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The foxglove aphid, Aulacorthum solani (Kaltenbach) (Hemiptera: Aphididae), and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), are among the serious insect pests found in greenhouses. The efficacy of microbial control against these insects has been demonstrated and can be enhanced by the combination of different microbial agents. This study evaluated the efficacy of Bacillus pumilus Meyer and Gottheil PTB180 and Bacillus subtilis (Ehrenberg) Cohn PTB185, used alone and together, to control these two aphids both in the laboratory and in greenhouse on tomato, Solanum lycopersicum Linnaeus (Solanaceae), and cucumber, Cucumis sativus Linnaeus (Cucurbitaceae), plants. The results from the laboratory tests showed an increase in mortality induced by all biological treatments. In the greenhouse, all treatments induced mortality rates significantly higher than that of the control for A. solani. Similarly, all treatments performed better than the control against A. gossypii, significantly reducing its reproduction. Furthermore, we found no additive effects when mixing products nor negative interactions affecting survival for the bacteria investigated. These microorganisms therefore have potential for use in biological control., Les pucerons de la digitale, Aulacorthum solani (Kaltenbach) (Hemiptera : Aphididae), et du melon, Aphis gossypii Glover (Hemiptera : Aphididae), font partie des ravageurs les plus nuisibles en serres. L’efficacité de la lutte microbienne contre ces insectes a été démontrée et pourrait être améliorée par la combinaison de différents agents microbiens. Cette étude a évalué l’efficacité de Bacillus pumilus Meyer and Gottheil PTB180 et Bacillus subtilis (Ehrenberg) Cohn PTB185, utilisés seuls ou ensemble, pour lutter contre ces deux pucerons en laboratoire et en serre sur des plants de tomate, Solanum lycopersicum Linnaeus (Solanaceae), et de concombre, Cucumis sativus Linnaeus (Cucurbitaceae). En laboratoire, les résultats ont montré une augmentation de la mortalité induite par tous les traitements biologiques. En serres, pour A. solani, tous les traitements ont induit un taux de mortalité nettement supérieur au témoin. Tous les traitements ont aussi significativement réduit la reproduction de A. gossypii. De plus, nous ne montrons aucun effet additif lors du mélange des produits ni aucune interaction négative affectant la survie des bactéries. Ces microorganismes ont donc un potentiel intéressant pour la lutte biologique.

The foxglove aphid, Aulacorthum solani (Kaltenbach) (Hemiptera: Aphididae), and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), are among the serious insect pests found in greenhouses. The efficacy of microbial control against these insects has been demonstrated and can be enhanced by the combination of different microbial agents. This study evaluated the efficacy of Bacillus pumilus Meyer and Gottheil PTB180 and Bacillus subtilis (Ehrenberg) Cohn PTB185, used alone and together, to control these two aphids both in the laboratory and in greenhouse on tomato, Solanum lycopersicum Linnaeus (Solanaceae), and cucumber, Cucumis sativus Linnaeus (Cucurbitaceae), plants. The results from the laboratory tests showed an increase in mortality induced by all biological treatments. In the greenhouse, all treatments induced mortality rates significantly higher than that of the control for A. solani. Similarly, all treatments performed better than the control against A. gossypii, significantly reducing its reproduction. Furthermore, we found no additive effects when mixing products nor negative interactions affecting survival for the bacteria investigated. These microorganisms therefore have potential for use in biological control., Les pucerons de la digitale, Aulacorthum solani (Kaltenbach) (Hemiptera : Aphididae), et du melon, Aphis gossypii Glover (Hemiptera : Aphididae), font partie des ravageurs les plus nuisibles en serres. L’efficacité de la lutte microbienne contre ces insectes a été démontrée et pourrait être améliorée par la combinaison de différents agents microbiens. Cette étude a évalué l’efficacité de Bacillus pumilus Meyer and Gottheil PTB180 et Bacillus subtilis (Ehrenberg) Cohn PTB185, utilisés seuls ou ensemble, pour lutter contre ces deux pucerons en laboratoire et en serre sur des plants de tomate, Solanum lycopersicum Linnaeus (Solanaceae), et de concombre, Cucumis sativus Linnaeus (Cucurbitaceae). En laboratoire, les résultats ont montré une augmentation de la mortalité induite par tous les traitements biologiques. En serres, pour A. solani, tous les traitements ont induit un taux de mortalité nettement supérieur au témoin. Tous les traitements ont aussi significativement réduit la reproduction de A. gossypii. De plus, nous ne montrons aucun effet additif lors du mélange des produits ni aucune interaction négative affectant la survie des bactéries. Ces microorganismes ont donc un potentiel intéressant pour la lutte biologique.

