Intracellular Burkholderia strain has no negative effect on the symbiotic efficiency of the arbuscular mycorrhizal fungus Gigaspora margarita

This study investigates the effects of bacteria occurring in the cytoplasm of some arbuscular mycorrhizal fungi (AMF) on their symbiotic efficiency. Gigaspora margarita, Gigaspora rosea and Glomus versiforme, containing or without intracellular bacteria, were compared for their efficiency in stimulating growth of Lactuca sativa L. Biomass production and nutrient contents were evaluated in plants grown on two substrates. The efficiency of G. margarita harbouring a homogenous population of Burkholderia was greater than that of the other two AMF, mainly G. rosea, which does not contain intracellular bacteria. When plants were grown in poor soil, inoculation with G. margarita resulted in the best growth rates as well as the highest N, P and K values. The significantly higher N content is of particular importance, since the genome of Burkholderia possesses nif genes.