Abstract

Purpose This study was conducted in order to verify the ability of the legume Sophora cassioides to grow in a recent volcanic deposition and to assess for the first time the presence and diversity of symbionts such as arbuscular mycorrhizal fungi (AMF) and bacteria present in nodules. Material and Methods The legume was grown under greenhouse conditions for a year, in substrate collected from Choshuenco volcano (CH), and compared with cultivation in a well-developed soil (SR). Bacterial isolates were obtained from nodules in both CH and SR and were analyzed by PCR to evaluate the presence of genes homologous to nodC and nifH. As a first approach, bacterial identity and diversity were assessed by sequence analysis of the 16S rRNA gene. The presence of AMF in the roots was evaluated by staining and sequence analysis of the small subunit ribosomal ribonucleic acid (SSU rRNA) gene fragment. Results Sophora cassioides grew less in CH substrate, and nodules were more frequent but heterogeneous in size and shape compared to nodules from SR. AMF colonization was about 48% in both substrates. PCR indicate that 74% of isolates from CH and 46% from SR carried genes homologous to nodC and nifH and are probably able to form nodules and to fix nitrogen. 16S rRNA gene fragment analysis from twelve PCR-positive isolates showed that all of them belong to the Rhizobium genus, but to different species. The analysis of SSU rRNA gene fragment, amplified from roots of plants grown in CH and SR, identified the presence of five AMF species or genus. Conclusions Sophora cassioides showed a tripartite and promiscuous symbiosis. Up to date, this is the only Sophora species described able to grow in a recent volcanic deposition. The potential of this legume to restore volcanic affected soils is discussed as well as the role of the described symbionts in plant adaptation to grow in volcanic depositions.