Beneficial soil microorganisms for agroecological transition towards innovative low-input, safe and resilient agroecosystems

Introduction. Weeds pose a major threat to the sustainability of EU farming systems, with weed management largely relying on herbicides use. Herbicides have a high impact on ecosystems’ health, decreasing biodiversity, causing soil moisture depletion and increasing environmental pollution, being also potentially hazardous to human health. Accordingly, the reduction of herbicide use represents a major policy target of EU initiatives aimed at reducing by 50% the use of agrochemicals by 2030. In order to achieve such goals and with the aim of improving the sustainability and resilience of agroecosystems, the Horizon Europe project GOOD (AGrOecOlogy for weeDs) is developing novel Agroecological Weed Management strategies combining the use of cover crops with seed inoculation of beneficial microorganisms, such as arbuscular mycorrhizal fungi (AMF), along with the use of digital tools. Such approaches are being tested in Living Labs (LLs) from seven European countries (the Netherlands, Serbia, Italy, Greece, Portugal, Spain, and Cyprus) and involve both annual and perennial crops, as well as conventional, organic, and mixed farming systems. Aim of the work. The aim of the present study, within the framework of the GOOD project, was to characterize and reproduce the native soil AMF communities of 14 European LLs, to be used as seed inocula to promote the competitive ability of cover crops against weeds. Materials and methods. AMF spores were extracted from the soil of each of the 14 LLs, identified and quantified. The AMF communities were then massively reproduced in pot cultures, given their status of obligate biotrophic symbionts, using three highly mycotrophic host plants (Vicia villosa, Cichorium intybus, and Medicago sativa). Moreover, a protocol was developed and tested on seeds of 11 plant species varying in shape, size and weight, to use seed inoculation as a means of delivering native AMF communities to cover crops. Results and discussion. The highest spore numbers were found in Italian, Greek and Dutch soils (256, 225 and 217 spores/50 g soil, respectively), while the lowest numbers were found in Cyprus and Portugal (31 and 37 spores/50 g soil). AMF richness differed among European LLs, with 17 AMF species in Spanish LLs and 4-5 in Italy and Cyprus. Some species, such as Entrophospora etunicata, Glomus badium, Pacispora sp. and Rhizoglomus spp. were retrieved in 3-5 LLs, while spores belonging to Ambisporaceae, Archaeosporaceae, Acaulosporaceae and Scutellosporacerae were found at very low density in many LLs. Seed inoculation protocol was set up using different quantities of AMF inoculum, a commercial liquid adhesive material and water, to ensure uniform coverage of seeds. The protocol was then scaled up for on-farm application. Future studies will be carried out in order to assess the increase of the mycorrhizal inoculum potential of LLs soils and the changes in the native AMF communities after cover crop inoculation. The use of AMF inoculum and cover crops will promote long-term and large-scale agroecological transition towards innovative low-input, safe and resilient agroecosystems