Basil (Ocimum basilicum L.) is a high-value medicinal herb cultivated for economical applications, especially pharmaceuti-cal purposes. There is less information on the effects of arbuscular mycorrhizal (AM) fungi, drought stress, and phosphorus (P) supply on important phenolic compounds like caffeic (CA) and rosmarinic (RA) acids. Therefore, an experiment was performed to examine whether treatments: AM (inoculated with Glomus hoi and non-inoculated (NM) plants; drought stress (60% field capacity (FC)) and well-irrigated (90% FC) and phosphorus supply (0.1, 0.2 and 0.3g/kg of soil) could influence plant growth and contents of total phenols (TPC), RA, CA and phenylalanine ammonia-lyase (PAL) activity. The experiment was conducted as a factorial oriented by completely random design with three repetitions. Shoots of 8-week-old plants that were subjected to all mentioned treatments were harvested and analyzed. High-performance liquid chromatography (HPLC) was used to quantify RA and CA contents. Results indicated that both P supply and AM inoculation enhanced plant growth, tissue P content, RA and CA production and PAL activity. There was an increase of 1.84, 1.59, and 2.22 times for TPC, RA and CA contents respectively in AM plants compared to NM plants in P2 levels and in drought stress. There was a positive relationship between the phenol content and PAL activity for all the treatments. Consequently, mycorrhizal inoculation and application of an appropriate level of P could serve as an adaptive strategy to enhance productivity and plant synthesis of phenolic compounds under restricted irrigation with health-promoting activities.

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