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Root-knot nematodes (RKNs) are major threats to crops through attacking the roots, which induces an abnormal development of the plant. Meloidogyne hapla is of particular concern, as it is currently expanding its distribution area and displays a wide host range. Effective plant protection against this RKN requires early detection, as even a single individual can cause severe economic losses on susceptible crops. Molecular tools are of particular value for this purpose, and among them, quantitative PCR (qPCR) presents many advantages (i.e., sensitivity, specificity, and rapidity of diagnosis at a reduced cost). Although a few studies have already been proposed for detecting M. hapla through this technique, they lack experimental details and performance testing, suffer from low taxonomic resolution, and/or require expensive hydrolysis probes. Here, we propose a qPCR detection method that uses SYBR Green with developed primers amplifying a fragment of the cytochrome oxidase I mitochondrial region. The method was developed and evaluated following the minimum information for publication of quantitative real-time PCR experiments (MIQE) guidelines to ensure its quality (i.e., sensitivity, specificity, repeatability, reproducibility, and robustness). The results demonstrate that the newly developed method fulfills its goals, as it proved specific to M. hapla and allowed for a reproductible detection level as low as 1.25 equivalent of a juvenile individual. All criteria associated with the MIQE guidelines were also met, so the method is of general use for the reliable early detection of M. hapla.

International audience; Current restrictions on the use of chemical nematicides have led to an increase in root-knot nematode (RKN) damages in horticultural crops. The effects of two sorghums as summer cover crops, Sorghum sudanense sudan-grass cv. ‘Piper’ or sudangrass hybrid [S. bicolor x S. sudanense] ‘270911’, respectively with low and high dhurrin contents, were compared in their ability to suppress RKN in a vegetable production system. The use of both sorghums ‘Piper’ and ‘270911’ as a green manure was found to be an effective strategy for decreasing RKN infestation in the soil, thereby protecting the subsequent planting of RKN susceptible crops (chard, lettuce or melon). Analytical experiments were further conducted in growth chamber and greenhouse pot experiments to investigate and compare the susceptibility of the sorghums and the factors affecting their efficacy for RKN management, in order to better explain the results obtained in the field trial. The two sorghums were poor hosts of RKN, acted as trap crops and as a biofumigant releasing hydrogen cyanide. Time of planting, time of bio-fumigation, and type of soil affected their efficacy for RKN management. For best RKN suppression, the sorghum cover crops need to be cultivated during one month or less and biofumigated for one month prior to crop planting. The trapping effect of both sorghums in clayey soil was less efficient than in sandy or sandy-loamy soils. Combining less than 30-days of sorghum culture and 10-days soil incorporation with solarization mulch was particularly efficient in suppressing nematodes. No effect relative to the sorghum type was detectable as long as they were used appropriatel.

Root-knot nematodes (RKNs) are major threats to crops through attacking the roots, which induces an abnormal development of the plant.

International audience; Ancient ecological legacies and past land use changes may inform on the present structure of biological communities. However, regions providing such successive ecosystems are scarce. In France, the Landes de Gascogne area provides such ecological shifts since a few ancient moorland, peatland and oak areas prior the afforestation with maritime pine (Pinus pinaster) 160 years ago still remain. Focusing on soil-borne parasites such as plant-parasitic nematodes (PPN), because forests were recently increasingly impacted by the introduction of intensive agriculture, this study is therefore aimed at comparing the diversity and the community patterns of these organisms at different scales (intra- and intersites) and between different successive ecosystems. The understory vegetation as well as the pedoclimatic characterization of the sampled sites were also considered. Common diversity indices were not impacted by this transition from ancient to past ecosystems. Although the most colonizer nematodes prevailed in all the ecosystems, PPN community structures significantly diverged between both ecosystems. In the logged pine forests, the sediment legacy could have primarily impacted the diversity. Moreover, the PPN diversity would mainly respond to the soil hydromorphicity that determined the associated understory vegetation. Consequently, a significant shift in community structure from moorlands to logged pine to logged pine forests was observed, regarding especially high pathogenic species such as Pratylenchus spp. Thus, analyzing PPN community structure highlights the PPN potential risk to consider during the introduction of intensive cropping systems.

International audience; Plant-parasitic nematodes (PPN) are detected everywhere as mixed-species communities. Most non-chemical control strategies of PPN only target some species, thus raising questions about the consequences that this specificity may have on the residual community. In this respect, the long-term ecological sustainability of such strategies is challenged. In order to evaluate the impacts of agronomical practices on PPN communities, two four-year experiments that differed by the presence or absence of root-knot nematodes (RKN - Meloidogyne spp.) were carried out under cold shelters in the south of France, under native field conditions of vegetable cropping systems that included a nematicidal sorghum green manure and a pepper variety carrying a RKN resistance gene. At the site with RKN, RKN populations developed on susceptible vegetables. They were controlled by the green manure but not by the R-pepper, and were also vulnerable to low soil temperatures. At the site without RKN, Paratylenchidae populations developed on susceptible vegetables, but were controlled by both the green manure and the R-pepper, and not by low temperatures. At each site, populations of Telotylenchidae exhibited dynamics suggesting competition with RKN or Paratylenchidae. Hypotheses about competition models are discussed according to the specific life traits of the PPN involved, including ecto- vs. endoparasitism and sedentary vs. free-living behaviour, and to the antagonist mechanisms of the cover and resistant crops that must be introduced in vegetable cropping systems.

Meloidogyne javanica is considered as the most damaging nematode of vegetables in Morocco. Eco-friendly bionematicides are urgently required for its control. In vitro experiments were carried out to assess the direct effect of bioproducts of Peganum harmala against M. javanica. The bioassay showed extracts to be nematotoxic. Aqueous extracts of P. harmala exhibited reversible nematostatic activity. The estimated ID50 of the most active product in methanolic extracts was 368ppm. HPLC-MS of the methanolic extract revealed that total content of major alkaloids of P. harmala was approximately 12.162±0.637mg/g. Harmine (8.514±0.521mg/g) is the dominant alkaloid. In conclusion, Peganum harmala has a reversible nematostatic activity on second stage juveniles of M. javanica. The effect of P. harmala is due to its possession of a high content of β-carboline alkaloids, which warrant further experimentation. Bioproducts from P. harmala should be exploited through formulations for management of the root knot nematode.

International audience; Plant-parasitic nematodes (PPN) are key impediments to efficient global crop production and impair the quality of susceptible plants in nurseries as well. In this context, nematode communities were determined in 305 solid substrate samples collected from 25 olive (Olea. europaea. subsp. europaea) nurseries in Morocco. Taxonomical and functional diversity as well as the structures of PPN communities were described and then compared between regions, cultivars as well as according to biotic and abiotic factors. A high diversity of PPN was observed, with the detection of 63 species and 26 genera. The most dominant taxa detected were spiral nematodes (Helicotylenchus spp. and Rotylenchus spp.), stunt nematodes (Tylenchorhynchus spp.), grazer nematodes (Tylenchus spp.) and root-knot nematodes (Meloidogyne spp.). Hoplolaimidae nematodes (Helicotylenchus spp. and Rotylenchus spp.) and Tylenchus spp. were better adapted to rainy conditions that prevailed in the northern regions of Morocco. Multiblock analyses demonstrated that functional diversity (cp and trophic groups) was more affected by the environment than taxonomical diversity (total number, species richness, locale diversity and evenness). They also indicated that PPN communities were more impacted by climatic variables (rainfall and minimum temperature) and nursery substrate origins than by soil physic-chemical factors. Nevertheless, a co-inertia analysis showed that N, P and K amendments in olive nurseries enhanced the development of harmful PPN, especially root-knot nematodes.

