Biocontrol of bacterial spot diseases of muskmelon using Paenibacillus polymyxa G-14

Paenibacillus polymyxa strain G-14 (PpG14) isolated from the muskmelon rhizosphere, produces antibiotic(s) that are active against Pseudomonas syringae pv. lachrymans and Acidovorax avenae subsp. citrulli (two pathogens that cause bacterial spot diseases). Strain G-14 strongly inhibited the growth of Pseudomonas syringae pv. lachrymans and Acidovorax avenae subsp. citruli in a dual-culture plate assay. The biocontrol activity of PpG14 was examined by pot and field tests. Results show that the strain significantly reduced the development and suppressed the incidence of bacterial spot diseases. Moreover, the prevention treatment was better than the therapy treatment when using this strain. Based on its main bacteriological properties, identification using VITEK 32 and analysis of the 16S rDNA gene sequence, showed that strain G-14 belonged to P. polymyxa . Optimal growth was studied; temperature and pH were 28°C and 7, respectively. Key words: Muskmelon, bacterial spot diseases, Paenibacillus polymyxa , biocontrol.