Screening and Identification of Antagonistic Endophytic Bacteria Against Phytophthora drechsleri in cucumber

Abstract

【Objective】Endophytic bacteria with good resistance to Phytophthora were screened from cucumber leaves and identified, so as to provide experimental materials for further study of theoretical exploration and their application in controlling cucumber blight.【Method】Endophytic bacteria were screened from cucumber leaves, and were preliminarily screened according to microscopic characteristics, Gram staining reaction, colony arrangement and colony morphology. The antagonism of endophytic bacteria was tested by plate antagonism method and fermentation liquor antagonism method. Through 16S rDNA sequencing and homology analysis, phylogenetic tree was constructed to identify the target strains.【Result】Thirty-two endophytic bacteria were preliminarily screened and numbered as CL1-CL32, including 10 strains of Gram-negative bacillus, 13 strains of Gram-positive bacillus and 9 strains of Gram-positive cocci. Eight strains were found to have strong inhibitory effect on Phytophthora drechsleri by plate confrontation method, and the inhibition rate of mycelia ranged from 10.3% to 54.3%. The inhibition radius ranged from 1 mm to 7 mm. Three strains (CL7, CL9, CL15) with better inhibitory effect were tested in fermentation liquor antagonism experiment, and the inhibition rates were 54.4%, 72.2%, 63.3%, respectively.【Conclusion】The three endophytic bacteria (CL7, CL9, CL15) with strong inhibitory effect on P. drechsleri belonged to Pantoea sp., Pseudomonas sp., and Staphylococcus sp., among which CL9 belonging to Pseudomonas sp. had the most obvious inhibitory effect.

Keywords

• endophyte
• identification
• antagonism
• bacteriostasis rate of mycelium
• phytophthora drechsleri