Relation between arbuscular mycorrhizal fungi, root-lesion nematodes and soil characteristics in maize agroecosystems

Native communities of arbuscular mycorrhizal fungi (AMF) and root inhabiting nematodes were examined in nine maize plots of conventional smallholders in Mexico differing in geographic location, soil properties and agricultural practices. Total species richness of AMF revealed 34 spore morphotypes, 27 of which were identified to species level and 7 to genus level. Only four AMF species were recovered from all nine maize plots: Paraglomus occultum, Funneliformis mosseae, Gigaspora albida and Acaulospora splendida. In the field, fine roots from all plots were colonized by AMF during the full crop cycle with highest colonization at flowering. AMF colonization responded to soil characteristics, mainly P, Ca and pH. Lowest AMF root colonization was found in maize plots with higher soil P levels. Eggs and adults of the endoparasitic root-lesion nematode (Pratylenchus spp.) were frequently observed with highest abundance at the vegetative plant growth phase. In addition, correlation analysis revealed complex interactions between nematode abundance and AMF root colonization depending on both maize growth phase and maize plots. The AMF from the field rhizosphere soil were propagated in pots under greenhouse conditions to produce AMF spores in better conditions and to corroborate their identity. When maize plants were grown in pots with a sterile phosphate-limiting substrate and supplemented with non-sterile soil from the plot sites harbouring native AMF communities, maize growth was strongly promoted allowing to reach flowering. This information will be useful to establish agricultural practices of maize cultivation that promote the use of native AMF.