Boosting species evenness, productivity and weed control in a mixed meadow by promoting arbuscular mycorrhizas.

Lowland meadows represent aboveground and belowground biodiversity reservoirs in intensive agricultural areas, improving water retention and filtration, ensuring forage production, contrasting erosion and contributing to soil fertility and carbon sequestration. Besides such major ecosystem services, the presence of functionally different plant species improves forage quality, nutritional value and productivity, also limiting the establishment of weeds and alien species. Here, we tested the effectiveness of a commercial seed mixture in restoring a lowland mixed meadow in the presence or absence of inoculation with arbuscular mycorrhizal (AM) fungi and biostimulation of symbiosis development with the addition of short chain chito-oligosaccharides (CO). Plant community composition, phenology and productivity were regularly monitored alongside AM colonization in control, inoculated and CO-treated inoculated plots. Our analyses revealed that the CO treatment accelerated symbiosis development significantly increasing root colonization by AM fungi. Moreover, the combination of AM fungal inoculation and CO treatment improved plant species evenness and productivity with more balanced composition in forage species. Altogether, our study presented a successful and scalable strategy for the reintroduction of mixed meadows as valuable sources of forage biomass; demonstrated the positive impact of CO treatment on AM development in an agronomic context, extending previous observations developed under controlled laboratory conditions and leading the way to the application in sustainable agricultural practices.

Local endoreduplication as a feature of intracellular fungal accommodation in arbuscular mycorrhizas.

The intracellular accommodation of arbuscular mycorrhizal (AM) fungi is a paradigmatic feature of this plant symbiosis that depends on the activation of a dedicated signaling pathway and the extensive reprogramming of host cells, including striking changes in nuclear size and transcriptional activity. By combining targeted sampling of early root colonization sites, detailed confocal imaging, flow cytometry and gene expression analyses, we demonstrate that local, recursive events of endoreduplication are triggered in the Medicago truncatula root cortex during AM colonization. AM colonization induces an increase in ploidy levels and the activation of endocycle specific markers. This response anticipates the progression of fungal colonization and is limited to arbusculated and neighboring cells in the cortical tissue. Furthermore, endoreduplication is not induced in M. truncatula mutants for symbiotic signaling pathway genes. On this basis, we propose endoreduplication as part of the host cell prepenetration responses that anticipate AM fungal accommodation in the root cortex.