The biosynthesis of health-promoting compounds is modulated by symbiosis with an arbuscular mycorrhizal fungus grown in a high-phosphorus substrate

Phosphorus is a regulatory nutrient in mycorrhizal symbiosis. Notwithstanding, little is known about the efficiency of fungi cultivated in a substrate with high P fertility on the biosynthesis of health-promoting compounds. The study aimed to verify the effect of Acaulospora longula , cultivated in a high-phosphate substrate on the optimization of metabolite production and sun protection factor (SPF) of Zea mays . For this purpose, A. longula was cultivated at two P levels: low P [3 μM KH 2 PO 4 ] and high P [15 μM KH 2 PO 4 ] and inoculated in Z. mays grown in a substrate with two levels of phosphate fertility (22 mg P dm -3 and 39 mg P dm -3 ). The leaves were harvested to evaluate the production of soluble carbohydrates, phenols, tannins, flavonoids, proanthocyanidins, flavonols, aboveground dry matter, and SPF. Contrary to expectations, A. longula grown at high P was more effective at enhancing the production of bioactive compounds in maize grown in the substrate without additional P. On the other hand, a synergistic effect was observed with the isolate grown at low P conditions and a dose of 39 mg P dm -3 , which resulted in improved synthesis of phenols, tannins, flavonoids, and flavonols. The same fungal isolate also enhanced SPF and proanthocyanidin accumulation, regardless of substrate P levels. It is concluded that A. longula is an alternative for increasing the biosynthesis of bioactive compounds relevant to the herbal medicine and phytocosmetics industries. Thus, producers can opt for A. longula cultivated in high P to reduce phosphate fertilizer expenses and to obtain a phytomass of quality due to a higher concentration of health-promoting compounds or A. longula cultivated in low P combined with a fertilizer investment to obtain phytomass with improved bioactive content. • Acaulospora longula produced in a low P substrate keeps its infectivity; • Inoculum production in a P-enriched substrate reduces A. longula infectivity; • Inoculum produced in high P increases metabolite production in maize grown in low P; • Inoculum produced in high P reduces phenolic production in maize cultivated in high P.