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Design and assessment of innovative Mediterranean vegetable cropping systems to manage root-knot nematodes. Description of the subject. A system approach based on co-design and experimental field evaluation of cropping systems (CSs), combining technical and varietal innovations, has been implemented for sustainable management of root-knot nematodes (RKN) in Mediterranean sheltered vegetable systems. Objectives. Cropping systems combining genetic resistance and cultural practices (crop rotations including susceptible, resistant, and non-host plants; intercropping management with nematicidal cover crops or soil solarization) were assessed over a period of 4 years (i) to reduce RKN populations and increase the durability of varietal resistances, (ii) to study the impact of these systems on soil ecology (plant-parasitic and free-living nematode communities), and (iii) to evaluate their acceptability by farmers. Method. Three CS prototypes, resulting from a co-design process with research and development stakeholders, were compared with CSs conventionally implemented in the Mediterranean region. The three prototypes were also evaluated using complementary methods: (i) system experiments in three commercial farms in Southern France; (ii) analytical experiments to decipher the mechanisms of action for some [agroecological??] levers; (iii) surveys to evaluate the acceptability of the prototypes by farmers. Results. All three CSs were found to be effective (90% RKN decrease, protection of partially resistant Solanaceae, no negative effect on non-phytoparasitic nematodes) and sustainable, when application conditions and soil biological equilibrium were favorable (global soil nematofauna diversified and abundant). The acceptability of the three systems depended on the type of farm where they were implemented and the attitude of the farmers towards innovation. Conclusions. These three CSs still need to be improved, in terms of their efficiency, in consultation with participating farmers, by introducing new agroecological levers, as well as innovation costs. Future research will also need to open up to a more comprehensive management of soil health.

Etude de trois souches d'Arthrobotrys oligospora : Caractérisation biologique et effets sur Meloidogyne mayaguensis parasite de la tomate au Sénégal. Three strains (ORS 18690 S2, ORS 18691 S6 and ORS 18693 S5) of the nematophagous fungus Arthrobotrys oligospora have been isolated in Senegal for the first time. In vitro, two strains (ORS 18690 S2 and ORS 18693 S5) of them trapped 100 % and the other (ORS 18691 S5) 80 %> of 7-day-old juvenile Meloidogyne mayaguensis within 48h. Optimal growth occured at 25-30°C and at a pH 5.6, but salinity inhibited development. In order to test the ability of fungi to control M. mayaguensis in pots on tomato, the fungus was incorporated into compost blocks or in vermiculite before sowing or subsequent transplanting. In pot experiments both strains reduced nematode populations ans stimulated seedling growth. However, these effects were higher in compost blocks than in vermiculite.

Various factors affecting the yield and viability of Pinus pinaster Ait. cotyledon protoplasts and the mitotic activity of regenerated cells are described. A study of the effect of sterilization procedures of the plant material showed that whereas the organs collected from disinfested seedlings allow for good yield and viability of isolated protoplasts, germination under non-sterile conditions favours a greater germinating capacity and stronger mitotic activity. Numerous clusters of from 10 to 15 cells were formed after 20 days of culture when a 5% aqueous solution of calcium hypochlorite was used as a sterilizing agent. The effects of an additional purification of the enzymes showed that although yield and viability of the protoplasts are only slightly improved, the more highly purified enzymes on the other band enhanced the mitotic activity markedly. Between the two total enzyme concentrations used (0.2 and 0.4%, and in which the relative ratio of each element was unchanged), only the lowest level supplied a debris-free protoplast suspension; mitotic activity occurred only in that case. Comparison of the populations of cotyledon protoplasts collected from seedlings at two different growth stages (not fully-developed or fully-expanded cotyledons) did not reveal any appreciable difference in their size distribution. Neither was the extent of cellular viability affected by the degree of cell differentiation at the time of collecting. On the other hand, the yield of protoplasts and the mitotic activity of the regenerated cells were greater when partially-developed organs were used. Moreover, a pretreatment of the elongating cotyledons with a mineral (half-strength MS macronutrients and full-strength micronutrients) and hormonal (15 μM BAP, 0.5 μM NAA) solution improved cell division frequency. [ABSTRACT FROM AUTHOR]

Adventitious budding can be induced on two types of Pinus pinaster Ait. organs. Cotyledons (10‐mm‐long), derived from 8 to 10‐day‐old seedlings, show morpho‐genetic response when an appropriate mineral solution is used (NH4+/K+= 1). Of the various cytokinin concentrations added to this optimal mineral medium, 0.8 μM BAP (6‐benzylaminopurine), with 5 nM NAA (1‐naphtaleneacetic acid), promoted organogenesis best. Buds were induced from outer mesophyll layers. Short shoots and the elongating needles (70‐mm‐long) were collected from cuttings of a mature tree (10‐years‐old). These cuttings benefited from physiological advantages of a well‐developed root system (by heating the substrate). In order to stimulate in vitro organogenesis, they had been sprayed every week from March to May with 10 μM BAP. When cultivated in the presence of 10 μM BAP and 25 nM NAA, 79% of the explants produced buds from dome‐shaped meristematic cell clusters that pre‐existed at the top of the short shoots. Moreover, among these, 42% gave rise to adventitious buds induced from proliferating mesophyll cells at the needle base. The morphologies of the two kinds of shoots were similar. Adventitious budding on these two different explants should allow vegetative multiplication of selected seedlings and elite trees. [ABSTRACT FROM AUTHOR]

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 .

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.

Background: Plant-parasitic nematodes (PPN) are major crop pests. On olive (Olea europaea), they significantly contribute to economic losses in the top-ten olive producing countries in the world especially in nurseries and under cropping intensification. The diversity and the structure of PPN communities respond to environmental and anthropogenic forces. The olive tree is a good host plant model to understand the impact of such forces on PPN diversity since it grows according to different modalities (wild, feral and cultivated olives). A wide soil survey was conducted in several olive-growing regions in Morocco. The taxonomical and the functional diversity as well as the structures of PPN communities were described and then compared between non-cultivated (wild and feral forms) and cultivated (traditional and high-density olive cultivation) olives., Results: A high diversity of PPN with the detection of 117 species and 47 genera was revealed. Some taxa were recorded for the first time on olive trees worldwide and new species were also identified. Anthropogenic factors (wild vs cultivated conditions) strongly impacted the PPN diversity and the functional composition of communities because the species richness, the local diversity and the evenness of communities significantly decreased and the abundance of nematodes significantly increased in high-density conditions. Furthermore, these conditions exhibited many more obligate and colonizer PPN and less persister PPN compared to non-cultivated conditions. Taxonomical structures of communities were also impacted: genera such as Xiphinema spp. and Heterodera spp. were dominant in wild olive, whereas harmful taxa such as Meloidogyne spp. were especially enhanced in high-density orchards., Conclusions: Olive anthropogenic practices reduce the PPN diversity in communities and lead to changes of the community structures with the development of some damaging nematodes. The study underlined the PPN diversity as a relevant indicator to assess community pathogenicity. That could be taken into account in order to design control strategies based on community rearrangements and interactions between species instead of reducing the most pathogenic species.

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., (Copyright © 2014 Académie des sciences. Published by Elsevier SAS. All rights reserved.)

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., (Copyright © 2014 Académie des sciences. Published by Elsevier SAS. All rights reserved.)

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.

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.