Identification of Frankia strains in nodules by hybridization of polymerase chain reaction products with strain-specific oligonucleotide probes

A set of oligonucleotides has been developed to study the competitivity of two Frankia strains in the nodulation of the roots of two host plant species: Alnus glutinosa and Alnus incana. Two 20 mer-oligonucleotides, complementary to highly conserved sequences inside the nifH gene, were used as primers for the polymerase chain reaction (PCR) system in order to amplify microsymbiont DNA extracted from actinorhizae. PCR products were analyzed using two strain-specific 15-mer oligonucleotides identified in the amplified region. Hybridization data indicate that strain ACoN24d is more competitive than train ArI3 in the nodulation of both hosts.     

Habitat assessment and strategy for conservation of Senecio sarracenicus L. populations along the river Moselle in France, at the western limit of its distribution range

A survey undertaken in 2001 and 2002 along the river Moselle in France allowed to find the location of 25 places with the protected species Senecio sarracenicus L. Most of these places were located directly on natural riverbanks, but some also occurred, with lower populations, on riverbanks artificialized with rocks and on road embankments. Maintenance of this species, despite canalisation of a large part of the river in the 1970s, is due to its ruderal and competitive strategy, giving it resistance against habitat disturbances and against competition from most other species, except maybe highly invasive species and shrubs. Conservation of its populations will therefore require the protection of its natural habitats on riverbanks and the control of invasive species and shrub colonisation, but without grazing or cutting management.     

Premiers résultats de recherches sur la compétitivité des champignons ectomycorhiziens

Resumé Les premiers résultats d'un modèle expérimental visant à quantifier le comportement de différents champignons ectomycorhiziens sur différents sols sont décrits. Ils mettent en évidence que l'intensité de l'inoculation par une souche introduite est un facteur décisif pour la mycorhization par cette souche. La photopériode et le temps sont également très importants à prendre en compte pour la définition de la capacité d'accueil d'un sol. Les deux sols testés ont des comportements très différents. La microflore du sol n'est pas toujours l'obstacle principal à l'infection mycorhizienne et à son extension.

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First results of research on the competitivity of ectomycorrhizal fungi

Summary The first results of an experimental model for quantifying the behaviour of different ectomycorrhizal fungi on different soils are described. They show that the inoculation intensity of the introduced strain is a decisive factor for the mycorrhization by this strain. Photoperiod and time are very important too for the definition of the soil receptivity. The two tested soils have very different behaviours. The soil microflora is not always the main obstacle to the mycorrhizal infection and to its extension.