Inhibitory effect of essential oils from Pulicaria mauritanica and Micromeria debilis on growth of Alternaria spp., the causal agent of tomato early blight

Abstract

The aim of the present study was the evaluation of antifungal activity of essential oil (EO) extracted from two medicinal and aromatic plants (Pulicaria mauritanica and Micromeria debilis) as biological treatment for Alternaria spp., a pathogenic mould that causes early blight on tomato plants. EO was extracted by hydrodistillation and antifungal activity was analyzed in vitro using direct contact on agar against ten isolates of Alternaria spp. Extraction yield was 0.30 and 0.045% for P. mauritanica and M. debilis, respectively. Both EOs had inhibitory effect against mycelial growth of all studied isolates. However, the antifungal effect of EO isolated from P. mauritanica was stronger than for that from M. debilis, with 100% inhibition against Alternaria tenuissema (isolates A18 and A57), Alternaria alternata (isolate AT4), Alternaria solani (A37) and Alternaria tomatophila (AT01), when used at 1.1 µL mL–1 concentration. EO from M. debilis had 100% inhibition against isolates A42 and A57 of A. solani and A. tenuissema when used at 1.1 µL mL–1 concentration. The antifungal activity of the EOs might due to the synergic effects of their chemical compounds, mainly monoterpenes and sesquiterpenes.