Composting fruit and vegetable waste from grocery stores on farms is a challenge due to the large quantity of liquid that leaches out. This leachate needs to be characterized for its effects on plant growth and soil. It was acidic with high conductivity; the plant mineral nutrient contents derived from the leachate (in decreasing order) were K, N mainly as ammonium-N, Ca, Mg, Na, and P; the trace elements were quite low. The germination and rootlet growth of cress and corn increased with the dilution of the compost leachate. In greenhouse assays, the compost leachate exhibited phytotoxicity to corn when used at high application rates. The corn leaf area, shoot and root biomass, plant concentrations and uptake of N, P and K were similar among the 20 mM N-fertilized control and the 30–40 m3/ha leachate treatments. In a field study on sandy loam, corn yields and plant uptake of P and K were similar among the mineral fertilized control and split-application leachate treatments applied to meet the P or K requirements of corn. After harvest, the soil pH, conductivity, and total N, P, and K contents were not affected by the leachate treatments. These results demonstrate the opportunity of recycling plant nutrients from compost leachate of fruit and vegetable waste as fertilizer to meet crop nutrient requirements without phytotoxicity and trace elements threats.

Composting fruit and vegetable waste from grocery stores on farms is a challenge due to the large quantity of liquid that leaches out. This leachate needs to be characterized for its effects on plant growth and soil. It was acidic with high conductivity; the plant mineral nutrient contents derived from the leachate (in decreasing order) were K, N mainly as ammonium-N, Ca, Mg, Na, and P; the trace elements were quite low. The germination and rootlet growth of cress and corn increased with the dilution of the compost leachate. In greenhouse assays, the compost leachate exhibited phytotoxicity to corn when used at high application rates. The corn leaf area, shoot and root biomass, plant concentrations and uptake of N, P and K were similar among the 20 mM N-fertilized control and the 30–40 m3/ha leachate treatments. In a field study on sandy loam, corn yields and plant uptake of P and K were similar among the mineral fertilized control and split-application leachate treatments applied to meet the P or K requirements of corn. After harvest, the soil pH, conductivity, and total N, P, and K contents were not affected by the leachate treatments. These results demonstrate the opportunity of recycling plant nutrients from compost leachate of fruit and vegetable waste as fertilizer to meet crop nutrient requirements without phytotoxicity and trace elements threats.

Le but de ce travail était de déterminer comment l’amendement d’un substrat de serre avec différents taux de biochars influence l’activité biologique, la biomasse microbienne, l’émission des gaz à effet de serre et le rendement de la tomate et du poivron de serre. L’effet du biochar sur l’utilisation de l’eau et des engrais lors de la production de ces deux cultures a aussi été étudié. Dans ce travail quatre biochars ont été fabriqués à partir de saule et d’écorce d’érable soumis à des températures de pyrolyse variant de 400°C à 700°C. Un biochar vendu commercialement au Colorado, préparé à partir de pin à 700°C, a aussi été utilisé. Ces biochars ont été utilisés dans des études d’incubations en laboratoire, mais aussi en serre dans deux essais de production avec la tomate et le poivron., Faculté des sciences de l’agriculture et de l’alimentation de l’Université Laval

About 2–5% of rhizobacteria, when present in large number, are able to promote plant growth. Production of plant hormones and improving mineral nutrition are examples of direct promotion, while protecting plants against many diseases caused by bacteria, fungi, viruses, nematodes, or insects is indirect mechanism of growth promotion., 0

Untreated greenhouse effluents or leak solution constitute a major environmental burden because their nitrate and phosphate concentrations may induce eutrophication. Artificial wetlands may offer a low cost alternative treatment of greenhouse effluents and consequently improve the sustainability of greenhouse growing systems. The objectives of this study were to 1) characterize the efficiency of different types of wetland to reduce ion content of greenhouse tomato effluent, and 2) improve the wetland efficiency by adding carbon of 0-800 mg L-1 sucrose. Experiments were conducted at Laval University where 30 pilot scale horizontal subsurface flow artificial wetlands (0.81 m3) were built. Two types of aquatic macrophytes, Pragmites australis and Typha latifolia, and a control group without plants were tested. The hydraulic retention time was 10 days. During the study, EC of the greenhouse effluent ranged between 1.5 to 5.5 mS cm-1, while 0 to 800 mg L-1 of sucrose was provided to improve the biological activity of the wetland. The macro- and micro-elements, the greenhouse gases (CH4, CO2, N2O) and the population of bacteria were measured for each unit. At commercial scale, two vertical subsurface wetlands (43.2 m3) were installed at Ste-Sophie Québec, on the production site of Les Serres Nouvelles Cultures (Sagami). According to our results, 50-90% of nitrate (NO3-) and 40-100% of phosphate (PO43-) were removed from the effluent. At Laval University, artificial wetlands with Typha latifolia were more efficient than wetlands with Phragmites australis or without plants. Addition of sucrose increased wetlands’ microbial population and consequently reduced the mineral content of the wastewater, but increased significantly the emission of greenhouse gases. Results will further be discussed in terms of the best wetland design to treat greenhouse effluents, but also in terms of the environmental impact.

