Arbuscular mycorrhizal fungi might alleviate aluminium toxicity in banana plants

Some mycorrhizal plants exhibit greater resistance than nonmycorrhizal plan ts to aluminium toxicity. This has not yet been shown for banana despite it s importance as a cash and food crop in tropical regions, although bananas are sensitive to aluminium stress. We studied the effects of the arbuscular mycorrhizal fungus Glomus intraradices in alleviating aluminium toxicity i n the banana cultivar Grande Naine grown in a continuous-nutrient-flow cult ivation system using dilute solution. The micropropagated plants, some of w hich were inoculated with arbuscular mycorrhizal fungus, were grown for 40 d in pots filled with sand, and continuously irrigated with a nutrient solu tion containing up to 180 muM of aluminium. Water and nutrient uptake were measured once a week for 24 h, and root arbuscular mycorrhizal fungal colon ization, biomass production, and mineral content of roots and shoots were m easured at harvest. The root arbuscular mycorrhizal fungal colonization was large, and not significantly influenced by aluminium treatment. The effect s of aluminium on both mycorrhizal and nonmycorrhizal plants were: decrease in biomass production, water and nutrient uptake, and magnesium content of roots and shoots; greater aluminium content in roots than in shoots; and i ncrease in potassium and phosphorus content, particularly in roots. A signi ficant positive effect of arbuscular mycorrhizal fungi on plant growth was observed with aluminium treatment, and was most pronounced at the highest c oncentration. The benefits, compared with nonmycorrhizal plants, included: increase in shoot dry weight, uptake of water and of most nutrients, and in calcium, magnesium and phosphorus content, particularly in roots; decrease in aluminium content in root and shoot; and delay in the appearance of alu minium-induced leaf symptoms. These results indicate that arbuscular mycorr hizal fungi could be effective in alleviating aluminium toxicity to banana plants.