Comparative Evaluation of Two Commercial Propolis Extracts as Plant Defense Activator and Antimicrobial Agent Against Pseudomonas syringae pv. tomato (Pst) strain DC3000

Abstract

Propolis is a natural bee product that protects the beehives from internal and external factors. It is a natural-complex compound with a wide potential use as an antimicrobial, anti-fungal, and anti-inflammatory effect. The role of propolis as a plant protection agent and an alternative to pesticides is an unexplored area. Here, two different commercially available propolis extracts were evaluated for antibacterial effects on Pseudomonas syringae pv. tomato (Pst) strain DC3000. Also, the activities of defense response genes WRKY70 and CaBP22 in Arabidopsis thaliana under propolis application were compared. According to the results, each propolis extract and dose had a different effect on gene expressions as well as antibacterial activity. One of the commercial brands had a significant effect at all doses while another brand’s propolis extract had its activity at only 1% concentration. Propolis reduced bacterial growth up to 93% with a 2% concentration. For the first time, propolis is also evaluated for its capacity as a plant defense activator agent and it induced WRKY70 and CaBP22 gene expression. The differences in gene expression and bacterial growth inhibition levels suggest the importance of the origins of propolis, such as plant species and regions it collected. While preliminary in nature, these results suggest a significant potential of propolis in plant protection in commercial and organic agriculture.