Effects of Three Essential Oils on the Growth of the Fungus Alternaria solani

The early blight of tomato disease, caused by the fungus Alternaria solani, affects the tomato plant,Lycopersicon esculentum, by causing brown leaf spots and concentric black circles on the tomato fruit.In this experiment, it was tested to see if various essential oils have any inhibitory effect on the growthof the Alternaria solani fungus and are able to replace the fungicides, such as azoxystrobin andpyraclostrobin, that are being used or have been used worldwide against the early blight of tomatodisease. Three essential oils fromCarum copticum (ajowan), Zataria multiflora (Shirazi thyme), andSatureja hortensis (savory)- were tested in vitro in a 200 and 400 ppm dosage to examine their effectson the growth of A. solani. The 200 ppm dosage of Carum copticuminhibited the growth of A.solaniby 99.5%, while the 400 ppm dosage allowed absolutely no growth of the fungus over the periodof twelve days. The essential oils of Zataria multiflora and Satureja hortensis were not very effectiveon inhibiting the growth of the pathogen. The 400 ppm of Satureja hortensis even fostered the growthof the fungus. Consequently, Carum copticum can potentially replace the substances that arecommercially used to treat the early blight of tomato disease.