Forty-eight bacteria isolates from the rhizosphere of three cultivars of corn and three different soils were examined for their phosphate solubiling ability. The tests were realized on NBRIP (National Botanical Research Institute of Phosphate Growth medium) containing the Tilemsi phosphate rock (TPR) as the only source of insoluble phosphorus. All the isolates solubilized the TPR in solid and liquid media. Twenty isolates were selected for their high solubilizing capacity in liquid medium (105 to 311 mg P/ ml/g of TPR). These isolates were submitted to different stress conditions (acid medium with pH 7 to 5, five successive growths and the temperature range of 30°C to 45°C). Only six isolates (I 1 , I 2 , I 3 , I 4 I 5 ad I 6) were able to maintain their ability of solubilizing the TPR and also they were not antagonistics. These selected isolates were also tested for their solubilization efficiency (SE) of TPR and phytate on NBRIP solid medium containing the TPR and phytate as the only insoluble source of phosphorus and phytate respectively. The maximum solubilization (300%) for TPR was obtained with the isolate I 5 and 167% for phytate with the isolate I 1 . It has been observed that the bacteria isolates have an average solubilization capacity of 18.54 kg P 2 O 5 out off 30 kg contained in 100 kg of PNT. The same bacteria strains were tested for their plant growth promotion (PGPR) characteristics which indicated that all produced low molecular weight Organic Acids, Siderophores, Indole Acetic Acid (IAA or auxine), but none of them produced the Hydrocyanic Acid (HCN)., Résumé Quarante huit (48) souches de bactéries isolées de la rhizosphère de trois (3) variétés différentes de maïs et de sol ont été testées pour leur habilité à dissoudre les phosphates naturels. Les tests ont été réalisés sur le milieu de culture NBRIP (National Botanical Research Institute of Phosphate Growth medium) contenant du Phosphate Naturel de Tilemsi (PNT) comme seule source de phosphore insoluble. Tous les isolats ont solubilisé le PNT en milieux solide et liquide. Vingt (20) isolats ont été sélectionnés pour leur grande capacité de solubilisation en milieu liquide qui varie de 105 à 311 mg de P/ml/g de PNT. Ces isolats ont été soumis à différentes conditions de stress (milieux acides de pH 7, 6, et 5) ; 5 repiquages successifs et à des températures de 30°, 35°, 40° et 45°C). Seulement 6 souches bactéries (I 1 , I 2 , I 3 , I 4 , I 5 , I 6) étaient capables de maintenir leur capacité de solubilisation du PNT et elles n'étaient pas Isolation and biological characterization of phosphate solubilizing bacteria strains from the rhizospheric soils of corn in Mali L'isolement et la caractérisation biologique des souches de bactéries du sol rhizosphérique de maïs solubilisant le phosphate au Mali Cahiers de l'Economie Rurale n°12 71 – Isolation and biological characterization of phosphate solubilizing bacteria strains from the rhizospheric soils of corn in Mali antagonistes. Ces isolats sélectionnés ont été testés aussi pour leur efficacité de solubilisation (ES) du PNT et du phytate en milieu solide contenant du PNT et du phytate comme seules sources insolubles de phosphore. L'efficacité maximale de solubilisation du PNT (300 %) a été obtenue avec l'isolat I 5 et 167 % du phytate avec l'isolat I 1 . Il a été observé également que les isolats des souches bactériennes ont une capacité moyenne de dissolution de 18 kg de P 2 O 5 sur les 30 kg contenus dans 100 kg de PNT. Les mêmes souches bactériennes ont été testées pour leurs caractéristiques de production de sub

We investigated the in vitro influence of humic substances (HS) extracted from de-inking paper sludge compost on the inhibition of Pythium ultimum by two compost bacteria, Rhizobium radiobacter (Agrobacterium radiobacter) and Pseudomonas aeruginosa. When low concentrations (5 or 50 mgzl−1) of HS were added to the culture medium, fungal inhibition by R. radiobacter significantly increased (P < 0.01) by 2–3%. In contrast, these low levels of HS had no effect on P. ultimum inhibition by P. aeruginosa. The Fe, chelated by HS, was in part responsible for the decrease of P. ultimum inhibition by the bacteria when increasing amounts of HS were added in the culture medium. The addition of 500 mgl−1 of humic acids isolated from de-inking paper sludge compost or from fossil origin completely eliminated the inhibition of P. ultimum by R. radiobacter. This Fe effect also stimulated growth of R. radiobacter and reduced its siderophore production in a minimal medium supplemented with HS as sole source of Fe. The results showed that HS influence microbial antagonism when added to a culture medium. However, this effect varies with different factors such as the type of bacteria, concentration of HS, molecular weight and Fe content.

