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Background Understanding the effects of resistance QTL on pathogen development cycle is an important issue for the creation of QTL combination strategies to durably increase disease resistance in plants. The oomycete pathogen Aphanomyces euteiches, causing root rot disease, is one of the major factors limiting the pea crop in the main producing countries. No commercial resistant varieties are currently available in Europe. Resistance alleles at seven main QTL were recently identified and introgressed into pea agronomic lines, resulting in the creation of Near Isogenic Lines (NILs) at the QTL. This study aimed to determine the effect of main A. euteiches resistance QTL in NILs on different steps of the pathogen life cycle. Results NILs carrying resistance alleles at main QTL in susceptible genetic backgrounds were evaluated in a destructive test under controlled conditions. The development of root rot disease severity and pathogen DNA levels in the roots was measured during ten days after inoculation. Significant effects of several resistance alleles at the two major QTL Ae-Ps7.6 and Ae-Ps4.5 were observed on symptom appearance and root colonization by A. euteiches. Some resistance alleles at three other minor-effect QTL (Ae-Ps2.2, Ae-Ps3.1 and Ae-Ps5.1) significantly decreased root colonization. The combination of resistance alleles at two or three QTL including the major QTL Ae-Ps7.6 (Ae-Ps5.1/Ae-Ps7.6 or Ae-Ps2.2/Ae-Ps3.1/Ae-Ps7.6) had an increased effect on delaying symptom appearance and/or slowing down root colonization by A. euteiches and on plant resistance levels, compared to the effects of individual or no resistance alleles. Conclusions This study demonstrated the effects of single or multiple resistance QTL on delaying symptom appearance and/or slowing down colonization by A. euteiches in pea roots, using original plant material and a precise pathogen quantification method. Our findings suggest that single resistance QTL can act on multiple or specific steps of the disease development cycle and that their actions could be pyramided to increase partial resistance in future pea varieties. Further studies are needed to investigate QTL effects on different steps of the pathogen life cycle, as well as the efficiency and durability of pyramiding strategies using QTL which appear to act on the same stage of the pathogen cycle. Electronic supplementary material The online version of this article (doi:10.1186/s12870-016-0822-4) contains supplementary material, which is available to authorized users.

Effects of NILs carrying single or combined resistance on variables of the Aphanomyces root rot development cycle. A-C/ Single QTL NIL experiment #1; D/ Combined and single QTL NIL experiment #4; E/ Single QTL NIL experiment #2. The first graph represents the evolution of the probability of symptom appearance for seven days after inoculation, for each line. It corresponds to the percentage of plants with symptoms per block for each scoring day. The second graph shows for each line the root colonization speed, corresponding to the slope of the curve of pathogen DNA amounts per block, until 10 days after inoculation, from 104 DNA copies detected. Pathogen DNA data was used from one biological replicate at the fourth day in experiments #1 and #2 and the seventh day in experiment #4. In the third graph, the AUDPC was calculated from the pathogen DNA quantification data over the ten days after inoculation. Bars represent standard errors. Attribution of each line to LSMeans group(s) is indicated by letter(s), according to the Tukey test (P

DS scores probability in each NIL set at each scoring day. A Experiments #1 and #2; B Experiments #3 and #4. The colors in each bar represent the probabilities of scores “0” (healthy plant) to “5” (dead plant), according to the DS rating scale used [25]. At two and three days after inoculation, no DS scores probability could be calculated from the CLMM model because some lines did not have symptoms. (PDF 1351 kb)

