Co-inoculation with an arbuscular mycorrhizal fungus and a phosphate-solubilizing fungus promotes the plant growth and phosphate uptake of avocado plantlets in a nursery

An experiment was conducted to evaluate the individual and combined effects of treatment with the phosphate solubilizing fungus Mortierella sp. and the arbuscular mycorrhizal fungus Rhizoglomus fasciculatum on the plant growth and phosphate uptake on plantlets of avocado (Persea americana Mill. cv. 'Hass') grown in a nursery. A completely randomized test design was used. Treatments consisted of individual and combined inoculations with R. fasciculatum and Mortierella sp. at two concentrations (10(6) and 10(8) CFU.mL(-1)), and the results were compared with an uninoculated control. The plant height, shoot dry mass, and shoot phosphate uptake were significantly higher in plants inoculated with both of the fungi than with either fungus individually, or in the uninoculated control plants. The colonization of fine roots with both fungi decreased when they were co-inoculated by comparison with when they were individually inoculated, which suggests that these fungi compete for root space. Despite this competition, the dual inoculation showed that the fungi had additive effects on plant performance. Thus, shoot phosphate levels in plantlets inoculated with mycorrhizae was significantly higher when Mortierella sp. was co-inoculated at both concentrations, compared with the single inoculations and the uninoculated control plants (mycorrhiza free).