International audience; Root-knot nematodes are microscopic round worms, which cause severe agricultural losses. Their attacks affect the productivity by reducing the amount and the caliber of the fruits. Chemical control is widely used, but biological control appears to be a better solution, mainly using microorganisms to reduce the quantity of pests infecting crops. Biological control is developing gradually, and with time, more products are being marketed worldwide. They can be formulated with bacteria, viruses or with filamentous fungi, which can destroy and feed on phytoparasitic nematodes. To be used by the farmers, biopesticides must be legalized by the states, which has led to the establishment of a legal framework for their use, devised by various governmental organizations.

Plant-parasitic nematodes are major pests in agriculture. Microbial antagonists such as nematophagous fungi are of great interest for developing alternative biocontrol strategies to replace nematicide use. This study aims to isolate, identify and assess the diversity and the in vitro predatory activity of nematophagous fungi from various olive nurseries in Morocco. A total of 305 soil samples were collected in 25 nurseries in Moroccan olive-producing areas (Jbala, Guerouane, Haouz and Souss). Seventy-three pure fungal strains from nematophagous fungi were recovered from nursery substrates infested with root-knot nematodes. Diversity indices showed that fungi were more numerous in southern regions, whereas fungal communities were more numerically alike in northern regions, partly depending on the occurrence of root-knot nematodes. One fungal strain, Talaromyces assiutensis , killed all Meloidogyne javanica juveniles during in vitro predation tests. Orbiliaceae ( Arthrobotrys spp., Drechslerella brochopaga , Monacrosporium spp.) trapped 50 to 80% of juveniles. Purpureocillium and Trichoderma species killed 30 to 50% of juveniles. The diversity of nematophagous communities could be affected by the north-south climate gradient of Morocco, by their nematode prey expansion, and, to a lesser extent, by the habitat origin of the substrates used. Talaromyces assiutensis was the most efficient nematophagous species against M. javanica . The use of native nematophagous fungi is a promising alternative strategy for nematode control in olive nurseries and to prevent nematode introduction into olive orchards.

International audience; Root-knot nematodes are a growing concern for vegetable producers, because chemical nematicides are gradually disappearing. Alternative techniques based on agronomic practices are needed to solve the problem. This review analyzes the most recent studies related to these techniques and their combinations and identifies the most effective ones. Based on an agronomic point of view, the analysis focuses on a description of agricultural factors and practices, rather than on biological processes. Several alternative techniques are considered, including sanitation, soil management, organic amendments, fertilization, biological control and heat-based methods. We analyzed the effects of each practice and interactions among techniques and found large variations among studies. Many practices are only partially effective for nematode control; thus, combining control methods in a systemic analysis presents a challenge. We outline such an ongoing systemic approach and identify key future research studies.

Nematodes belonging to the genus Meloidogyne are the most ubiquitous and widespread plant-parasitic nematodes. They occur worldwide, are polyphagous and can parasitize most cultivated plants leading to reduced crop yields. They are especially harmful in developing countries because of the lack of suitable and feasible management strategies. Among all the control practices (chemicals, physical techniques, cultural practices, resistance), the use of natural enemies as biological control agents is the most recently developed. Pasteuria penetrans which is an obligate Gram-positive, endospore-forming bacterium, is perhaps the most promising plant-parasitic nematode biocontrol agent. Despite much research conducted on prey–predator interactions (host–parasite specificity, mechanisms of attachment, field efficacy), the influence of the soil environment on host–parasite interactions is poorly understood even when the soil appears to be the key factor. Beyond common studies on the influence of climatic conditions on the attachment of endospores of P. penetrans to nematodes, more knowledge about the systemic interactions between plants, soil water dynamics, soil texture and structure, and other biota on the parasitism of nematodes by P. penetrans would improve their utilization as biological control agents. The aim of this review is to analyze the literature dealing with the influence of the soil on nematode – P. penetrans interactions in order to suggest a helpful conceptual model based on partitioning the Pasteuria population in sub-populations according to their soil habitat (dispersible and non-dispersible aggregates, microporosity, macroporosity), not all of them being available for attachment and infection on nematodes. Such concerns should be taken into account by epidemiologists for improving biological management strategies based on the use of this bacterium.

International audience; Knowing which factors affect the distribution of organisms provides useful insights for the management of biodiversity. For root-knot nematodes Meloidogyne (RKN), a critical threat in agriculture, an understanding of the constraints that impact their diversity is a fundamental prerequisite for their control. RKN are reported to be major pests on olive trees, mainly in high-density orchards and in nurseries. This study was undertaken in order to characterise the Meloidogyne species associated with olive trees in Morocco and to consider how anthropogenic stresses and some edaphic and climatic factors may be involved in their spatial distribution. A soil sampling was conducted in the main olive growing areas in Morocco, including wild, feral and cultivated olive trees. RKN were detected in 12.2% of the samples. The analysis of biochemical (esterase patterns) and molecular (SCARS, D2D3) markers revealed the occurrence of M. javanica (as the predominant species), M. arenaria, M. hapla,M. spartelensis and of an undescribed species Meloidogyne n.sp. Some esterase variability was detected in M. javanica and M. hapla populations. The RKN species were distributed everywhere on an aggregated basis. However, M. javanica was recorded in high abundance throughout the cultivated areas in Morocco in high-density and traditionally cultivated olive orchards and rarely on some feral olive, while the other species were detected in low abundance on wild olive in mountain plant refuge areas in northern and southern Morocco. Nevertheless, the large distribution of M. javanica in cultivated areas could be primarily due to widespread introductions from nurseries, followed by multiple founder processes favoured by local conditions such as irrigation and planting density. In contrast, the detection of the other species hosted by wild olive only in plant refuge areas suggest that these areas host ancestral nematode species that did not disperse in the absence of human activities.

Farming activities that are likely to induce the development of emerging pests increasingly disturbs the Argan Biosphere in Morocco. Considering that plant-parasitic nematodes strongly contribute to the decrease in plant growth production, a survey was conducted in the Argan Biosphere in order to assess nematode diversity and distribution. It was established that the parasitic nematofauna was rich, with 70 species belonging to 34 genera and 12 families. Species with high plant decay potential belonging to Longidoridae, Heteroderidae, Hoplolaimidae, Meloidogynidae, Paratylenchidae and Pratylenchidae are present in the argan forest. Telotylenchus sp., Paratylenchus microdorus and Paratylenchus veruculatus , Xiphinema italiae and Xiphinema pachtaicum (virus-transmitting nematodes), and Helicotylenchus crassatus are the most dominant species. Populations of root-knot ( Meloidogyne spp.) and lesion ( Pratylenchus spp.) nematodes are also present. Climate forces have driven the structuration of the argan forest to topoclimatic landscapes that led the diversity of the plant-parasitic nematodes communities. The north–south typology of the arid climate affects the richness and the taxonomic and functional diversity of nematodes, while the west–east temperature typology mainly affects the abundance of nematodes, especially of colonizing species. The emergence of plant-parasitic nematode problems as a consequence of intensive agroforestry or argan orchard development is considered.

The epidemiology of Pasteuria penetrans, parasite of Meloidogyne javanica, was studied in a field cultivated with an African egg-plant (Solanum aethiopicum) in Senegal. Abiotic and biological parameters were analyzed from 100 soil samples. Soil physical characteristics were studied with principal component analysis (PCA). Similarity between the parameters according to biotic and abiotic variables was established by hierarchical classification and corroborated by Discrimin analysis (AFD). The coarser fractions (> 200 mu m) were positively correlated to intensive irrigation, whereas finest fractions (< 20 mu m) and spores of P. penetrans were abundant in the areas moderately irrigated. Furthermore, the proportion of Pasteuria-infected juveniles was positively correlated to the presence of finest texture and high water holding capacity. The abundance of M. javanica was associated with coarse sands and potassium. Based on these results, laboratory experiments were attempted on the influence of irrigation and soil texture on the distribution of P. penetrans in cultivated and bare soils. The results showed that 53% of the spores inoculated were leached by water flow in the sandy soil, but only 14% in the sandy-clay soil and 0.1% in the clay soil. No nematodes survived in the clay soil, while the population increased both in the sandy and the sandy-clay soils. More M. javanica were infected by P. penetrans in the sandy-clay soil than in the sandy soil. Comparing different combinations of bare soils containing 1.1-57% clay, the best spore percolation/retention balance occurred in soils textured with 10-30% clay.

