Influence de divers effecteurs sur le developpement de Botrytis cinerea en milieu synthétique: Définition d'un cycle conidien

Influence of various parameters upon the growth of Botrytis cinerea on synthetic medium:Definition of a conidian cycleThe growth of Botrytis cinerea from the germination of conidia to the emission of conidiophores appears as a conidian cycle. The length of this cycle is influenced by environmental factors as temperature and pH. Malic and tartaric acids are the most effective parameters , at concentrations of tartaric acid higher than 7 g/l the formation of conidiophores is not possible

Impacts of organic and conventional crop management on diversity and activity of free-living nitrogen fixing bacteria and total bacteria are subsidiary to temporal effects

A three year field study (2007-2009) of the diversity and numbers of the total and metabolically active free-living diazotophic bacteria and total bacterial communities in organic and conventionally managed agricultural soil was conducted at the Nafferton Factorial Systems Comparison (NFSC) study, in northeast England. The result demonstrated that there was no consistent effect of either organic or conventional soil management across the three years on the diversity or quantity of either diazotrophic or total bacterial communities. However, ordination analyses carried out on data from each individual year showed that factors associated with the different fertility management measures including availability of nitrogen species, organic carbon and pH, did exert significant effects on the structure of both diazotrophic and total bacterial communities. It appeared that the dominant drivers of qualitative and quantitative changes in both communities were annual and seasonal effects. Moreover, regression analyses showed activity of both communities was significantly affected by soil temperature and climatic conditions. The diazotrophic community showed no significant change in diversity across the three years, however, the total bacterial community significantly increased in diversity year on year. Diversity was always greatest during March for both diazotrophic and total bacterial communities. Quantitative analyses using qPCR of each community indicated that metabolically active diazotrophs were highest in year 1 but the population significantly declined in year 2 before recovering somewhat in the final year. The total bacterial population in contrast increased significantly each year. Seasonal effects were less consistent in this quantitative study

Développement de microorganismes dans le bois de cœur de chêne (Quercus petraea Liebl) au cours du séchage naturel à l'air libre

Development of microorganisms in the oak heartwood (Quercus petraea Liebl) during air drying in open air conditions. Different samples of oak heartwood Quercus petraea Liebl species were observed by scanning electron microscopy and transmission electron microscopy. We studied four durations of air drying (6, 12, 18 and 24 months) and different depths (0, 3, 5 and 10 mm). The photographs show a large colonisation of the wood surface by different spores during the first 6 months, but only a few of them are able to sprout and produce a mycelium. The mycelium is able to penetrate inside the wood by a fissure. After 12 months we note the presence of mycelium, in very limited numbers, in the spring vessels. From this point, the fungi are able to penetrate into the heartwood cell wall.Des échantillons de bois de chêne représentant différentes durées de séchage à l'air libre et différentes profondeurs dans la masse du bois sont étudiés en microscopie électronique à balayage et à transmission. On observe après 6 mois de séchage que la surface du bois se recouvre de spores dont un très faible pourcentage germent et forment un mycélium. Au bout de 12 mois, quelques mycélia atteignent les premiers millimètres du bois en pénétrant par des microfissures et gagnent les vaisseaux du bois de printemps. Les champigons ayant atteint les couches profondes se développent abondament dans la parois des cellules du bois de coeur