Isolation of Bacteria with Antifungal Activity against the Phytopathogenic Fungi Stenocarpella maydis and Stenocarpella macrospora

Stenocarpella maydis and Stenocarpella macrospora are the causal agents of ear rot in corn, which is one of the most destructive diseases in this crop worldwide. These fungi are important mycotoxin producers that cause different pathologies in farmed animals and represent an important risk for humans. In this work, 160 strains were isolated from soil of corn crops of which 10 showed antifungal activity against these phytopathogens, which, were identified as: Bacillus subtilis, Pseudomonas spp., Pseudomonas fluorescens, and Pantoea agglomerans by sequencing of 16S rRNA gene and the phylogenetic analysis. From cultures of each strain, extracellular filtrates were obtained and assayed to determine antifungal activity. The best filtrates were obtained in the stationary phase of B. subtilis cultures that were stable to the temperature and extreme pH values; in addition they did not show a cytotoxicity effect against brine shrimp and inhibited germination of conidia. The bacteria described in this work have the potential to be used in the control of white ear rot disease

Combined field inoculations of pseudomonas bacteria, arbuscular mycorrhizal fungi, and entomopathogenic nematodes and their effects on wheat performance

In agricultural ecosystems, pest insects, pathogens, and reduced soil fertility pose major challenges to crop productivity and are responsible for significant yield losses worldwide. Management of belowground pests and diseases remains particularly challenging due to the complex nature of the soil and the limited reach of conventional agrochemicals. Boosting the presence of beneficial rhizosphere organisms is a potentially sustainable alternative and may help to optimize crop health and productivity. Field application of single beneficial soil organisms has shown satisfactory results under optimal conditions. This might be further enhanced by combining multiple beneficial soil organisms, but this remains poorly investigated. Here, we inoculated wheat plots with combinations of three beneficial soil organisms that have different rhizosphere functions and studied their effects on crop performance. Plant beneficial Pseudomonas bacteria, arbuscular mycorrhizal fungi (AMF), and entomopathogenic nematodes (EPN), were inoculated individually or in combinations at seeding, and their effects on plant performance were evaluated throughout the season. We used traditional and molecular identification tools to monitor their persistence over the cropping season in augmented and control treatments, and to estimate the possible displacement of native populations. In three separate trials, beneficial soil organisms were successfully introduced into the native populations and readily survived the field conditions. Various Pseudornonas, mycorrhiza, and nematode treatments improved plant health and productivity, while their combinations provided no significant additive or synergistic benefits compared to when applied alone. EPN application temporarily displaced some of the native EPN, but had no significant long-term effect on the associated food web. The strongest positive effect on wheat survival was observed for Pseudomonas and AMF during a season with heavy natural infestation by the frit fly, Oscinella frit, a major pest of cereals. Hence, beneficial impacts differed between the beneficial soil organisms and were most evident for plants under biotic stress. Overall, our findings indicate that in wheat production under the test conditions the three beneficial soil organisms can establish nicely and are compatible, but their combined application provides no additional benefits. Further studies are required, also in other cropping systems, to fine-tune the functional interactions among beneficial soil organisms, crops, and the environment

Breeding for increased nitrogen-use efficiency: a review for wheat (T. aestivum L.)

Nitrogen fertilizer is the most used nutrient source in modern agriculture and represents significant environmental and production costs. In the meantime, the demand for grain increases and production per area has to increase as new cultivated areas are scarce. In this context, breeding for an efficient use of nitrogen became a major objective. In wheat, nitrogen is required to maintain a photosynthetically active canopy ensuring grain yield and to produce grain storage proteins that are generally needed to maintain a high end-use quality. This review presents current knowledge of physiological, metabolic and genetic factors influencing nitrogen uptake and utilization in the context of different nitrogen management systems. This includes the role of root system and its interactions with microorganisms, nitrate assimilation and its relationship with photosynthesis as postanthesis remobilization and nitrogen partitioning. Regarding nitrogen-use efficiency complexity, several physiological avenues for increasing it were discussed and their phenotyping methods were reviewed. Phenotypic and molecular breeding strategies were also reviewed and discussed regarding nitrogen regimes and genetic diversity

Compatibility between the plant growth-promoting rhizobacteria Azospirillum and Pseudomonas on roots

