Carotenoid Biofortification in Field-Grown Tomato Fruits by Early Inoculation with Arbuscular Mycorrhizal Fungi

Carotenoids are bioactive compounds with relevant health-promoting properties. Thus, a carotenoid-rich diet is essential for improving human health. Beneficial soil microorganisms are used in agriculture as biostimulants to promote plant growth and development and increase their tolerance/resistance to stress. However, their effects on fruit quality have been less studied. In the present study, we assess the impact of early inoculation of tomato seedlings with the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis on carotenoid content in fruits under real agronomic production settings. We show that early inoculation of seedlings with AM fungi provides long-lasting benefits that impact fruit quality, increasing the content of the carotenoids lycopene and β-carotene. We also show that this increase is related to transcriptional upregulation of key genes of their biosynthesis pathway. Our results show that AM fungi, commonly used as biostimulants in agriculture, can also be used as a sustainable strategy for carotenoid biofortification in tomato production systems, contributing to the production of healthy "functional products".