International audience; Soil is a component of primary importance in crop production, even if it is often neglected, or only regarded as a physical support for the growth of plants. However, with the increasing societal concerns for the sustainability of agriculture, soil must be considered as a living system. Its quality results from the multiple interactions among physicochemical and biological components, notably the microbial communities, primordial for soil function. Crops are threatened by soil-borne diseases. These are often difficult to control, because of the “hidden” status of the pathogens and also because of the absence, noxiousness or lack of efficacy of chemical treatments. In this context, there is a renewed interest for cultural practices such as the use of organic amendments. These practices have a strong influence on soil health, which takes into account plant health, through both changes of physicochemical characteristics and influence on soil microbial communities. Cultural practices are used to improve soil health, and can, in some cases, increase soil disease suppression. The effects of these practices on soil properties have been studied, but the relationship between these properties and soil suppressiveness has not been always very clear. Many different soil descriptors, either abiotic or biotic, have been used to describe the soil health and suppressiveness, but there is a lack of identified, reliable and consistent indicators. One aim of this review is to show that, despite the age of the soil health concept and all the studies that have been conducted, there are still no guidelines for assessment of soil quality from the plant health point of view. Obviously, the extreme diversity of situations makes any generalisation from a given case-study difficult. However, based on what has already been done in related fields, a methodology to search for indicators of soil health can be proposed. In this review we will present (i) how a healthy soil can be defined and what are the concepts hidden behind the words “soil health,” (ii) which cultural practices have been used to control soil-borne diseases and their limitations, (iii) which soil parameters have been measured when studying soil suppressiveness, and which relationships have been found between these parameters, and finally (iv) how these descriptors could become indicators of soil health, using appropriate analytical and statistical methods.

National audience

Summary In Senegal, a study was carried out in a field cultivated with African egg-plant ( Solanum aethiopicum ) in order (1) to determine soil size fractions infested both with Meloidogyne javanica and Pasteuria , (2) to compare the efficacy of soil fraction dispersion methods in the recovery of both organisms and (3) to estimate the concomitant distribution of the two organisms in the different soil fraction sizes. Samples were taken from four areas: severely-infested (M+) with M. javanica with a high percentage (I+) of Pasteuria -infected juveniles, severely-infested (M+) with a low percentage of infected juveniles (I−), minimally-infested (M−) with a high percentage of infected juveniles (I+) and minimally-infested (M−) with a low percentage of infected juveniles (I−). The samples were dispersed and fractionated using two different techniques in order to evaluate soil aggregation (size fractions >200, 50–200, 20–50 and 0–20 μm). The numbers of free entities of Pasteuria penetrans were estimated per size fractions. The proportion of Pasteuria -infected juveniles (biological detection of P. penetrans ) was estimated in order to correlate the infection rate to the distribution of free entities of P. penetrans . Regardless of sampling area, the 50–200 μm size fraction predominated, followed by largest particle (>200 μm) size. The distribution of Pasteuria spores in the soil was not linearly correlated to the distribution of Pasteuria -infected juveniles. The influence of the soil characteristics on the relationship between the two organisms is discussed.

Pasteuria penetrans, a bacterial parasite of plant-parasitic nematodes, is used to control root-knot nematode Meloidogyne spp. populations in vegetable crops. But its efficiency is variable, mostly because of the patchy distribution of the bacteria in arable fields. As the infective P. penetrans are non-motile bacteria in soil, abiotic soil factors can affect the bacteria–nematode relationships. An epidemiological study, conducted in a vegetable field, showed that abiotic factors such as irrigation, soil water holding capacity and texture, affected the efficiency of P. penetrans. A correspondence analysis between these abiotic factors and the density of P. penetrans spores in the soil, and the proportion of Meloidogyne javanica juveniles infected by the bacteria, revealed that irrigation affected directly the distribution of the spores in soil pores related to their passive transport by water flow. Laboratory experiments conducted on the passive transport of spores confirmed that intensive irrigation leached the spores down the soil profile and decreased the percentage of infected Meloidogyne juveniles.

The transport of the spores of Pasteuria penetrans was studied in three contrasted textured soils (a sandy, a sandy-clay and a clay soils), cultivated with tomato, inoculated with juveniles of Meloidogyne javanica and watered with 25 or 150 mm day−1. One month after inoculation of the nematodes, 53% of the spores inoculated were leached by water flow in the sandy soil but only 14% in the sandy-clay soil and 0.1% in the clay soil. No nematodes survived in the clay soil, while the population was multiplied both in the sandy and in the sandy-clay soils. But juveniles of M. javanica were more infected by P. penetrans in the sandy-clay soil than in the sandy soil. Comparing different combinations of bare soils containing 1.1–57% of clay showed that the best spore percolation and retention balance occurred in soils amended with 10–30% clay. However, the spore recoveries decreased when the soil was enriched with more than 30% clay. The role of clay particles on the extractability of spores and on their availability to attach to the nematode cuticle in the soil is discussed.

National audience

International audience; Plant-parasitic nematodes affect significantly the production of susceptible plants, including olive trees. In this context, nematode communities were determined in soil samples collected from 23 olive growing sites in the Haouz and Souss regions (southern Morocco). These sites corresponded to various modalities: wild (Olea europaea L. ssp. sylvestris) or cropped olive (Olea. europaea L. ssp. europaea), traditional or high-density cropping, rainfed or irrigated. Even free-living nematodes prevailed in most of the sites, high population levels of plant-parasitic nematodes were observed in rainfed cropping systems than in irrigated systems. Ten nematode families and 14 genera were identified. The most important plant-parasitic nematodes detected, in order decreasing frequency of infestation (percentage of samples), were spiral nematodes Helicotylenchus spp. (100%) and Rotylenchus spp. (87%), lesion nematodes Pratylenchus spp. (100%) and root-knot nematodes Meloidogyne spp. (40%). Most of the nematode species were assigned to more or less colonizer nematodes, whereas only one family (Longidoridae) was assigned to persistent nematodes. Considering the two producing areas, plant-parasitic nematodes were significantly more abundant in the Souss region than in the Haouz region, but nematode diversity was higher in the second one. The prevalence of Meloidogyne spp. in the Haouz region would be related to the predominance of irrigated cropping systems in this region. Hoplolaimidae nematodes (Helicotylenchus spp. and Rotylenchus spp.) are better adapted to rainfed conditions that prevail in the Souss region. Co-inertia analysis showed the importance of soil physic-chemical characteristics (e.g., pH, texture and nutrients) on the structure of the plant-parasitic nematode community patterns. The high occurrence of Helicotylenchus spp. in olive orchards may be induced by fertilization. Aphelenchoides spp., Gracilacus spp., Pratylenchus spp., Rotylenchidae and Tylenchidae were supported by coarse textures as it was observed in the Souss region.

Differences in rates of infestation of root-knot nematode (Meloidogyne spp.) populations by the endospore-forming bacterium Pasteuria penetrans were not entirely due to inter/intra-specific variability of the organisms. Soil conditions, especially texture and chemical characteristics, are also involved. Focusing studies on vegetable crops, interactions between the occurrence of Meloidogyne spp. juveniles encumbered with spores of P. penetrans and some physico-chemical soil characteristics were analysed both between regions (West Africa, e.g. Burkina Faso and Senegal; South America, e.g. Ecuador; the Caribbean, e.g. Trinidad and Tobago; and Mediterranean Europe, e.g. Crete) and within Ecuador, Burkina Faso and Senegal. In Ecuador (clay or silty-clay soils), the mean proportion of infested juveniles was high (41.9%). In the sandiest soils, as in Senegal, there were very few infested juveniles (4.7%). In Crete, Burkina Faso, and Trinidad and Tobago, where the soils are siltier, the mean proportions of infested juveniles range between 14 and 24.4%. Multivariate analysis performed on the data from Senegal and Burkina Faso revealed that a significant increase of the mean clay content (1.4 and 10.5%, respectively) improved the mean proportions of infested juveniles (from 1.6 to 42.2% and from 10.7 to 79.4%, respectively). Influences of the soil texture and structure on the availability of the spores of P. penetrans to infest the juveniles of Meloidogyne spp. are discussed.

