The effect of an in vitro monoxenically produced arbuscular mycorrhizal fungus (AMF), i.e. Glomus intraradices on the growth and phosphorus content of micropropagated banana (Musa spp. c.v. 'Grand Naine') plantlets was investigated in a pasteurized and non-pasteurized Vertisol. The experiment was conducted as a 2 x 2 randomly factorial design with the Vertisol pasteurized or non-pasteurized and the plants inoculated or non-inoculated with the AMF. The plants colonized by AMF had larger shoot and root dry weight and P content than the non-mycorrhizal plants. The largest growth increment was observed in the plants inoculated during the weaning phase with the monoxenic AMF inoculum and subsequently grown in the pasteurized soil. The native AMF population also induced a marked increase in plant growth supporting further the efficiency of this natural population, whereas both inoculum sources in combination did not yield the largest growth increment. The latter suggests a competitive phenomenon between the introduced AMF and the other soil micro-organisms including the native AMF population. Our results demonstrate, for the first time, the potential benefits of a monoxenically produced AMF in micropropagated banana plants.