Antifungal activity of Zataria multiflora Boiss. essential oils and changes in volatile compound composition under abiotic stress conditions

There is an increasing need for natural compounds for pest control and food preservation in agriculture, food and dairy industries. To satisfy this need, essential oils (EOs) from aromatic plants can serve as flavors, food preservatives and ecofriendly pesticides. This study investigated the potential of different EOs from field-collected leaves of fourteen Zataria multiflora Boiss. populations representing three different chemotypes (carvacrol, thymol and linalool) to inhibit a broad spectrum of fungal pathogens important in food industry and agriculture and the relationship between total leaf elements concentration and EOs compounds. Furthermore, a greenhouse experiment was performed to elucidate the effects of heat stress (33 ◦C vs. 20 ◦C), drought stress (50 % reduced irrigation), and ultraviolet light intensity (3, 6 and 9 W m-2 UV-A radiation) on the relative content of specific volatile compounds. The results indicated that low concentrations of carvacrol and thymol, but not of linalool chemotype EOs inhibit significantly the growth of pre- and postharvest pathogens Colletotrichum lindemuthianum, Fusarium sambucinum, Fusarium culmorum, Alternaria dauci and Botrytis cinerea (thymol/carvacrol EOs: 0.8-1 μL, linalool EOs: 4 μL). The analyses revealed further significant correlations between the concentrations of mineral elements in Z. multiflora leaves and relative amounts of EO compounds and antifungal activity. Abiotic stresses, particularly heat and the interaction of drought and heat, induced changes in plants of the linalool chemotype resulting in higher relative amounts of carvacrol (22.7 % and 32.9 % vs. 1.5 %), while drought stress alone did not influence the relative amount of the main volatile compounds of Z. multiflora (carvacrol 1.7 %). Furthermore, the relative amount of linalool was slightly reduced in the linalool chemotype, when plants were subjected to high intensities of UV-A radiation (33.9 % vs. 44.6 %), whilst the relative amount of carvacrol was slightly increased (20.1 % vs. 9%). Moreover, the main volatile compounds of plants from the carvacrol chemotype did not change in response to abiotic stresses. Understanding the effect of environmental conditions on aromatic plant populations and chemotype development helps agriculture and food industry fully exploiting the potential of aromatic plants as a source of natural sustainable fungicides or insecticides.