Plant-parasitic nematodes significantly contribute to economic losses in the ten top oliveproducing countries in the world, especially in the Mediterranean basin (Spain, Italy, Greece,Tunisia, and Morocco).Diversity and structures of plant-parasitic nematode communities respondto evolutionary, environmental and anthropogenic forces. Instead of controlling the main pathogenicnematode species as usual, one of the innovative strategies to control plant-parasitic nematodes wouldbe to manage diversity in communities in order to lead them to be less pathogenic. The present studyaims at understanding the contribution of olive domestication and human impacts on the plantparasiticnematode communities by analyzing the diversity of plant-parasitic nematodes in cultivatedolive compared to wild olive in Morocco. Thus, 220 samples were collected in 2012 in several sites withcultivated and feral olive trees (i.e. wild olive resulting from cultivated olive) in the olive production areaslocated all along the Atlas foothills, as well as on wild olive Morphobiometric observations revealeda significant diversity of plant-parasitic nematodes, belonging to 12 families and 28 genera. Our resultsshowed the presence of genera Pratylenchus and Meloidogyne in all sampled systems that are knownharmful taxa for agriculture especially in nurseries. These two genera were more abundant in thecropped systems. Principal component analysis revealed no significant effect of olive systems onthe diversity of PPN in communities but on the PPN community patterns Other factors such asolive genotype, soil physic-chemical characteristics, geo-climatic characteristics, associated plants witholive trees will also be discussed as major factors affecting the plant-parasitic nematode communitypatterns.

New developments in the estimation of free spores of #Pasteuria penetrans$, a hyperparasite of plant-parasitic nematodes, including #Meloidogyne$ spp., have been tested in contrasted textured soils. They were dedicated to improving the recovery of spores. Different methods of increasing energy of aggregate dispersion were compared in their efficiency in recovering spores inoculated in a sandy clay soil and a clay soil. The dispersion of the soils by the less energetic method (method A) allowed only 50% and 20% of the spore inoculum to be recovered from the sandy clay soil and clay soil, respectively. For these soils, 76% and 81% of the particle-size fraction (0-20 micrometers) isolated by this method were still aggregated in coarser structures. With increasing energy (methods B and C), these coarse aggregates disappeared entirely in both soils. At the same time, the recovery of spores increased sharply, representing about 87% and 75% of the inoculum of the sandy clay soil and clay soil, respectively. Therefore, at most 25% of the pool of spores remained undetectable. The formation of artificial aggregates during the enumeration procedure could not be advocated to explain this result, since the dispersion of the fraction collected for the enumeration did not improve spore recovery. (Résumé d'auteur)

The conclusions of a collaborative study of the occurrence and importance of root-knot nematodes (RKN, Meloidogyne spp.) and of their control agent, Pasteuria penetrans, in parts of Europe, Africa, South America and the Caribbean are presented. Rootknot nematodes were estimated to reduce the yields of a wide range of horticultural crops by > 25% in Ecuador, Malawi and Tanzania, and by ca 10% in Trinidad and Tobago. The greatest proportion of infected crops were observed in Ecuador (205 of 207) and the least in Trinidad and Tobago (70 of 174). The mean gall index was greatest in Ecuador (5.5). Levels of galling were least in Senegal (1.6), even though 89% of crops were infested and virulent M. mayaguensis was widespread. In all countries, M. incognita and M. javanica were the most abundant species, but M. hispanica occurred widely in Burkina Faso, even in newly cultivated areas in the Sahile. Several new esterase phenotypes were detected, especially in Ecuador and Malawi. Juveniles (J2) collected from the soil during the surveys were examined for attached spores of P.penetrans. It was widespread (20 to 60% of RKN populations), except in Malawi and Tanzania (< 10% were infected), and was found for the first time in Crete (Greece). Generally, < 50% of the J2 carried spores. The occurrence of P.penetrans was sometimes correlated with soil type e.g., in Senegal it was least frequent in sandy soils. Laboratory assays of the binding of spores of isolates of P.penetrans to populations of RKN indicated large variations in specificity and substantial interactions; differences between populations within a species of RKN were sometimes almost as great as those between species. In microplot trials in which an "exotic" isolate of P.penetrans was introduced (ca 103 spores per g soil), its incidence was not increased by increasing the frequency or intensity of the growing of RKN-susceptible crops. However, in two such trials at sites in Tanzania and Ecuador naturally infected with P.penetrans, there were large increases in the proportions of spore-encumbered J2 (up to 100% encumbered) and in the yields of spores (up to 3.3 × 106 spores per mg dry root) in those plots amended with an "exotic" isolate. In these plots, numbers of J2 in the soil were decreased and damage by RKN was suppressed; gall indices were decreased (from > 8 to < 3) and yields were increased (by up to 30%). No such changes were observed in the unamended control plots. Increased suppression of RKN was also observed in a field trial, even in plots where RKN-susceptible and non-host crops were alternated. Increased suppression following amendment with the "exotic" isolate of P.penetrans was not observed at sites not previously infected with P.penetrans. Regression analysis of the results from the microplot and field trials indicated that tomato yields were decreased by > 5% for every increase of one in the gall index. Yields were increased by alternating tomato with leguminous crops in some trials, but not in others. It is proposed that, in natural infections, mutual selection produces a dynamic balance between the P.penetrans and the RKN whereby levels of infection are rarely suppressive. However, the introduction of an "exotic" isolate of P.penetrans, with a different attachment profile, can disturb this balance, resulting in a greatly increased proportion of infected J2 and females, increased yields of spores and more suppression of RKN populations. Importance des nématodes à galles tropicaux (Meloidogyne spp.) et facteurs affectant l'utilité de Pasteuria penetrans, agent de contrôle biologique - Ce travail présente les conclusions d'une étude, menée en collaboration par plusieurs équipes de recherche, sur la présence et l'importance des nématodes phytoparasites du genre Meloidogyne et de leur parasite bactérien, Pasteuria penetrans, dans certains pays d'Europe, d'Afrique, d'Amérique du Sud et des Caraïbes. Les réductions de rendement de cultures maraîchères très diverses dues à ces nématodes atteignent 25% en Equateur, Malawi et Tanzanie, et 10% à Trinidad et Tobago. La plus forte proportion de parcelles infestées a été rencontrée en Equateur (205 sur 207) et la plus faible à Trinidad et Tobago (70 sur 174). C'est en Equateur que l'indice de galles moyen (égal à 5,5) était le plus élevé. Même si cet indice était faible en moyenne au Sénégal (1,6), 89% des cultures étaient infestées dans ce pays, en grande partie par l'espèce virulente M. mayaguensis. M. incognita et M. javanica sont les plus répandues dans tous les pays prospectés. Cependant, M. hispanica est très répandu au Burkina Faso, même dans des zones récemment cultivées en maraîchage en région sahélienne. Plusieurs phénotypes estérasiques nouveaux ont été détectés, spécialement en Equateur et au Malawi. Les juvéniles de second stade (J2) extraits des échantillons de sol collectés lors des prospections ont été examinés pour détecter la présence de spores de P.penetrans sur leur cuticule. Trouvé pour la première fois en Crète (Grèce), P.penetrans est très répandu dans les autres pays prospectés, infestant 20 à 60% des populations de Meloidogyne spp., sauf au Malawi et en Tanzanie où moins de 10% des populations sont atteintes. Le plus souvent, moins de 50% de J2 portent des spores bactériennes. Le taux de parasitisme des J2 par P. penetrans est influencé par les types de sols, comme par exemple au Sénégal où il est très faible dans les sols sableux grossiers. Des expériences en laboratoire portant sur l'attachement de spores de divers isolats de P. penetrans à des populations de Meloidogyne spp. ont révélé une grande variation de la spécificité et des interactions; les différences observées pour diverses populations d'une même espèce de Meloidogyne sont parfois presque aussi marquées que celles observées entre espèces. L'incidence parasitaire d'un isolat "exotique" de P. penetrans introduit dans des microparcelles (ca. 103 sporespar g. de sol) n'a pas été accrue par l'augmentation de la fréquence ou de la densité de plantation des cultures sensibles à Meloidogyne spp. employées. Cependant, dans deux microparcelles natullement infestées en P.penetrans, situées en Equateur et en Tanzanie, l'introduction d'un isolat "exotique" s'est traduite par un accroissement de la proportion de J2 infestés (jusqu'à 100%) et de la production de spores ((jusqu'à 3, 3 × 106 spores par mg [poids sec] de racines), d'une diminution de la population de J2 dans le sol, et d'une disparition des dégâts racinaires; les indices de galles moyens ont diminué (de plus de 8 à moins de 3) et les rendements des cultures ont augmenté (jusqu'à 30%). De tels changements n'ont pas été observés dans des sols non amendés en isolats "exotiques" de P.penetrans. Un meilleur contrôle des populations de Meloidogyne spp. a également été observé au champ, même lorsque la séquence culturale alternait des cultures sensibles et des cultures non-hôtes du nématode. Dans des parcelles non infectées en P.penetrans, la baisse des populations de Meloidogyne spp. n'a pas été observée après introduction d'un isolat "exotique" de la bactérie. Des analyses de régression portant sur les données obtenues en microparcelles ou au champ montrent que les rendements en tomate diminuent de plus de 5% chaque fois que l'indice de galle augmente d'une unité. Ces rendements ont parfois été améliorés lorsque des cultures de légumineuses alternaient les cultures de tomate. Ainsi, sur la base des analyses nématologiques et agronomiques faites en fin de cycles culturaux, il est suggéré que, dans les cas d'infestations naturelles en P.penetrans, des sélections mutuelles entraîneraient un équilibre dynamique entre les populations de la bactérie et celles du nématode, représentatif d'une densité-dépendance retardée. En revanche, l'introduction inondative d'isolats "exotiques" de P.penetrans, aux propriétés parasitaires différentes de celles des populations natives, pourraient rompre temporairement cet équilibre en faveur d'un accroissement de la proportion de nématodes (J2 et femelles) infestés et de la production de spores bactériennes, ainsi qu'un meilleur contrôle des populations de Meloidogyne spp. La capacité des populations de P.penetrans à survivre dans les sols et à contrôler durablement les populations de Meloidogyne spp. dépendraient de la spécificité entre les organismes, des propriétés des sols et des systèmes de culture.

