Upgrading the Potential of Biopesticide from Actinobacteria for Controlling Onion Bacterial Rots by Mixing two Identified Streptomyces species in Egypt

Abstract

Bacterial rots of onion are considered from the most dangerous stored and heaped onion crop diseases that cause huge loss in bulbs. Many bacterial species can induce onion bulb rots, with predominance of Pectobacterium carotovorum and Burkholderia cepacia that were used in this study. This research was conducted as an approach for improving the potential of biopesticide from actinobacteria in controlling onion bacterial rots by mixing Streptomyces coelicolor and Streptomyces lavendulae in one treatment against both P. carotovorum and B. cepacia each separately. The highest decrease in disease incidence was recorded in the mixed treatment of S. coelicolor and S. lavendulae that was recorded as 88.8% and 86.3% in case of P. carotovorum and B. cepacia, respectively, followed by the single treatment of S. lavendulae then the single treatment of S. coelicolor. Application of S. coelicolor and S. lavendulae, singly or in mixture had significantly increased the total phenols in onion bulbs but the highest increase was recorded in the mixed application treatment that recorded as 356.1% and 353.8% in case of P. carotovorum and B. cepacia, respectively. Also, the antioxidant enzymes (POX and PPO) activity was observed to be highest in case of the mixed treatment against both P. carotovorum and B. cepacia. On the otherhand lipid peroxidation was significantly decreased in all treatments but the highest decrease percentage was detected in the mixed treatment which was 53.3% and 57.7% in case of P. carotovorum and B. cepacia, respectively. Based on their efficiency and eco-safety, S. coelicolor and S. lavendulae have been recommended to be mixed in one treatment to increase the potential of biopesticide used for controlling onion bacterial rots.