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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.

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.

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.

Background Root-knot nematodes (RKN) are major pest of olive tree (Olea europaea ssp. europaea), especially in nurseries and high-density orchards. Soil samples were collected from main olive growing areas of Morocco, to characterize Meloidogyne species and to discuss the contribution of biotic and abiotic factors in their spatial distribution. Results RKN were found in 159 soil samples out of 305 from nurseries (52.1% occurrence) and in 11 out of 49 soil samples from orchards (23.2% occurrence). Biochemical and molecular characterisation (PAGE esterase and SCAR) revealed the dominance of M. javanica both in nurseries and orchards with minor presence of M. incognita only in nurseries, and M. arenaria in only one nursery. RKN were distributed on aggregated basis. Frequent presence of M. javanica in orchards might have come from nurseries. In contrast, the detection of M. incognita in nurseries alone suggests that this species could not reproduce in orchards because of either the competition with other plant-parasitic nematodes or unfit local habitats. The impact of environmental variables (climate, habitat origin and physicochemical characteristics of the substrates) on the distribution of Meloidogyne species is also discussed. Conclusion Olive nurseries in Morocco are not able to guarantee the safety of rooted plants. As a result, olive production systems are exposed to strong RKN invasion risks. Consequently, the use of healthy substrates in nurseries may prevent plant-parasitic nematode induction in orchards.

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.

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.

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.

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.

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.

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.

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.

Abstract An aqueous extract from leaves of Crotalaria virgulata subsp. grantiana was assayed for its effects on second-stage juveniles of Meloidogyne incognita. The biological activity was nematostatic; nematodes were not killed but were completely paralysed in a 1 mg/ml (w/v) extract: the LD50 equivalent was estimated to be 0.5 mg/ml. The effect was reversible: juveniles previously paralysed by C. grantiana extract recovered complete mobility in water and were able to infest a susceptible tomato plant. Freeze-dried aqueous extract from C. grantiana leaves added to a sterile sandy substrate at 1 mg/ml protected susceptible tomato plants from M. incognita infestation. This suggests a promising use of C. grantiana as both a green manure and natural alternative to synthetic chemicals in nematode population control, especially in integrated pest management for vegetable crops in organic agriculture of tropical and temperate areas.

The in vitro paralysis of second-stage juveniles of Meloidogyne incognita, M. javanica and M. mayaguensis by aqueous extracts of 15 West African Crotalaria species was analysed. A multivariate analysis distinguished four groups, based on their nematostatic activity: i) C. glaucoides extracts were not active; ii) the root extracts from C. goreensis, C. lathyroides and C. perrottetii were more active than the shoot extracts; iii) the shoot extracts from C. comosa and C. cylindrocarpa were more active than the root extracts; iv) both shoot and root extracts of C. atrorubens, C. barkae, C. grantiana, C. hyssopifolia, C. pallida, C. podocarpa, C. retusa, C. senegalensis and C. sphaerocarpa have nematostatic effects depending on either the Crotalaria species or plant tissue from which the extracts were derived. However, considering the greater biomass contribution of the leaves and stems compared to the roots when the plants are used as green manure, C. barkae, C. grantiana, C. pallida and C. podocarpa are the most efficient Crotalaria species, whatever the Meloidogyne species targeted.