International audience; The olive tree (Olea europaea ssp. europaea.) is one of the most ancient cultivated trees. It is an emblematic species owing to its ecological, economic and cultural importance, especially in the Mediterranean Basin. Plant-parasitic nematodes are major damaging pests on olive trees, mainly in nurseries. They significantly contribute to economic losses in the top-ten olive-producing countries in the world. However, the damages they induce in orchards and nurseries are specifically documented only in a few countries. This review aims to update knowledge about the olive-nematode pathosystem by: (1) updating the list of plant-parasitic nematodes associated with olive trees; (2) analysing their diversity (taxonomic level, trophic groups, dominance of taxa), which allowed us (i) to assess the richness observed in each country, and (ii) to exhibit and describe the most important taxa able to induce damages on olive trees such as: Meloidogyne, Pratylenchus, Helicotylenchus, Xiphinema, Tylenchulus, Rotylenchulus, Heterodera (distribution especially in the Mediterranean Basin, pathogenicity and reactions of olive trees); (3) describing some management strategies focusing on alternative control methods; (4) suggesting new approaches for controlling plant-parasitic nematodes based on the management of the diversity of their communities, which are structured by several environmental factors such as olive diversity (due to domestication of wild olive in the past, and to breeding now), cropping systems (from traditional to high-density orchards), irrigation, and terroirs.

Plant-parasitic nematodes are involved in soil fatigue processes in coastal foredunes and, therefore, have an impact on the growth of plants such as marram grass ( Ammophila arenaria ) that enhance sand accretion and the stabilisation of dunes. Transects were sampled in European Atlantic and Mediterranean foredunes at different locations. Plant-parasitic nematode communities and physico-chemical soil properties were analysed, and multivariate techniques were used to link them. Although all the dunes are of sandy texture, the Atlantic and Mediterranean dunes mainly differ by their ratio of coarse and fine sands. Mediterranean dunes, although more disturbed by storms than the Atlantic dunes, have fine-textured soils that can accumulate organic matter. They trap a large amount of minerals and have a high carbonate concentration due to the salinity of the Mediterranean Sea. As a result of the higher content of coarse sand in the top horizons, probably due to a higher accretion of sand, Atlantic foredune soils are low in organic matter and minerals. Soils from North and Irish Sea dunes have intermediate characteristics. These soil contrasts lead to specific plant-parasitic nematode communities. Thus, nematodes such as Hemicycliophora spp., Neodolichorhynchus spp., Longidorus spp. and Merlinius spp. generally colonise the carbonated and mineralised soils of the Mediterranean dunes, and do not seem to be affected by high salinity. Conversely, populations of Meloidogyne spp. and Pratylenchus spp. nematodes are more commonly found in coarse textured soils and the oligotrophic conditions that occur in Atlantic dunes. Specific local conditions such as the presence of paleosols do not seem to disturb them. Considering that both nematode species are major pests in cropping systems, higher population levels due to their fit to such soil characteristics can explain their contribution to soil fatigue encountered in Atlantic dunes.

International audience; Little is known about the variations of nematode mitogenomes (mtDNA). Sequencing a complete mtDNA using a PCR approach remains a challenge due to frequent genome reorganizations and low sequence similarities between divergent nematode lineages. Here, a genome skimming approach based on HiSeq sequencing (shotgun) was used to assemble de novo the first complete mtDNA sequence of a root-knot nematode (Meloidogyne graminicola). An AT-rich genome (84.3%) of 20,030 bp was obtained with a mean sequencing depth superior to 300. Thirty-six genes were identified with a semi-automated approach. A comparison with a gene map of the M. javanica mitochondrial genome indicates that the gene order is conserved within this nematode lineage. However, deep genome rearrangements were observed when comparing with other species of the superfamily Hoplolaimoidea. Repeat elements of 111 bp and 94 bp were found in a long non-coding region of 7.5 kb, as similarly reported in M. javanica and M. hapla. This study points out the power of next generation sequencing to produce complete mitochondrial genomes, even without a reference sequence, and possibly opening new avenues for species/race identification, phylogenetics and population genetics of nematodes.; Il existe peu de connaissances sur la variation des génomes mitochondriaux de nématodes, car leur séquençage avec une approche PCR reste difficile du fait de fréquentes réorganisations génomiques et de la faible similitude de séquence entre des lignées divergentes. Nous avons utilisé une approche d’écrémage de génome pour assembler la première séquence mitochondriale complète d’un nématode à galles (Meloidogyne graminicola). Un génome riche en AT (84,3 %) de 20 030 paires de bases (pb) a été obtenu avec une profondeur de séquençage supérieure à 300. Trente-six gènes ont été identifiés selon une approche semi-automatisée. La comparaison de cette séquence avec la carte physique du génome mitochondrial de M. javanica indique que l’ordre des gènes est conservé chez Meloidogyne. Toutefois, des réarrangements génomiques importants ont été observés entre genres de la superfamille Hoplolaimoidea. Des éléments répétés de 111 et 94 pb ont été détectés dans une longue région non codante d’environ 7500 pb, comme rapporté chez M. javanica et M. hapla. Cette étude montre le potentiel du séquençage de nouvelle génération pour produire rapidement des génomes mitochondriaux complets, même en l’absence de séquence de référence. Ceci ouvre des perspectives dans les domaines de l’identification d’espèces/races, de la phylogénie et de la génétique des populations de nématodes.

