Improved growth and antioxidant responses via arbuscular mycorrhizal fungi-mediated changes in phenolic compounds in two tomato landraces under salt stress.

Arbuscular mycorrhizal fungi (AMF) can improve plant performance under salinity, but their contribution to phenolic-based antioxidant responses in traditional tomato landraces remains unclear. We evaluated the effects of Diversispora celata and Funneliformis mosseae on growth, nutrition, gas exchange, oxidative status, and phenolic metabolism in Chilean tomato landraces Limachino and Maulino (Solanum lycopersicum L.) exposed to 0 or 150 mM NaCl. A 3 × 2 × 2 design included three inoculation treatments, two salinity levels, two landraces, and four replicates per combination. Biomass, shoot N and P contents, gas exchange, pigments, proline, lipid peroxidation, antioxidant capacity, and individual phenolics were quantified. Salinity reduced biomass, shoot N and P contents, and net photosynthesis, while non-mycorrhizal plants showed the highest lipid peroxidation. Responses depended on landrace and fungal identity. Under salinity, D. celata-inoculated Limachino plants showed higher biomass, shoot N content, and net photosynthesis than non-mycorrhizal plants, together with greater proline accumulation, higher concentrations of several hydroxycinnamic acids, anthocyanins, quercetin derivatives, total phenolics, and antioxidant capacity, and lower lipid peroxidation. In Maulino, both isolates improved gas exchange; F. mosseae was more closely associated with photosynthetic pigments and TEAC/DPPH capacity, and D. celata with phenolic derivatives and CUPRAC capacity. Overall, AMF responses depended on the host-fungus combination, with phenolic-associated non-enzymatic antioxidant responses emerging as a prominent feature of the Limachino-D. celata association.