Plant Growth-Promoting Rhizobacteria (PGPR) can form an associative symbiosis with plants, which results in stimulation of plant growth. PGPR harbour different phytobeneficial mechanisms (non-symbiotic nitrogen fixation, phytohormone synthesis, etc.). Various PGPR can interact with the same host plant, and it is possible that their phytobeneficial effects will be influenced by the interactions between these PGPR. The objective of this doctoral work was to characterize PGPR compatibility in the rhizosphere of the same host plant, in the case of model bacteria belonging to the genera Azospirillum and Pseudomonas. Because certain phytobeneficial Pseudomonas produce antimicrobial metabolites, such as 2,4-diacetylphloroglucinol (DAPG), we have first examined if DAPG production capacity could be involved in Azospirillum inhibition. In vivo experiments, performed with P. fluorescens F113 and a DAPG-negative mutant in gnotobiotic systems, showed that root colonization and phytostimulation activity of certain Azospirillum PGPR was indeed affected in the presence of DAPG-producing Pseudomonas. In order to evaluate Azospirillum root colonization in non-sterile soil, real-time quantitative PCR tools were developed and validated for three prominent Azospirillum strains (A. lipoferum CRT1, A. brasilense UAP-154 and CFN-535). The use of these real-time PCR tools enabled the comparison of the three Azospirillum strains, each co-inoculated with the DAPG-producing strain P. fluorescens F113, in the rhizosphere of maize grown in non-sterile soil. Root colonization levels differed according to the Azospirillum strain, and the combination of phytobeneficial microorganisms led to enhanced maize growth in comparison with non-inoculated plants. These results suggest that PGPR belonging to the genera Pseudomonas and Azospirillum may be compatible in the rhizosphere of a same plant, even if the former have the potential to inhibit some of the latter by producing antimicrobial secondary metabolitesLes bactéries rhizosphériques qualifiées de PGPR (Plant Growth-Promoting Rhizobacteria) forment des symbioses associatives avec les plantes, stimulant la croissance de ces dernières. Les PGPR présentent différents mécanismes phytobénéfiques (production de phytohormones, fixation non symbiotique de l'azote, etc.). Plusieurs PGPR sont susceptibles d'interagir avec la même plante hôte, et il est possible que leurs effets phytobénéfiques soient influencés par les interactions qu'elles auront les unes avec les autres. L'objectif de cette thèse était de caractériser la compatibilité des PGPR dans la rhizosphère d'une même plante hôte, dans le cas de modèles bactériens appartenant aux genres Azospirillum et Pseudomonas. Certains Pseudomonas phytobénéfiques produisant des métabolites antimicrobiens, comme le 2,4-diacétylphloroglucinol (DAPG), nous avons tout d'abord examiné si la capacité à produire du DAPG pouvait inhiber Azospirillum. Les expériences de confrontation réalisées in vivo avec P. fluorescens F113 et un mutant DAPG-négatif, en système gnotobiotique, ont montré que la colonisation racinaire et l'activité phytostimulatrice de certaines PGPR Azospirillum pouvaient effectivement être diminuées en présence de Pseudomonas producteurs de DAPG. Pour évaluer la colonisation racinaire par Azospirillum en sol non stérile, des outils de PCR quantitative en temps réel ont été développés et validés pour trois souches de premier plan (A. lipoferum CRT1, A. brasilense UAP-154 et CFN-535). L'utilisation de ces outils a permis la comparaison de ces trois souches d'Azospirillum, chacune co-inoculée avec la souche P. fluorescens F113 productrice de DAPG, sur du maïs cultivé en sol non stérile. Les niveaux de colonisation racinaire différaient selon la souche d'Azospirillum, et la combinaison de microorganismes phytobénéfiques conduisait à une meilleure croissance du maïs par comparaison avec des plantes non inoculées. Les résultats suggèrent que des PGPR des genres Pseudomonas et Azospirillum peuvent être compatibles dans la rhizosphère d'une même plante, même si les premiers ont le potentiel d'inhiber certains des seconds par la production de métabolites secondaires antimicrobien

Une liberté singulière et plurielle : la liberté publique de l'enseignement privé

International audienc

Effets de deux sources lumineuses sur la croissance et sur le contenu glucidique et gibbérellinique des feuilles de Cichorium intybus L cultivé in vitro

Des plantules de Cichorium intybus L (cv Flash) cultivées in vitro sont exposées à la lumière fournie soit par des lampes Cool-White, soit par des lampes Gro-Lux. Le développement du feuillage, de même que son contenu en gibbérellines et en glucides alcoolo-solubles sont modifiés par le type d'éclairement. Les lampes Cool-White permettent d'obtenir des feuilles plus grandes et plus riches en gibbérellines. Sous lumière Gro-Lux, les limbes qui contiennent davantage de glucides sont toujours moins développés.Effects of two illumination sources on growth and on carbohydrate and gibberellin leaf contents of in vitro grown Cichorium intybus L. Fourteen-d old seedlings of Cichorium intybus L (cv Flash) were grown in vitro under a 16-h photoperiod (15 ± 1 W m-2 ). Two different spectral emissions (fig 1) were obtained by using Cool-White and Gro-Lux fluorescent lamps. Differences in the growth (table I), of gibberellin (fig 2) and carbohydrate (table II) contents of leaves were observed. Plantlets grown under Cool-White lamps developed larger leaves with a high level of gibberellin-like activity. Carbohydrate content increased in the Gro-Lux illuminated leaves

Le Bleu de Gex, une petite production pour un grand fromage

Le fromage le plus connu du massif jurassien est bien sûr le Comté, avec ses 46 000 tonnes de production. sa présence sur l'ensemble du massif, sa commercialisation à large échelle. Nous parlerons ici d'un autre fromage fabriqué en Franche-Comté et qui fait un peu figure de lilliputien : la production annuelle de Bleu de Gex. appelé aussi Bleu du Haut-Jura ou Bleu de Septmoncel. se situe en effet depuis 25 ans entre 500 et 600 tonnes. Il s'agit de la plus petite AOC fromagère au lait de vache en France