Four vesicular arbuscular mycorrhizal (VAM) fungi (Glomus spp.) isolates namely VAM-O, VAM-B, VAM-S and VAM-M were isolated from onion, broad bean, swiss cheese and maize roots, respectively, used to produce in vitro inocula which were evaluated under field conditions. The VAM isolates were grown in vitro on barely modified (BM) cultures to produce their applicable inocula. The in vitro inocula were used at low (2.5/g ridge), medium (5.0/g ridge) and high levels (10.0/g ridge) equivalent to 10, 15 and 20 kg/feddan, respectively. Two field experiments were carried out during 2002 and 2003 growing seasons to evaluate the effect of VAM inoculation treatments compared to P-fertilizer and VAM inoculation + N-fertilization compared to N-fertilizer alone on the seed germination, percentage of smutted and stunted plants, fresh and dry weight/plant, ear weight, grain yield/plant and weight of 100-kernels. Response of maize to VAM inoculation was greatly varied depending on the VAM isolate, inoculum level and growing season. The aforementioned maize growth parameters were significantly enhanced by VAM inoculation than P-fertilization, whereas most VAM treatments + N-fertilization showed similar response when compared with the N-fertilizer alone.
Keywords: Vesicular arbuscular mycorrhizae, VAM, inoculum, in vitro, P-fertilization, N-fertilization, common smut, stunt, maize.