International audience; Background: Resistant cultivars are key elements for pathogen control and pesticide reduction, but their repeated use may lead to the emergence of virulent pathogen populations, able to overcome the resistance. Increased research efforts, mainly based on theoretical studies, explore spatio-temporal deployment strategies of resistance genes in order to maximize their durability. We evaluated experimentally three of these strategies to control root-knot nematodes: cultivar mixtures, alternating and pyramiding resistance genes, under controlled and field conditions over a 3-years period, assessing the efficiency and the durability of resistance in a protected crop rotation system with pepper as summer crop and lettuce as winter crop. Results: The choice of the resistance gene and the genetic background in which it is introgressed, affected the frequency of resistance breakdown. The pyramiding of two different resistance genes in one genotype suppressed the emergence of virulent isolates. Alternating different resistance genes in rotation was also efficient to decrease virulent populations in fields due to the specificity of the virulence and the trapping effect of resistant plants. Mixing resistant cultivars together appeared as a less efficient strategy to control nematodes. Conclusions: This work provides experimental evidence that, in a cropping system with seasonal sequences of vegetable species, pyramiding or alternating resistance genes benefit yields in the long-term by increasing the durability of resistant cultivars and improving the long-term control of a soil-borne pest. To our knowledge, this result is the first one obtained for a plant-nematode interaction, which helps demonstrate the general applicability of such strategies for breeding and sustainable management of resistant cultivars against pathogens.

National audience; Vegetable production makes an intensive use of pesticides, and a major challenge is to build alternative cropping systems that can control pests and diseases with fewer uses of chemical products. An on-farm analysis was conducted in Southeast France to assess the efficacy of several cropping systems in simultaneously controlling two major pests: root-knot nematodes (Meloidogyne spp.) and lettuce drop due to Sclerotinia sclerotiorum. Ten cropping systems resulting from the combinations of three crop sequences and two alternative techniques, solarization and green manure, were assessed during two years. The use of solarization once a year or once every two years limited the occurrence of S. sclerotiorum. Sorghum green manure tended to increase S. sclerotiorum incidence; the effect was positively correlated with green manure duration. Especially when no vegetable was cropped in summer, the green manure crop duration was lengthened and this probably created soil conditions favorable to the development of the fungus. The incidence of root-knot nematodes was largely dependent on crop rotation: a melon crop in summer increased its incidence on the subsequent lettuce crops whereas a summer sorghum cover crop had no effect. The cropping systems that limited Sclerotinia development in soil tended to support the root-knot nematode populations. These results should motivate farmers and advisers to adopt a systemic analysis and take into account the various interactions among inoculum level, soil characteristics, crop rotations, and technical management options for designing sustainable vegetable production systems.

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresUMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières; PESTOLIVE (Contribution of olive history for the management of soil-borne parasites inthe Mediterranean Basin) is a project funded by ARIMNet, an ERANET action supported bythe 7th European Framework Programme and by non-European Mediterranean countries.PESTOLIVE aims at producing knowledge and tools for a new and efficient management ofplant-parasitic nematodes (PPN) and plant-pathogenic fungi (PPF) in olive (Olea europaea L.)cropping systems and nurseries, while reducing the use of pesticides. Because of the anthropiccontinuum from Olea post-glacial refuges to Oleasters (domestication) and then to olive-trees(breeding and cropping), the fragmentation of the PPN and PPF communities and of theirnatural enemies could explain the scattered diversity of the control techniques (especiallyresistance rootstocks, biocontrol, cropping strategies) developed and applied all around theMediterranean Basin. The novelty of PESTOLIVE is based on: i) the analysis and themanagement of the parasite diversity (ecology of communities) instead of controllingemblematic species (population approach), and ii) the involvement of knowledge about thehistorical co-adaptation of soil-borne parasite and natural enemies communities to olive-treedomestication (origins and past assemblages) and breeding that follows the history of O.europaea around the Mediterranean Basin.

Different species ofArthrobotrys nematophagous fungi and several strains ofA. oligospora have been studied for their antagonistic effects against nematodes of the genusMeloidogyne, important pests of vegetables. All fungi trappedM. mayaguensis andM. incognita juvenilesin vitro but had no effect on the juveniles ofM. javanica. In pot experiments withM. mayaguensis, all fungi reduced the nematode populations and stimulated the growth of tomato seedlings. In a field trial, a strain of A.oligospora, isolated in Senegal and incorporated into compost blocks, was efficient in increasing the tomato seedling growth. The introduction of nematophagous fungi in compost blocks as a biological biocontrol technique against phytophagous nematodes adapted for developing countries is discussed.

International audience; A French programme, "Réseau de mesure de la qualité des sols: biodiversité des organismes" (RMQS BioDiv) was de-veloped in Brittany (27,000 km² in the western part of France) as an initial assessment of soil biodiversity on a regional scale in relation to land use and pedoclimatic parameters. The nematode community assemblages were compared among the land use categories. Crops were characterised by a high abundance of bacterial-feeders, particularly oppor-tunistic bacterial-feeders belonging to Rhabditidae. Meadows presented a higher total abundance of nematodes than did crops (20.6 ind·g −1 dry soil vs. 13.1 ind·g −1 dry soil), and they were mainly linked to the great abundance of plant-parasitic nematodes, particularly Meloidogyne, but with a very high heterogeneity between sampled plots. The nematodes were most abundant in forests (23.7 ind·g −1 dry soil) and presented the most structured community (SI = 82.2 in forests vs. 58.6 and 55.5 in crops and meadows, respectively). Forests had also the higher fungal component (fungal-feeders and facultative plant-feeders belonging to the Tylenchidae) leading to a significant higher part of the fungal decomposition pathway in forests than in crops. The ability of different taxonomic levels of nematode identifica-tion to discriminate among different cropping systems (i.e., continuous cropping system, crop with meadow in the rota-tion, meadow with crop in the rotation and permanent meadow) was also tested. The family level (48 families identified in these samples) was more efficient than the other taxonomic levels (86 taxa, 17 functional guilds and 6 trophic groups): best statistical significant discrimination for time spent in identification. The relation between the nematode ecological indices, the abundance of nematode trophic groups and the crop management practices were studied. The effects of fertilization, ploughing frequency, use of pesticides and management systems on ecological indices, particu-larly on the Maturity Indices, were observed.

Two strains (ORS 18692 S7 and ORS 18692 S5) of the nematophagous fungus Arthrobotrys oligospora have been isolated for the first time in Senegal. In vitro, both strains trapped 98% of groups of 7-day-old Meloidogyne mayaguensis juveniles within 48 h. Their optimal growth occurred at 25-30 C and at a pH of 5.6, but salinity inhibited their development. In order to test the fungi on M. mayaguensis in pots and in mixed populations of Meloidogyne spp. on tomato in the field, the fungus was incorporated into compost blocks before sowing and subsequent transplanting. In pot experiments during the cool season (28 C), both strains reduced nematode populations and stimulated seedling growth. In field trials during the hot season (35 C), both strains were efficient in reducing Meloidogyne populations. The feasibility of combining the use of compost blocks with the introduction of A. oligospora is discussed. Pour la premie re fois, deux souches du champignon ne matophage Arthrobotrys oligospora (souches ORS 18692 S5...

The susceptibility of two acacias (Acacia holosericea and A. seyal) against the root-knot nematode Meloiodogyne javanica has been studied. The nematode was inoculated at different rates (1000, 5000 and 10,000 second stage juveniles per seedling). In both acacias, M. javanica inhibited seedling height, shoot and root biomass and the density of root tips per mg of root. In terms of nematode development, the increase of M. javanica was greater on A. holosericea than on A. seyal when the inoculum rate was 1000 J2 per seedling indicating that A. holosericea is a better host for M. javanica than A. seyal.

