The effect of some volatile organic compounds on the biological control of fungal and pseudofungal pathogens isolated from Rosmarinus officinalis

Fungal diseases cause a massive reduction in the production of rosemary plants every year. Volatile organic compounds (VOCs) can provide valuable fungal bio-pesticides for practical usage. However, the effect of VOCs on the pathogenic fungi of rosemary is poorly studied. This research characterized some fungal pathogens (Rhizoctonia solani, Fusarium oxysporum, Phytophthora infestans, and Phytophthora citrophthora) isolated from rosemary plants. We studied the inhibitory effect of VOCs, including isovaleric acid, 1-octene-3-ol and 3-octanone on growth and disease incidence of isolated fungi under in vitro and greenhouse conditions. The action of individual VOCs on the growth indices of infected plants was also investigated. 1-octen-3-ol showed the most efficacy percentage and inhibitory effect on mycelial growth at five mg/l concentration. Isovaleric acid decreased fungal growth and disease incidence at 10 mg/l as high as 94.74% and 87.23%, respectively. However, 3-octanone had no significant efficacy percentage and inhibitory effect on mycelial growth. 1-octen-3-ol enhanced the growth of fungal-infected plants to the highest amount, but 3-octanone did not increase the growth of infected plants. The obtained data revealed that the different effects of various VOCs on fungal pathogens are related to different chemical structures and action mechanisms of volatile compounds and the species of fungi involved.