INFLUENCE OF INOCULATION WITH ARBUSCULAR MYCORRHIZAL FUNGI ON THE GROWTH AND MYCORRHIZAL INFECTION OF TRANSPLANTED ONION

Effects of inoculation with arbuscular mycorrhizal (AM) fungi on the growth and mycorrhizal infection of onion were observed in five field experiments. Onion seedlings pre-inoculated in multiple trays with peat substratum were transplanted after 6 weeks to the field plots containing steamed, fumigated or non-sterilised soil. Positive growth responses were found after inoculation with most fungal endophytes tested. Inoculated AM fungi were generally more effective than indigenous fungi from non-sterilised soil. The plant growth response to inoculation was higher when indigenous fungi in the soil were eliminated by steam sterilisation or fumigation. In one experiment, inoculation was most effective in non-fertilised and non-irrigated treatments, but the mycorrhizal growth response of the plants inoculated by some fungi was significant even when plants were fertilised and irrigated.