Antifungal effects of three plant essential oils against Rhizopus stolonifer, the cause of soft rot on strawberry fruit

Usually, many chemical fungicides are used to control fungal infections. However, some of these fungicides are harmful for human health. The goal of this study was to examine the essential oils of certain medicinal plants to control the fungi and replace the chemical fungicides. One of the most important and widespread fungi that infects strawberries during the post-harvest period is Rhizopus stolonifer. The effects of essential oils of three plant species: Satureja hortensis, Zataria multiflora and Carum copticom on the mycelial growth of Rhizopus stolonifer were tested both in vitro and in vivo on a medium of potato dextrose agar in seven concentrations (100, 200, 300, 500, 1000, 2000 and 10000 ppm). The in vivo experiment contained six groups: three essential oils, one fungicide and two controls. Each treatment consisted of three replicates and each replicate included five strawberries each weighing about 70 grams. Each fruit was disinfected, placed in a suspension of 106 spores per milliliter of Rhizopus stolonifer; and then placed in a suspension of either the essential oil or fungicide (Iprodione + Carbendazim 52.5% WP). The fruits were kept at room temperature (24 ±1°C). Results showed that the critical inhibitory concentration of Rhizopus stolonifer was 300 ppm for Satureja hortensis and Carum copticom and 500 ppm for Zataria multiflora. On the other hand, in vivo experiments showed that the greatest amount of remaining fungus was in the following order: control groups, Carum copticom, Zataria multiflora and Satureja hortensis.