Phosphorus (P) is vital for plant growth. However, most added soluble P forms insoluble phosphates. Therefore, inorganic P (Pi) accumulates in soils. Soil organic P (Po) is another important reserve (20 to 80% of total soil P). To be available for plant Po must first be mineralized by soil microorganisms. The variability of the results of inoculation trials with P solubilizing microorganisms (PSMs) clearly reflects the complexity of the interactions occurring in the soil-plant-microbes-fauna ecosystem. Important points overlooked in previous studies will be presented and perspectives of the use of PSMs to allow the plant to benefit from soil reserves in Pi and Po will be discussed.

L’antagonisme de 49 souches de Rhizobium meliloti envers F. oxysporum a été étudié en cultures pures. On n’a pu démontré aucune corrélation significative entre l’efficacité symbiotique des souches et leur pouvoir d’antagonisme. Aucune souche de R. meliloti n’a produit de substances antibiotiques, Antagonism of 49 strains of Rhizobium meliloti towards F. orysporum was studied in pure cultures. No significant correlation was found between symbiotic effectiveness of the strains and their antagonistic ability. None of the strains of R. meliloti tested produced antibiot

Arctic Mesorhizobium sp. N33 isolated from nodules of Oxytropis arctobia in Canada’s eastern Arctic has a growth temperature range from 0°C to 30°C and is a well-known cold-adapted rhizobia. The key molecular mechanisms underlying cold adaptation in Arctic rhizobia remains totally unknown. Since the concentration and contents of metabolites are closely related to stress adaptation, we applied GC-MS and NMR to identify and quantify fatty acids and water soluble compounds possibly related to low temperature acclimation in strain N33. Bacterial cells were grown at three different growing temperatures (4°C, 10°C and 21°C). Cells from 21°C were also cold-exposed to 4°C for different times (2, 4, 8, 60 and 240 minutes). We identified that poly-unsaturated linoleic acids 18∶2 (9, 12) & 18∶2 (6, 9) were more abundant in cells growing at 4 or 10°C, than in cells cultivated at 21°C. The mono-unsaturated phospho/neutral fatty acids myristoleic acid 14∶1(11) were the most significantly overexpressed (45-fold) after 1hour of exposure to 4°C. As reported in the literature, these fatty acids play important roles in cold adaptability by supplying cell membrane fluidity, and by providing energy to cells. Analysis of water-soluble compounds revealed that isobutyrate, sarcosine, threonine and valine were more accumulated during exposure to 4°C. These metabolites might play a role in conferring cold acclimation to strain N33 at 4°C, probably by acting as cryoprotectants. Isobutyrate was highly upregulated (19.4-fold) during growth at 4°C, thus suggesting that this compound is a precursor for the cold-regulated fatty acids modification to low temperature adaptation.

A simple method is described for trapping phosphate solubilizing bacteria (PSB) strongly attached to the hyphae of the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis (Ri). Bacteria were isolated from the hyphosphere of mycorrhizal leek plants growing on Turface previously inoculated with soil suspensions, obtained from the mycorrhizosphere of mycorrhizal plants growing in agricultural settings or maple forests in Quebec, Canada. Among the best PSB strongly attached to the hyphae of Ri, 26 isolates belonged to Burkholderia spp. and one was identified as Rhizobium miluonense. Four hyphobacteria exhibiting high potential of inorganic and organic P mobilization were further compared with four equivalent mycorrhizobacteria directly isolated from mycorrhizospheric soils sampled. In general, hyphobacteria were superior in mobilizing P from hydroxyapatite and from a low reactivity igneous phosphate rock from Quebec. Release of gluconic acid or the product of its oxidation 2-ketogluconic acid, are the main mechanisms involved in P solubilization. In a two compartments Petri plate system, Ri extraradical hyphal exudates, supported PSB growth and activity. In the absence of PSB Ri showed a negligible P solubilization activity. In the presence of PSB a substantial increase in P mobilization was observed, and the superiority of hyphobacterial activity was also observed under this system. Our results suggest that in developing a bioinoculant based on selected PSB, their interaction with AMF hyphae should not be overlooked.