International audience; The French programme Réseau de Mesures de la Qualité des Sols e Biodiversité was carried out at a regional scale (Brittany, west part of France) i) to produce a first statement regarding soil biodiversity, ii) to identify bioindicators of anthropic constraints, and iii) to determine baseline values for several biological groups depending on land uses. In this study, 109 monitoring sites were investigated using a systematic framework (a 16 km 16 km regular grid). Six biological groups were studied within four major categories, i.e., macrofauna (all soil macro-invertebrate taxa and earthworms), mesofauna (Acari and Collembola), microfauna (nematodes), and micro-organisms (microbial biomass and functional genes). The abundances of earthworms, nematodes, Acari and the bacterial community (assessed by their encoded 16S rRNA) as well as microbial biomass and earthworm species richness discriminate land uses (crops from meadows from forests). Macro-invertebrate abundance, Collembola abundance and richness, and nematode richness are only relevant for the discrimination of agricultural practices (e.g., management system or fertilisation intensity). Most of the soil biological groups (except Collembola) exhibit lower values of abundance and community richness in croplands than in meadows. This programme allows us to set up a first reference database for soil biological data for France covering microflora and fauna. This substantial reference database will be used to calibrate future research results and to develop management baseline values for stakeholders to assess the status of soil biodiversity under several policies, e.g., the Common Agricultural Policy, Soil Framework Directive, EU and national biodiversity strategies, and policies related to contaminated land management. Therefore it should assist stakeholders in the choice of good agricultural practices.

International audience; Plant-associated nematode species are supposed to cause marram grass (Amrnophila arenaria) decline in foredunes. But experiments with inoculated species populations have not proven any nematode effect on plant die out. Considering that nematode community patterns (ecological approach) would be more effective on plant growth than emblematic species (agronomical approach), a large survey in North (Belgium, France, The Netherlands, UK) and South (Portugal) European and in North African (Morocco) foredunes was conducted in order to analyse the diversity of the plant-associated nematode communities. It indicated that diversity (population levels, richness, diversity, evenness, trophic and colonizer/persister groups) does not differ between the communities sampled. But, the nematode community patterns are significantly impacted by climate and soil factors. Root-knot (Meloidogyne spp.) and lesion (Pratylenchus spp.) nematodes were more represented in Atlantic than in Mediterranean nematode communities, whereas cyst nematodes (Heterodera spp.) were more abundant in Northern than in Southern Atlantic nematode communities. Within the French nematode communities, the Atlantic communities strongly differ from the Mediterranean communities. It could be hypothesized that the sediment origin of the foredunes (e.g. Massif Central and Pyrenees for Atlantic sites vs Alps for Mediterranean sites) may be involved, because one Mediterranean site that showed an intermediate pattern is concerned by sediments from Massif Central origin. Knowledge about plant-associated nematode community structures in marram grass foredune ecosystems would help landscape managers for dune stabilization with plants. (C) 2011 Elsevier B.V. All rights reserved.

Le compartiment biologique des sols joue un rôle essentiel en délivrant des biens et des services écosystémiques clés, et il est impliqué directement et indirectement dans plusieurs fonctions du sol (cycle des nutriments, structure du sol, rétention de l'eau). La Commission Européenne a souligné l'intérêt de prendre en compte ce compartiment biologique. Elle a notamment demandé de développer des recherches sur ce thème dans les politiques de gestion des sols, en caractérisant la diversité spécifique et les fonctions biologiques de certains organismes du sol. Afin de répondre à de telles demandes et de réaliser un premier état de la biodiversité des sols à l'échelle régionale en relation avec les usages des sols et les paramètres pédoclimatiques, un programme français « RMQS BioDiv » a été mis en place sur les 109 sites du RMQS classique (Réseau de Mesure de la Qualité des Sols) en Bretagne. Un important réseau de collaborations scientifiques et de développement (12 équipes) a ainsi été créé pour étudier un très grand nombre de paramètres biologiques, à savoir la macrofaune (lombriciens, macrofaune totale), la mésofaune (collemboles et acariens), la microfaune (nématodes), et la microflore (biomasse microbienne, structure des communautés bactériennes et gènes fonctionnels), de même que des paramètres d'activité de la faune du sol (Humus Index). Ainsi, ce programme s'est appuyé sur le Réseau de Mesures de la Qualité des Sols (RMQS) mis en place à l'échelle nationale pour suivre l'évolution de paramètres physico-chimiques et d'usage des sols en utilisant un échantillonnage systématique (grille de 16 X 16 km) couvrant l'ensemble du territoire français. Le lien entre ces deux programmes, travaillant selon la même grille d'échantillonnage, permettra d'étudier les paramètres biologiques au regard des caractéristiques agro-pédoclimatiques, et devrait permettre d'établir des pistes de réflexion pour l'évaluation d'indicateurs biologiques pertinents de la qualité des sols. Les objectifs de cet article sont i) de présenter les protocoles et procédures mis en place dans le cadre du programme RMQS Bio Div pour l'étude des différents paramètres biologiques, ii) de décrire la gestion et le traitement des données, et iii) de présenter les premiers résultats obtenus. Ces résultats résultent de l'analyse de 109 sites bretons échantillonnés en 2006 et 2007, et montrent la distribution spatiale de différents paramètres biologiques., Soil biota play an essential role in delivering key ecosystem goods and services, and are both directly and indirectly responsible for many important functions (nutrient cycling, soil structure, water storage). European Union (EU) has underlined the interest of taking into account this biological compartment. EU has asked to develop biological researches in soil management policies, by characterizing biological species and biological functions of some soil organisms. To answer this request and make a first state at regional scale of soil biodiversity in relation to land use and pedoclimatic parameters, a French program « RMQS BioOiv » was developed on the 109 sites of Soil Quality Monitoring Network (RMQS) in Brittany. A large national research network (12 research teams) supported the program, that undertook the study of several biological parameters such as macrofauna (earthworms, total macro-invertebrates), mesofauna (Acarina and Collembola), microfauna (nematodes), and microflora (microbial biomass, community structure and functional genes), as well as biological activity parameters (Humus Index). So, this program leaned on RMQS which was developed at national scale to monitor physico-chemical soil parameters and land-use managements by using a systematic sampling (regular grid 16 X 16 km) covering the whole French territory. The link between these two programs, working on the same sampling grid, should allow the study of biological parameters in the light of soil and agricultural characteristics, and thus the definition of biological descriptors of soil quality. The objectives of this paper are i) to present the RMQS BioOiv program is terms of sampling design and protocols, ii) to describe the data management and treatment, and iii) to show some results as a first instance of the data analysis to be carried out in this program. Results were obtained from the analysis of 109 sites sampled in 2006 and 2007 across the Brittany Region, and showed the spatial distribution and density of the different biological groups.

Root-knot nematodes belonging to the Meloidogyne genus are ubiquitous plant-parasitic pests, especially on vegetables. The Pasteuria penetrans bacterium is an obligate parasite of nematodes, parasitizing most of the Meloidogyne species. Spatial distributions of Meloidogyne javanica populations infested or not by P. penetrans and of bacterial populations were studied in a vegetable plot naturally infested by these organisms. It was observed that distributions of M. javanica populations, of populations infested by P. penetrans, and of free bacteria populations were not overlapped. Soil factors involved were investigated. Soil texture and water flow in porosity are concerned, as they directly influence the level of the pool of bacteria and then the chances of both organisms to meet. The soil solution has a direct effect on the attachment of the bacterium on the nematode cuticle.

