Abstract:

The antagonistic strains against bacterial fruit blotch（BFB）of cantaloupe were screened from soil, their taxonomic status was clarified, and their growth conditions and disease prevention effects were determined. Separation and screening were carried out by plate dilution method and confrontation method, and the species was identified by comprehensive morphological, physiological, biochemical and molecular identification. After determining the species of biocontrol bacteria, the optimal growth conditions were determined, and the bacteriostatic effect was determined by the plate confrontation method. The leaves and potted plants of biocontrol bacteria were measured by acupuncture inoculation method and foliar spraying method respectively. In this study, 196 strains of bacteria were isolated from soil samples, 20 strains of them were found to have bacteriostatic effect via confrontation method. Among them, two strains numbered 131 and 791 had better plate antagonism effect on the pathogen of BFB, and the diameters of the inhibition zones were（19.03±0.13）mm and（17.55±0.29）mm, respectively. The strain 131 was identified as Bacillus safensis and strain 791 as B. velezensis. The optimal growth condition of strain 131 was NB medium, cultured for 18 h, temperature was 37℃, pH 7 and the inoculum was 2%. The optimal growth condition of strain 791 was KB medium, cultured for 18 h, temperature was 37℃, pH 6 and the inoculation amount was 1%. Strain 131 and 791 were 83.33% and 87.53% in vitro, 69.86% and 77.99% in indoor pots, respectively; meanwhile they had inhibitory effects on various pathogens. In summary, strain 131 and 791 are Bacillus with good control effect on BFB, which provides theoretical supplements for the prevention and control of BFB and lays a solid foundation for BFB.

Key words: bacterial fruit blotch of cantaloupe, antagonism, identification, control effect on potted plant, bacteriostatic effect, optimal growth conditions