Genetic, phenotypic and functional variation within a Glomus geosporum isolate cultivated with or without the stress of a highly alkaline anthropogenic sediment

Genetic, phenotypic and functional variation in a Glomus geosporum isolate obtained from a highly alkaline anthropogenic sediment was investigated. Two cultivation lineages of G. geosporum (BEG199 and BEG211) were created by sub-culturing with or without the stress of the sediment. Genetic variation was assessed on spores from both cultivation lineages in the large sub-unit rRNA gene D2 region using PCR-single strand conformational polymorphism (PCR-SSCP) and sequencing. Phenotypical and functional variation of the cultivation lineages were assessed after inoculation onto Conyza bilbaoana. The sequence diversity obtained in G. geosporum BEG211 was significantly different from that obtained in G. geosporum BEG199. Glomus geosporum BEG199 was more effective than G. geosporum BEG211 in promoting the growth of C. bilbaoana in inert substrate and in increasing its leaf phosphorus concentration when the plant was grown in sediment. After inoculation onto C. bilbaoana, G. geosporum BEG199 colonised the roots to a greater extent, produced a significantly larger number of spores and presented a greater length of extraradical mycelium than G. geosporum BEG211. The results indicate that environmental conditions under which arbuscular mycorrhizal fungi (AMF) are cultivated can influence their effects in host plants. Also, AMF might quickly lose gained-tolerance to environmental stresses when maintained without the selective pressure of those stresses. This study has implications for the production of commercial inoculum of AMF and for the maintenance of AMF cultures. The results indicate that inoculum of AMF should be produced and AMF cultures should be maintained in substrates or media containing the original edaphic stresses.