The effect of the co-inoculation of arbuscular mycorrhizal fungi (AMF) and Azospirillum on micro-propagated banana seedlings development during their adaptation phase was determined. At the time of transplanting, banana seedlings were inoculated with an indigenous mycorrhizal inoculum containing 10 spores/g at four doses: 0, 50, 100 and 200 g. Seventy days after fungal inoculation, 20 ml of Azospirillum in four concentrations (0, 106, 107 and 108 CFU/ml) were applied. Finally, after 98 days from the start of the experiment a second dose (40 ml) of Azospirillum in the concentrations mentioned above was inoculated. Plants were harvested 5 months after transplanting and the growth and nutritional parameters were evaluated. The analysis of the data showed that banana plants co-inoculated with 200 g of AMF and 1.5E8 CFU/ml of Azospirillum presented greater development, an increase of 7 times in height, 4 times in perimeter, 16 times in leaf area, 12 times in aerial biomass, and 8 times in root biomass en relación a las plantas control. The results achieved were due to synergism between fungus-bacteria when inoculated at higher doses, with lower doses stimulating growth is minimal. The co-inoculation in high doses demonstrates adequate support and cooperative effect between HMA and Azospirillum crops. In addition, co-inoculation promotes optimal nutritional status because microorganisms allowed plants achieve greater absorption of phosphorus and nitrogen relative to those treated with single inoculation and the control.sphorus and nitrogen relative to those treated with single inoculation and the control.
Key words: Kew words: Arbuscular mycorrhizal fungi (AMF), Azospirillum, Growth, Nutrition, Banana plantlets.