Investigation of antimicrobial effect of aqueous extract of yarrow and pomegranate peel on some pathogenic bacteria of agricultural crops

Regarding to the adverse side effects of chemical pesticides to the environment and human health, use of plant extracts has considerable significance for synthesis of bio-antimicrobial compounds. In the present study, the antibacterial effect of aqueous extract of yarrow (Achillea millefolium) and pomegranate peel was investigated on Bacillus cereus and some important pathogenic bacteria of agricultural crops, including Agrobacterium tumefaciens, Xanthomonas citri subsp. citri and Pseudomonas tolaasii. The extraction was performed by maceration method. Antibacterial effect of extracts was evaluated using agar well diffusion method at four concentrations. Distilled water and Gentamycin disc were used as negative and positive control groups, respectively. The experiment was set up as factorial in completely randomized design (CRD) with four replications and mean comparison was performed by LSD at the probability level of 5%. Mean comparison of the growth inhibition zone diameter in different treatments reveled that both extracts had considerable inhibitory activity against B. cereus and A. tumefaciens. On P. tolaasii, the extract of yarrow showed antibacterial activity and its inhibitory activity was improved with an increase in its concentration. None of the extracts at tested concentrations showed antibacterial activity against X. citri subsp. citri. According to the results, the aqueous extracts of yarrow and pomegranate peel have the potential to be used in control of A. tumefaciens and B. cereus. Consequently, they are good candidates for further assays in order to synthesis safe antibacterial compounds or natural food preservative.