Screening,identification and anti-microbial activity of antagonistic strains against potato dry rot

【Objective】To find out the antibacterial activity of strains from distiller's grain of highland barley against potato dry rot pathogen,so as to provide scientific basis for developing new biocontrol bacteria resources for biological control of potato dry rot.【Method】The activity of 40 strains of distiller's grains against the pathogen of potato dry rot (Qing 9A-7-5,Qing 9A-8-8,Qing 9A-5-3 and Qing 9A-6-2) was determined by plate confrontation method and the stability of the active strains was evaluated. The antibacterial activity and stability of active strains against potato dry rot pathogens were determined and evaluated through Oxford cup method. The active strain JZ1-1-1 was identified by morphological,physiological and biochemical and molecular biological methods.【Result】Eight strains with high antibacterial activity against potato dry rot pathogens,JZ2c24,JZ3d09,JZ3c08,JZ2b13,JZ1-4-10,JZ1-1-1. JZ1-1-9 and JZ1-4-1, were screened by the plate confrontation method from 40 strains of distiller's grains. Strain JZ1-1-1 had stable antibacterial activity against the pathogen Qing 9A-7-5,and the reduction rate of antibacterial band was 25.42%. Strain JZ1-1-9 had stable antibacterial activity against the pathogen Qing 9A-6-2,and its reduction rate of antibacterial band was 26.20%. When the concentration was 50 mg/mL,the fermentation liquid water phase extract solution of strain JZ1-1-1 had high antibacterial activity against the potato dry rot pathogen cyanobacteria 9A-7-5,and its moderate inhibitory concentration(EC₅₀) value was 19.16 mg/mL. The fermentation liquid water phase extract solution of strain JZ1-1-9 had higher antibacterial activity against potato dry rot pathogen cyanobacteria 9A-6-2,and its EC₅₀ value was 20.80 mg/mL. And the aqueous phase extract of the fermentation liquid of strain JZ1-1-1 was the most stable. According to results of colony morphological,physiological and molecular biochemical experiments,strain JZ1-1-1 was identified as Bacillus velezensis.【Conclusion】B. velezensis strain JZ1-1-1 from distiller's grain of highland barley has the potential to serve as potato preservation agent and biological antibacterialagent.