Abundance of Frankia from Gymnostoma spp. in the rhizosphere of Alphitonia neocaledonica, a non-nodulated Rhamnaceae endemic to New Caledonia | [Abondance de Frankia provenant de Gymnostoma spp. dans la rhizosphere d'Alphitonia neocaledonica, Rhamnaceae non nodulee endemique en Nouvelle Caledonie]
2000
Gauthier, G. (Institut National de la Recherche Agronomique, Montpellier (France). Centre de Montpellier, Symbioses Tropicales et Mediterraneennes) | Jaffre, T. | Prin, Y.
The capacity of different soils of New Caledonia to induce nodulation in Gymnostoma poissonianum was studied. The soils were sampled under five Gymnostoma species, Alphitonia neocaledonica (a non-nodulated endemic Rhamnaceae) and Pinus caribea (an introduced species) growing in various ecological conditions. Using G. poissonianum as trap-host it was observed a higher abundance of Frankia from Gymnostoma spp. in the rhizosphere of A. neocaledonica as compared with bare soils and P. caribea rhizosphere. The nodulating capacity of A. neocaledonica rhizosphere was almost similar to that of the five Gymnostoma species (symbiotic host) studied in the same stations. In comparison, bare soils or rhizosphere of P. caribea had poor nodulating capacities. It was isolated 14 Frankia strains from nodules of G. poissonianum after baiting with the rhizospheric soils of five Gymnostoma and A. neocaledonica. Using the PCR/RFLP method, it was confirmed the similarity with those already described. Frankia was abundant in the rhizosphere of A. neocaledonica in all the sites studied. One explanation could be a positive tropism of Frankia towards species belonging to families having nodulated species, which is the case of A. neocaledonica endemic in New Caledonia. It can be supposed that the non-nodulated plants belonging to these families can excrete some chemical substances able to attract Frankia and to induce its proliferation
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