Investigation of the antibacterial effects of different plant extracts against pea bacterial leaf blight disease caused by Pseudomonas syringae pv. pisi

Pseudomonas syringae pv. pisi causing pea bacterial leaf blight disease in pea production areas all over the world is a seed-borne pathogen. The initial symptoms of the disease are observed as water-soaked stains on the cotyledon leaves and turn into necrotic stains at a further stage. In this study, the antibacterial properties of plant extracts has tested against Pseudomonas syringae pv. pisi. For this purpose, 34 different medicinal and aromatic plant extracts were investigated in vitro conditions by using diffusion disc method and the degree of inhibition on inoculum was determined through applying plant extracts that found effective to pathogen to seed before planting in the pot and field experiments. In the petri-experiments, nine plant species with antibacterial effects against the pathogen were identified. Three plant extracts (Allium sativum, Cistus creticus and Syzygium aromaticum) which showed the highest antibacterial effect in vitro experiments conducted by applicating of different doses; were investigated in terms of their impact on disease outbreak in pot and field experiments. These three plant extracts suppressed the disease in the pot experiment by %17-95, in the field experiment by %76-98. In this study, the most effective seed application was determined as Syzygium aromaticum. The extract suppressed the disease by 95% in pot experiments and 98% in the field experiments. In addition, Syzygium aromaticum extract had 5% germination enhancing effect. To conclude, the use of plant extracts as seed application in the integrated management of this disease has been considered as one of the successful management strategies.