Chemical composition and antibacterial activity of the essential oil and extracts of Cistus ladaniferus subsp. ladanifer and Mentha suaveolens against phytopathogenic bacteria and their ecofriendly management of phytopathogenic bacteria

This study aims to determine the phytochemical compounds of Cistus ladaniferus subsp. ladanifer and Mentha suaveolens and the investigations of their antibacterial effects against phytopathogenic bacteria. The chemical composition of Cistus ladaniferus subsp. ladanifer essential oils (CLEO) and Mentha suaveolens essential oils (MSEO) was determined using GC-MS analysis. The determination of phenolic content (TPC) of ethanolic, methanolic, and water plant extracts was realized by the Folin-Ciocalteu method. In vitro antibacterial activity was tested against Pseudomonas savastanoi pv. savastanoi 2636-40 and Clavibacter michiganensis subsp. michiganensis 1616-3 using agar disc diffusion and microdilution assay. Efficacy of the extracts in the treatment of the tomato infected seeds by Clavibacter michiganensis in Petri plate assays. The chemical composition of MSEO revealed the presence of piperitenone oxide (39.11%), and germacrene D (13.6%) as a main compound. However, viridiflorol (28.82%) and Ɣ-gurjunene (14.61%) were the main compounds of CLEO. Among the extracts of Mentha suaveolens, the methanolic extract is the richest in phenol content (112.04 ± 2.98 mg EAG/g of extract), while the aqueous extract is richer on phenol content (76.98 ± 4.6 mg EAG/g of extract) for Cistus ladaniferus. The antibacterial activity showed important inhibition of plant pathogenic bacteria. The Petri plate assays indicated that 4×MIC of methanolic extract of C. ladaniferus showed the highest percentages of tomato germination seeds inoculated by C. michiganensis with rates of 77.77%. These findings suggest that methanolic extract of Cistus ladaniferus may be used as ecofriendly management of plant pathogens bacteria. However, further investigations concerning the identification of phenolic compounds of these plant extracts and the evaluation of antibacterial mechanism against plant pathogens bacteria are required.