title: Successful nodulation of Casuarina by Frankia in axenic conditions.
abstract: OBJECTIVE
  In order to depict the fine interactions that lead to nodulation, absolute microbiological control of the symbiotic partners is required, i.e. the ability to obtain in vitro axenic nodulation, a condition that has never been fulfilled with the Casuarina-Frankia symbiosis. The effects of culture conditions on plant growth and nodule formation by Casuarina cunninghamiana were investigated.
  
  
  RESULTS
  Axenic (capped tubes with different substrates), and nonaxenic cultures (Gibson tubes, pot cultures) were tested. In axenic conditions, C. cunninghamiana, inoculated with Frankia, had poor growth and did not form nodules at 6 weeks. Plants cultivated in Gibson tubes reached the four axillary shoots stage within 6 weeks and formed nodules 4 weeks after inoculation. Sand-pot cultures allowed us to relate the plant development stage at inoculation with nodulation.
  
  
  CONCLUSIONS
  The sterile replacement of the cap by a plastic bag increased plant growth and enabled nodule formation 6 weeks after inoculation. The new system of plant culture allows the axenic nodule formation 6 weeks after inoculation. Nodulation behaviour is related to plant development and confinement.
  
  
  CONCLUSIONS
  This axenic plant nodulation system is of major interest in analysing the roles of Frankia genes in nodulation pathways.
authors.affiliation: Département de Biologie, Faculté des Sciences, Université Mohammed V-Agdal, Rabat, Morocco.
authors.forename: H
authors.initials: H
authors.lastname: Echbab
authors.forename: M
authors.initials: M
authors.lastname: Arahou
authors.forename: M
authors.initials: M
authors.lastname: Ducousso
authors.forename: S
authors.initials: S
authors.lastname: Nourissier-Mountou
authors.forename: R
authors.initials: R
authors.lastname: Duponnois
authors.forename: H
authors.initials: H
authors.lastname: Lahlou
authors.forename: Y
authors.initials: Y
authors.lastname: Prin
mesh_terms: D001315:Australia; D040161:Frankia / Q000502:physiology*; D019684:Magnoliopsida / Q000382:microbiology*; D009172:Mycology / Q000379:methods; D009586:Nitrogen Fixation; D018517:Plant Roots / Q000382:microbiology; D012988:Soil Microbiology; D013559:Symbiosis; D014197:Trees / Q000382:microbiology*; D014329:Tropical Climate