Volatile organic compounds activities of Trichoderma species isolated from olive grove soil against the wilt pathogen, Verticillium dahliae

Abstract

Production of volatile organic compounds (VOCs) is one of the modes of actions of Trichoderma spp. They inhibit pathogenic fungi/bacteria, promote plant growth, and also affect interactions of plants with pathogens. However, the study of VOCs emitted by Trichoderma species associated with olive roots and its benefits are still limited. In the present study, two strains of Trichoderma collected from olive grove soil were evaluated for their antagonistic activity against five strains of Verticillium dahliae named (Vd1 to Vd5) by indirect confrontation assay. In addition, identification and quantification of volatile compounds produced by each strain were assessed through gas chromatography-mass spectrometry (GC–MS). The extraction of metabolites was performed from filtrates using liquid–liquid extraction. Extracts obtained were taken for analysis through GC–MS. Results of indirect confrontation assay showed a high inhibitory activity against V.dahliae. Trichoderma asperellum (T4) and Trichoderma harzianum (T12) exhibited an average inhibition rate of 64.49% and 61.59% respectively. Besides, 98 volatile compounds were detected through GC–MS analysis, including important volatile compounds with antifungal activities, such as D-limonene, octadecanoic acid methyl ester, hexadecanoic acid, toluene, phenylethyl alcohol, benzene derivatives, several phenolic isomers, citral, eicosane and 13-docosenamide. Other volatile compounds revealed antibacterial activity, providing growth promotion, or antioxidant activity, such as oleic acid. Importantly, 7-epi-nemorosone was detected for the first time as new molecule produced by Trichoderma harzianum (T12). This molecule provides anticancer and antioxidant activity. Overall, these strains with various activities are considered as excellent source for discovery of bioactive molecules with eventual application in different biological fields. However, they could be beneficial mainly for suppressing plant pathogens and stimulation of plant growth.