International audience; Soil biota play an essential role in delivering key ecosystem goods and services, and are both directly and indirectly responsible for many important functions (nutrient cycling, soil structure, water storage). European Union (EU) has underlined the interest of taking into account this biological compartment. EU has asked to develop biological researches in soil management policies, by characterizing biological species and biological functions of some soil organisms. To answer this request and make a first state at regional scale of soil biodiversity in relation to land use and pedoclimatic parameters, a French program « RMQS BioOiv » was developed on the 109 sites of Soil Quality Monitoring Network (RMQS) in Brittany. A large national research network (12 research teams) supported the program, that undertook the study of several biological parameters such as macrofauna (earthworms, total macro-invertebrates), mesofauna (Acarina and Collembola), microfauna (nematodes), and microflora (microbial biomass, community structure and functional genes), as well as biological activity parameters (Humus Index). So, this program leaned on RMQS which was developed at national scale to monitor physico-chemical soil parameters and land-use managements by using a systematic sampling (regular grid 16 X 16 km) covering the whole French territory. The link between these two programs, working on the same sampling grid, should allow the study of biological parameters in the light of soil and agricultural characteristics, and thus the definition of biological descriptors of soil quality. The objectives of this paper are i) to present the RMQS BioOiv program is terms of sampling design and protocols, ii) to describe the data management and treatment, and iii) to show some results as a first instance of the data analysis to be carried out in this program. Results were obtained from the analysis of 109 sites sampled in 2006 and 2007 across the Brittany Region, and showed the spatial distribution and density of the different biological groups.; Le compartiment biologique des sols joue un rôle essentiel en délivrant des biens et des services écosystémiques clés, et il est impliqué directement et indirectement dans plusieurs fonctions du sol (cycle des nutriments, structure du sol, rétention de l'eau). La Commission Européenne a souligné l'intérêt de prendre en compte ce compartiment biologique. Elle a notamment demandé de développer des recherches sur ce thème dans les politiques de gestion des sols, en caractérisant la diversité spécifique et les fonctions biologiques de certains organismes du sol. Afin de répondre à de telles demandes et de réaliser un premier état de la biodiversité des sols à l'échelle régionale en relation avec les usages des sols et les paramètres pédoclimatiques, un programme français « RMQS BioDiv » a été mis en place sur les 109 sites du RMQS classique (Réseau de Mesure de la Qualité des Sols) en Bretagne. Un important réseau de collaborations scientifiques et de développement (12 équipes) a ainsi été créé pour étudier un très grand nombre de paramètres biologiques, à savoir la macrofaune (lombriciens, macrofaune totale), la mésofaune (collemboles et acariens), la microfaune (nématodes), et la microflore (biomasse microbienne, structure des communautés bactériennes et gènes fonctionnels), de même que des paramètres d'activité de la faune du sol (Humus Index). Ainsi, ce programme s'est appuyé sur le Réseau de Mesures de la Qualité des Sols (RMQS) mis en place à l'échelle nationale pour suivre l'évolution de paramètres physico-chimiques et d'usage des sols en utilisant un échantillonnage systématique (grille de 16 X 16 km) couvrant l'ensemble du territoire français. Le lien entre ces deux programmes, travaillant selon la même grille d'échantillonnage, permettra d'étudier les paramètres biologiques au regard des caractéristiques agro-pédoclimatiques, et devrait permettre d'établir des pistes de réflexion pour l'évaluation d'indicateurs biologiques pertinents de la qualité des sols. Les objectifs de cet article sont i) de présenter les protocoles et procédures mis en place dans le cadre du programme RMQS Bio Div pour l'étude des différents paramètres biologiques, ii) de décrire la gestion et le traitement des données, et iii) de présenter les premiers résultats obtenus. Ces résultats résultent de l'analyse de 109 sites bretons échantillonnés en 2006 et 2007, et montrent la distribution spatiale de différents paramètres biologiques.

affiche, résumé; Soil biota play essential roles in delivering key ecosystem goods and services, and are both directly and indirectly responsible for acting in many important functions (nutrient release, soil structure maintain, contribution to water storage). It is thus essential to characterize both the species diversity and the biological functions. In order to monitor soil biodiversity (species and function) in relation to land use (mainly agricultural practices) and pedoclimatic parameters, a French program « RMQS-biodiv » was developed at a wide regional scale (Brittany). An important national research collaboration (12 research teams) supported the program, that undertook the study of several biological parameters such as macrofauna diversity (earthworms, total macro-invertebrates), mesofauna diversity (acarina and collembola), microorganisms (nematodes diversity, microbial biomass, bacterial and fungal diversity), as well as functional biological parameters (soil respiration, humus index, macrofauna and mesofauna activity: biogenic structure, feeding activity). This program was connected to a larger soil monitoring network developed at national scale (Soil Quality Measurement Network- RMQS) which monitored soil parameters (chemistry, physic) and agricultural management using a regular grid (16 X 16 km) covering the whole national territory. The link between these two programs allowed the study of biological parameters in the light of soil and agricultural characteristics, and thus the definition of biological indicators. The results obtained from the analysis of 115 sites sampled in 2006 and 2007, will be discussed in terms of relevance of these biological criteria as indicators, and in fine of their transfer to field actors (technicians) who are in charge of new tool implementation on agronomical management assistance. Furthermore, the results will also be discussed with respect to propositions and recommendations made by the ENVASSO project (Environmental Assessment of Soil for Monitoring), especially the biological criteria proposed by the European project and the hierarchy of these criteria.

International audience

The nematodes specificities and their interactions with plants are reviewed, considering host plants quality and compatibility. The potentials of nematode resistance and diversity of antagonists and parasitism are discussed, in relation to host specificity and obligate multitrophic relationships. The ecology and management of nematode communities are also reviewed, focusing on soil health approaches and new paradigms for plant protection.

Tsetse flies transmit African trypanosomes, responsible for sleeping sickness in humans and nagana in animals. This disease affects many people with considerable impact on public health and economy in sub-Saharan Africa, whereas trypanosomes' resistance to drugs is rising. The symbiont Sodalis glossinidius is considered to play a role in the ability of the fly to acquire trypanosomes. Different species of Glossina were shown to harbor genetically distinct populations of S. glossinidius. We therefore investigated whether vector competence for a given trypanosome species could be linked to the presence of specific genotypes of S. glossinidius. Glossina palpalis gambiensis individuals were fed on blood infected either with Trypanosoma brucei gambiense or Trypanosoma brucei brucei. The genetic diversity of S. glossinidius strains isolated from infected and noninfected dissected flies was investigated using amplified fragment length polymorphism markers. Correspondence between occurrence of these markers and parasite establishment was analyzed using multivariate analysis. Sodalis glossinidius strains isolated from T. brucei gambiense-infected flies clustered differently than that isolated from T. brucei brucei-infected individuals. The ability of T. brucei gambiense and T. brucei brucei to establish in G. palpalis gambiensis insect midgut is statistically linked to the presence of specific genotypes of S. glossinidius. This could explain variations in Glossina vector competence in the wild. Then, assessment of the prevalence of specific S. glossinidius genotypes could lead to novel risk management strategies.

Currently, the abundance of Pasteuria penetrans in soils, an unculturable bacterial parasite of root-knot nematodes (Meloidogyne spp.), is estimated by the percentage of nematode juveniles infected with bacteria and the number of spores attached to their cuticle. Indirect immunofluorescence led to detection of free spores directly in soil suspensions using UV light and polyclonal antibodies raised against two P. penetrans populations (ORS-21414-Sen and PP1). Three extraction methods were compared in order to improve spore recovery. A gentle shaking/sieving method recovered more than 90% of the spores inoculated in soils and was more efficient and simple than aqueous two-phase partitioning and polyethylene glycol extractions. All the spores inoculated in sandy or sandy–clay soils were detected with immunofluorescence microscopy. The quantification of the spores was improved using an ELISA technique that showed a good correlation between optical density and spore concentration in inoculated soils. Specific antibodies provide a suitable method to quantify P. penetrans and may be used to follow the evolution of the real pool of bacteria either in native suppressive soils or in inoculated ones.