Identification Of The Antagonistic Bacterial Strain18BS-12and Its Evaluation As A Biocontrol Agent Against Botrytis Cinerea

Gray mold caused by Botrytis cinerea can infect a variety of fruits and vegetables,frequently causing serious economic losses. The application of chemical pesticides hasbrought great harm to the ecological environment and human health. In this paper, a strainwith good control effect to B. cinerea was separated, screened and evaluated as a biocontrolagent against B. cinerea, to find new microbial pesticide resources to control B. cinerea. Themain results are as follows:1. A total of439actinomycetes strains and533bacteria strains were separated from51soil samples from Shaanxi, Gansu and Henan province by plate dilution method. The strain18BS-12showed good antagonistic effect to B. cinerea.2. Based on16S rDNA sequence analysis of18BS-12, the strain was identified asBurkholderia gladioli.3.18BS-12fermentation filtrate had obvious control effect equal to80%procymidone1000-fold diluent and40%pyrimethanil500-fold diluent on B. cinerea in detached leaves andpot experiment.4. The fermentation medium and fermentation conditions of18BS-12strain wereoptimized to improve its production rate of antifungal substances. The results indicated thatoptimal culture medium was2%cornmeal,1.5%beef extract, and0.005%FeSO4,respectively. The optimum fermentation condition was fermentation time120h, initial pH8.0,inoculation size3%，loading sample volume50mL, fermentation temperature32℃, rotatespeed180rpm, respectively.5. Some active substances of18BS-12fermentation filtrate were water-soluble and somewere liposoluble. Some proteins are also present in fermentation filtrate. Suchantagonistical materials showed strong stability to temperature, acids and bases, but wereunstable to petroleum ether and ultraviolet light.6.18BS-12fermentation filtrate could inhibit spore germination of B. cinerea, increasehyphae branch, decrease the number of hyphae and make hyphae become short and thick.7.18BS-12fermentation filtrate showed a wide inhibitory spectrum to Alternariabrassicae, Phytophthora capsici, Phomopsis vexans, Colletotrichum lagenarium, Fusarium oxysporum, Epicoccum nigrum, Fusarium proliferatum, Corynespora cassiicola andAlternaria solani.