Biocontrol factors analysis of moderate halophilic bacterium S61 and its control effect on potato dry rot

【Objective】The inhibitory activity and control effect of moderate halophilic bacteria S61 against pathogenic fungi of potato dry rot was determinedto provide a scientific basis for the biological control and green prevention and control of potato dry rot.【Method】A moderately halophilic strain S61 from Qarhan Salt Lake in Qinghai was used as material and was was identified by morphology, physiological and biochemical characteristics and molecular biology methods. The inhibitory activity of strain S61 and its organic solvent extract from fermentation against potato dry rot pathogens and the safety assessment were determined by confrontation culture method and potato experiment in vivo. The capacity of producing lipopeptides and proteins of strain S61' s fermentation was determined by transparent circle and oil drain ring methods.【Result】Combining the morphological characteristics, physiological and biochemical characteristics and phylogenetic tree analysis results, the strain S61 was identified as Halobacillus trueperi. Its fermentation could produce protease, amylase, cellulose, and lipopeptides. S61 and its organic solvent extract had different inhibitory activities against 3 potato dry rot pathogenic fungi(Qing 9A-4-13, Qing 9A-5-2 and 65B-2-6). S61 had the highest inhibitory activity against pathogen Qing9A-4-13, with an inhibition rate 55.67%(7 d). Its N-butyl alcohol extract at the different concentrations(1, 5, 10 and 20 mg/mL) had the highest inhibitory activity against pathogen Qing 9A-4-13, with inhibition rates 61.50%, 63.00%, 64.00% and 66.00%, respectively. The strain S61 and its N-butyl alcohol extract were safe for potato in storage.【Conclusion】The moderate halophilic bacterium S61 has inhibitory activity against potato dry rot pathogenic fungi both in vitro and in vivo. The N-butyl alcohol extract has the highest inhibitory activity. It has biocontrol factors and could produce metabolic products with anti-fungi activity. It proves that S61 has good biocontrol potential in potato dry rot.