Boosting coffee seedling performance through arbuscular mycorrhizal association

We evaluated the effects of arbuscular mycorrhizal fungi (AMF) inoculation on growth, root system architecture, and photosynthetic performance of Coffea arabica seedlings. In a greenhouse experiment using unsterilized soil, seedlings were grown either with (+ M) or without (-M) the addition of AMF inoculum. +M plants exhibited higher net CO₂ assimilation rates and maximum carboxylation capacity of RuBisCO despite reduced stomatal conductance (and transpiration rates), resulting in improved water-use efficiency. These physiological adjustments were associated with greater photochemical utilization of incident light. In addition, +M plants showed increased foliar phosphorus concentration and shifts in leaf metabolic profiles, characterized by higher starch and total free amino acids, reduced hexose sugars, and unchanged sucrose and protein concentrations. Compared with -M plants, +M seedlings displayed pronounced modifications in root system architecture, including greater total root length, surface area, and volume, with a higher proportion of fine roots, while biomass partitioning remained unchanged. Collectively, these morphological and physiological responses resulted in superior vegetative growth in + M plants. AMF inoculation thus represents a promising approach to produce more vigorous and stress-resilient coffee seedlings, potentially facilitating field establishment and reducing production costs.