In Vitro and In Vivo Inhibition of Cylindrocladium reteaudii by Essential Oils of Acorus calamus Rhizomes

Abstract

Cylindrocladium reteaudii (Bugnic.) Boesew. is a severe pathogen which can cause leaf blight disease in Eucalyptus seedlings in tropical countries. This study investigated the antifungal activity of essential oils extracted from Acorus calamus L. rhizomes in inhibiting the growth of C. reteaudii, both in in vitro and in vivo experiments. The extraction of essential oils from rhizomes was carried out by hydro-distillation technique and the in vitro antifungal testing was done by using the poisoned food technique. The results indicated that an essential oil concentration of 2,000 ppm can completely inhibit the fungal growth with a 50% inhibitory concentration value of 54.76 ppm. For the in vivo experiment, it was found that an essential oil concentration of 500 ppm and Captan® of 1,000 ppm were not significantly different in inhibiting the growth of C. reteaudii. However, these two treatments significantly inhibited the fungal growth (p<0.05) when compared with the control treatments. Physiological and anatomical characteristics were investigated to check for the antifungal activity after the application of essential oils. Results showed that essential oil spraying had no effect on the leaf transpiration rate and temperature of the Eucalyptus seedlings, but the incident disease ratio was high when an essential oil concentration of more than 1,500 ppm was applied. Therefore, it can be inferred that the essential oils from A. calamus rhizomes at an optimum concentration can be an efficient antifungal compound with a potential to control leaf and shoot blight diseases in Eucalyptus seedlings in a nursery.