. nov. and Di. telti sp. nov. Time-calibrated phylogenetic inference estimated the age for genus Diporodrilus at 65.9 Mya; even if other Corso-Sardinian genera were significantly younger, all of them presented deep divergences predating the break-off of the microplate from the continent. The almost threefold increase in the known diversity of Diporodrilus stresses the need for comprehensive earthworm diversity inventories in both Sardinia and Corsica, and for studies on their ecological role and conservation status. The close correspondence between some geological and cladogenetic events suggest that the distribution of Corso-Sardinian earthworms could be used to inform standing geological controversies
Investigating the multi-disease challenge in apricot through single and multienvironment genome wide association studies
No full textInternational audienceOver their entire lifetime, apricot trees are exposed to a wide range of pests and diseases incurring for significant sanitary impacts and economic losses. Several sources of partial resistances have been identified but the underlying genetic architecture has yet to be elucidated for most diseases. In this study, the objective is to identify the genetic components underlying resistance – or low susceptibility – of two major diseases in apricot: blossom blight (Monilinia spp.) and leaf rust (Tranzschelia spp.). To do so, a core collection composed by 150 accessions replicated in 5 randomized blocs was grown under low phytosanitary conditions in two environmentally contrasted locations in South-East of France. These accessions have been densely sequenced with the Illumina HiSeq 2000 NGS technique. After monitoring rust and blossom blight damages from 2020 to 2023, we dissected the observed phenotypic variation into genotype, environment and their interactions effects via descriptive statistics and variance decompositions. To identify genetic markers linked to resistance components, we firstly performed genome wide association studies (GWAS) for each environment separately. We found stable genetic effects across the environment, reflected by robust quantitative trait loci (QTLs). In contrasts, some QTLs were only detected in a specific set of trial. To jointly analyse site-specific GWAS results and improve statistical power, we used a meta-analysis GWAS approach. By using a random effect procedure, we were able to consider the heterogeneity of the QTL effects across environments and the correlation between the single-environment GWAS. In the last approach we performed multi-environment GWAS with the MTMM package to dissociate QTLs from QTL by environment interactions effects. The present results provide insights into the genetic basis of blossom blight and rust susceptibility in apricot and therefore contribute to the development of genomics-assisted breeding to improve biotic resilience in apricot varieties
Attitudes and preferences of the Moroccan consumer towards fruits : the case of the midelt apple (Morocco)
No full textInternational audienceIn this paper, we review and discuss the factors that affect consumer preferences and attitudes towards fruit. The objective is to provide a theoretical framework for an empirical study to identify the factors influencing the Moroccan consumer's purchase decision of the "Midelt" apple produced by farms in the Draa-Tafilalet region. A survey was conducted on a sample of 343 consumers, to study the factors that influence their attitudes towards local apples and their intention to buy the Midelt apple.Dans cet article, nous passons en revue et discutons les facteurs qui affectent les préférences et les attitudes du consommateur vis-à-vis des fruits. L’objectif est de fournir un cadre théorique pour la réalisation d’une étude empirique afin d’identifier les facteurs influençant la décision d’achat du consommateur marocain de la pomme de « Midelt » produite par les exploitations agricoles de la région Draa-Tafilalet. Une enquête a été réalisée sur un échantillon de 343 consommateurs, pour étudier les facteurs qui influencent leurs attitudes envers les pommes locales et leur intention d’achat de la pomme de Midelt