Inoculation of arbuscular mycorrhizal fungi increases lettuce yield without altering natural soil communities

Agricultural practices may lead to a decline in the presence and abundance of natural arbuscular mycorrhizal fungi (AMF). AMF inoculation can be an environmental friendly alternative or complement to chemical fertilizers in agriculture. Initially, through ribosomal DNA internal transcribed spacer (ITS) metabarcoding, we characterized the composition of fungal communities from three organic orchard soils, as well as from three adjacent non-cultivated soils. Organic orchard management had a negative impact on AMF community, leading to reduced alpha diversity and relative abundance of AMF taxa, compared to non-cultivated soil (e.g. 10 vs. 11 in richness and 2.1 vs. 2.6 in Shannon index). Using trap plants, we multiplied the AMF communities from the abovementioned orchard and non-cultivated soils. Afterward, a microcosm experiment was carried out to study the effect of inoculation with these AMF communities on (i) lettuce (Lactuca sativa L.) yield and nutritional quality (two consecutive crops), and (ii) root fungal communities. During the second crop cycle, AMF inoculants led to higher lettuce yields (by an average of 186%, irrespective of the origin of the inoculum), but resulted in no substantial modification of lettuce nutritional quality. Moreover, AMF inoculants did not exert a significant effect on fungal (including AMF) or AMF communities.

Automated summary

Agricultural practices can negatively impact the presence and diversity of AMF, while organic orchard management leads to a decline in AMF abundance. Inoculation of AMF can increase lettuce yield but does not significantly alter nutritional quality. Additionally, AMF inoculation does not have a substantial effect on root fungal communities.