Bioformulations based on Trichoderma and Azotobacter consortia modulate composition and improve biological activity of sweet basil (Ocimum basilicum L.) cv. Genovese essential oil

Basil (Ocimum basilicum L.) is widely cultivated for its economic value. Recently, diverse cultivation management practices have emerged to enhance the productivity and quality of plants and their bioactive compounds, including essential oils (EOs). In this study, bioformulations based on Azotobacter chroococcum 76A (76A), Trichoderma afroharzianum T22 (T22), 6-pentyl-α-pyrone (6PP, a lactone produced by Trichoderma), and a biopolymer (BP), were tested on sweet basil cv. Genovese grown in protected cultivation. The effects of the bioformulations on basil EO content, composition, and biological activities were evaluated. The content of EOs from biotreated plants in 6 out of the 9 bioformulations increased up to 0.68 % w/w in the treatment vs. 0.25 % w/w in the control. The bioformulation applications to the plants modified EOs composition, as was demonstrated by GC-MS analysis, particularly regarding eugenol and linalool percentages. All basil EOs inhibited the growth of different bacterial and fungal strains and reduced biofilm production in plate assays, but EOs from plants treated with T22 alone or in combination with 76A showed better performances, e.g. the EO from T22 + 76A treated plants inhibited up to 92.9 % biofilm production in Escherichia coli, demonstrating potential as alternative to synthetical chemical products for disease control applications in agriculture. The ability of EOs to prevent ROS formation and their wound-healing activity in vitro were also examined, with EOs from T22 + 76A treated plants demonstrating the major antioxidant activity. Our findings support the development of innovative formulations based on microbial consortia that can stimulate the production of aromatic and nutraceutical compounds in basil leaves.