Effects of Crop Management System on Arbuscular Mycorrhizal Fungi (AMF) Diversity, and Its Influence on Soybean Tolerance to Water Stress.

The development of an agriculture based on the intensive use of inputs allowed a considerable increase in the productivity of crops. However misuse of these practices can lead to soil degradation processes that are associated with loss of soil organic matter which affect the density and diversity of soil microorganisms. Recent studies indicates that one of the microorganisms most affected by agronomic management are the communities of mycorrhizal fungi, which have been classified as relevant given that they not only increase the growth of plants, absorption of water and nutrients, stabilization of soil aggregates and the soil carbon content, but they also have a great potential to protect plants under water deficit conditions.

However, it is unknown if inocula of two different farm management systems can affect the ability that has these fungi to overcome or compensate the negative effects of the water shortage in the plants. For that reason this study aims to compare the effect of two inocula of AMF from two production, in the physiological response of soybean plants to water deficit. This experiment was conducted under greenhouse conditions, in which soybean plants were inoculated with different two AMF (Arbuscular mycorrhizal fungi) inoculum; one from a conventional system (CVF) and the other one from an organic system (OGF), then plants were subjected to a moderate water deficit.The results obtained indicate that the organic system inoculum generated a more abundant and diverse AMF community, providing to soybean plants a better response in water deficit conditions, which is reflected in an increase in production, through increased stomatal conductance (Control= 0,420; CVF=0,543 and OGF=0,516 mol m^-2 s^-1), biomass gain (Control= 9,64g; CVF=12,06g and OGF=17,43g) and increased the dry weight of pods (Control= 5,95; CVF=9,05g y OGF=12,53g) under water deficit.

In conclusion the presence of AMF inoculum from organically managed soils is beneficial for soybeans to tolerate water deficit, allowing a better status of plants and therefore increasing production under these conditions.