Effect of Arbuscular Mycorrhizal Inoculation on the Growth, Nutrient Uptake and Root Infectivity of Tropical Fruit Seedlings

The effect of arbuscular mycorrhiza (AM) fungi on growth, nutrient uptake and root infectivity was determined in passion fruit (Passiflora edulis var. edulis), rough lemon (Citrus limon) and papaya (Carica papaya var. solo) seedlings raised under four phosphorus regimes (0, 0.44, 0.88 and 1.68 mg/ml) in sand culture and also in sand/nitrosol sterile and unsterile conditions. Inoculation with AM fungi increased the plant height, leaf number and stem girth in relation to un-inoculated seedlings grown under equivalent P concentrations. An increase in plant height, leaf number and stem girth also occurred in both inoculated sterile and un-sterile sand/nitrosol media in relation to un-inoculated sterile and unsterile media. AM also increased the leaf area and the root, leaf and stem fresh and dry weights and also caused an increase in the uptake of phosphorus in the leaf tissues. It also favored mycorrhizal infectivity of roots and increased the root absorptive surface area. This study indicates that AM fungi improves tropical fruit seedling performance by increasing the capacity of roots to absorb and utilize plant nutrients and also by increasing the effective root surface area from which available form of nutrients are absorbed.