Chemical profiling and enhanced antifungal activity of the origanum hybrid (Origanum majorana × O. syriacum var. bevanii) essential oil against Sclerotinia sclerotiorum

This study investigated the chemical composition and antifungal activity of essential oils (EOs) obtained from Origanum majorana (Oma), O. syriacum var. bevanii (Osyr), their interspecific hybrid (M4), and a 1:1 mixture of the parental EOs (EO mixture). Specifically, the bio-efficacy of these EOs was evaluated against Sclerotinia sclerotiorum, the causative agent of white mould disease. GC-MS analysis revealed distinct chemical profiles: Oma EO was dominated by terpinen-4-ol (36.0%) and γ-terpinene (18.1%), while Osyr EO contained high levels of thymol (33.3%) and carvacrol (30.0%). The M4 hybrid EO exhibited a significant shift, with carvacrol (41.5%) as the major component, alongside thymol (16.2%) and reduced terpinen-4-ol (12.3%). The 1:1 EO mixture showed intermediate levels of thymol (24.6%), carvacrol (21.7%) and terpinen-4-ol (16.4%). Antifungal tests showed that the M4 Hybrid EO was the most effective, achieving 100% inhibition at 1.0 µL/petri, followed by Osyr EO (2.0 µL/petri) and the EO mixture (2.0 µL/petri), while Oma EO required a much higher dose (15.0 µL/petri). The increased activity of M4 and Osyr EO was attributed to their high content of phenols (carvacrol and thymol), which are known to destroy the cell membranes of fungi. The study concluded that hybridisation and mixing of EO compositions can be optimised for superior antifungal activity and offer sustainable alternatives to synthetic fungicides. These results emphasise the potential of Origanum hybrids and EO mixture for environmentally friendly crop protection strategies.