Abstract: To screen the antagonistic endophytic bacteria against Gloeosporium theae-sinensis Miyake, the healthy leaves of tea plants were utilized as materials, and the plate antagonistic method was used. The isolated bacteria were identified and evaluated for antimicrobial efficacy. The culture conditions were optimized using response surface methodology. One antagonistic bacterium X13 was screened from 162 strains of endophytic bacteria isolated, which had a good inhibitory effect on Colletotrichum gloeosporioides. The strain X13 was identified as Bacillus subtilis through morphological observation, physiological and biochemical tests, and 16S rDNA phylogenetic analysis. The inhibitory rate of strain X13 on the mycelial growth of C. gloeosporioides reached 61.6%. The logarithmic growth was between 2-14 h. The optimal culture conditions were 4.0% (mass percentage concentration) corn flour, 1.0% (mass percentage concentration) NaNO₃, and 3.5% (volume fraction) inoculation. This study laid a key theoretical foundation for the prevention of the tea pathogen G. theae-sinensis and the development of its biocontrol agents.

Key words: tea plant, Gloeosporium theae-sinensis, endophytic bacteria, Bacillus subtilis, culture condition