Les nappes d'eau souterraine constituent des ressources vulnérables que l'activité industrielle croissante contribue à polluer trop fréquemment. Les produits les plus manipulés se voient donc directement concernés dans les cas de pollution d'aquifères. A ce titre, les produits pétroliers, notamment ceux que l'on considère comme étant domestiques (gazole, fuel, essence, etc.) se situent au premier rang.Dans le but de mieux aborder ce type de contamination, des études sont menées sur un site expérimental de grandes dimensions et parfaitement contrôlé, dans lequel 476 l de gazole routier (GOR86) ont été déversés. Une première tentative de récupération du polluant, par infiltration de tensioactifs depuis la surface, démontre la capacité du mélange utilisé à mobiliser le polluant mais conduit à la réduction de la perméabilité du milieu poreux faisant ainsi apparaître une limitation des performances pour ce type de procédés de décontamination.Des expériences au laboratoire, conduites sur des colonnes de milieu poreux, ont été entreprises pour rechercher les causes de cette perte de conductivité hydraulique. Avec le sable considéré ici, les argiles ne jouent pas un rôle prépondérant dans le colmatage. Il est démontré également que le gradient de charge, quand il est augmenté, permet d'injecter une quantité plus importante de tensioactifs sans pour autant pallier ce problème de colmatage. Enfin, il apparaît que les tensioactifs, en présence des ions calcium, peuvent s'agglomérer pour former des associations de micelles lamellaires, cylindriques et/ou mixtes, assez volumineux pour être filtrés à la surface du sol à traiter. Au bout d'un certain temps, le milieu poreux est totalement colmaté et par conséquent le débit d'infiltration de la solution devient nul. Sur le plan de la récupération du polluant, ce paramètre s'avère être particulièrement important. Sa variation influence donc fortement les quantités de polluant mobilisé.Cette étude démontre la faisabilité du procédé. Toutefois elle souligne aussi que, sous peine de perdre de leur efficacité, les solutions de tensioactifs doivent conserver leurs caractéristiques initiales (stabilité de la taille des particules colloïdales notamment) pendant toute la durée du traitement. Dans la mesure où l'agglomération des micelles est en cause, il faudra rechercher les moyens d'obtenir une dispersion plus stable, par exemple par addition d'agents solvants., In case of groundwater contamination by hydrocarbon spills, one of the main problems is how to recover residual hydrocarbons trapped in the porous medium, forming a long term pollution source. In order to develop a better approach to such problems, experiments were conducted in a large experimental controlled site, called SCERES (Site Contrôlé Expérimental de Recherche pour la Réhabilitation des Eaux et des Sols) made of an impervious concrete basin (25 m x 12 m x 3 m) packed with two layers of quartz sand and fitted with specific instrumentation.This research site was experimentally polluted with diesel oil (476 litres), then the shape of the impregnation body was identified and oil saturation values were quantified thanks to a specific coring programme before and after each step of the experiments (water table fluctuations, hydraulic pumping, surfactant infiltration, etc.). The principle of the remediation technique is based on a surfactant flushing from the soil surface. This process was carried out when all of the removable diesel oil had been recovered by hydraulic pumping in the central recovery well. The surfactant infiltration allowed a displacement of the main part of the residual pollutant in the vertical zone of the impregnation body, in spite of a progressive reduction of hydraulic conductivity leading to a plugging of the porous matrix. This phenomenon has been observed by many scientists (Allred et Brown, 1994 ; Celik et al., 1982) and explained as being caused by a precipitation of the anionic surfactant in presence of calcium ions.This decrease of hydraulic conductivity, due to surfactant infiltration and its effects, was studied in the laboratory by the implementation of experiments using columns filled with the same sand as in the SCERES basin. The results showed that the reduction of the hydraulic conductivity of the porous medium cannot be due to the precipitation of the anionic surfactants in presence of calcium ions of the sand. If this were situation, all the porous medium in the column would have exhibited this loss of hydraulic conductivity. In our case, only the upstream part of the physical model was influenced by this phenomenon. Furthermore, the sand devoid of its clay minerals has nearly the same behaviour as a natural sand, with respect to the infiltration flowrate of the surfactants. This proves that the clay minerals, present in small proportion in this matrix, are not mainly responsible for the plugging problem. The influence of the hydraulic gradient, another studied parameter, was observed and permitted to apprehend the behaviour of the surfactant solution during its infiltration through the porous medium. . The increase of this parameter, even if it allows the injection of more surfactant, could not resolve the problem of the reduction of hydraulic conductivity. Finally, all the experiments indicated that the plugging effect (cancellation of the flowrate) happened after nearly 20 hours of surfactant infiltration through the porous matrix. The time parameter seems to be important since its variation can influence the stability of the surfactant solution. The results indicated that we can infiltrate a greater volume of the solution if it has been recently prepared. In other words, this is certainly due to the time necessary for the formation of liquid crystals obtained in presence of the calcium ions in the water used for the preparation of the solutions (tap water). After nearly 20 hours these crystals should have attained a size sufficient to be retained by a filtration effect, near the soil surface. We suggest that this filtration is the major factor responsible for the reduction of hydraulic conductivity and the plugging.The present study shows the feasibility of this process and it highlights the need to conserve the initial characteristics of the surfactants (especially the size stability of the colloidal particles) during all the treatment. Because of the agglomeration of the micelles, we have to search for means to ensure a good dispersion in the aqueous medium, for example by adding a solvent agent.

Il est generalement admis que les solutions micellaires les plus efficaces pour la recuperation du petrole sont celles qui conduisent a des tensions interfaciales basses au contact des fluides en place dans le gisement et qui, en meme temps, necessitent un minimum de produits amphiphiles pour former des microemulsions. Cette derniere propriete, d'ailleurs liee a la premiere, est importante pour des raisons economiques. Le propos de cet article est d'attirer l'attention surles principaux parametres qui gouvernent la formation des microemulsions, d'identifier leur importance relative et de les optimiser. Une condition optimale est definie, pour laquelle la quantite de tensio-actif necessaire pour former une microemulsion a partir de poids egaux d'hydrocarbure et de saumure est minimale. II existe une valeur optimale pour chacun des principaux parametres (masse moleculaire de l'hydrocarbure et des composes amphiphiles, rapport tensio-actif/ cosolvant, salinite et temperature), voleur qui correspond a un equilibre entre les ten-dances hydrophile et hydrophobe de la molecule de tensio-actif dans un systeme donne. Cet equilibre est confirme par des mesures de tension interfaciale et de coefficient de repartition du tensio-actif. Une relation entre les divers parametres est ainsi mise en evidence, qui peut aider a l'etablissement de formulations plus economiques. En particulier, des exemples sont donnes pour des applications a temperature elevee et forte concentration en sel.

In this work, salt, alcohol and surfactant effects are investigated, at different water-to-oil ratios to determine their influence on phase behavior. A linear relationship is found between the logarithm of water-oil ratio in the middle phase and the salinity. Moreover, in the middle of the range of salt or alcohol concentration giving a three-phase system, the water-oil ratio in the middle phase has a value close to unity (value defined as an optimum), whatever the overall water-oil ratio may be.