RESPONSE OF CRIOLLO MAIZE TO SINGLE AND MIXED-SPECIES INOCULA OF ARBUSCULAR MYCORRHIZAL FUNGI

We tested the effect of two single species inocula and a mixed inoculu m of the native population of arbuscular mycorrhizal (AM) fungi on the growth response of ''criollo'' maize (Zea mays L.). To determine the inocula that produced the highest response on maize growth, we conduct ed a greenhouse experiment at 3 levels of P fertilization (0, 40 and 8 0 kg ha(-1)). Inoculation with Glomus mosseae (Nicolson and Gerdemann) Gerd. and Trappe (LMSS) produced the greatest shoot growth rates at t he two lowest P fertilization levels. Inoculation with Acaulospora bir eticulata Rothwell and Trappe (ABRT) and the native population (NP) re sulted in similar shoot growth rates at all P levels. These rates were higher than the non-mycorrhizal control rate at the lowest P level bu t lower than the control at the highest P level. Also, ABRT and NP had significantly lower shoot growth rates than the inoculation treatment with G. mosseae at all P levels. The non-mycorrhizal control had the lowest growth rate at the lowest P level but its growth rate increased linearly with increased P fertilization. Inoculation with G. mosseae and A. biretuculata produced similar colonization rates which were low er than the native population colonization rate. There was no correlat ion between colonization and shoot growth rates.