[Screening, identification, and biocontrol effect of antagonistic bacteria against Phytophthora capsici]

A total of 98 isolates with antagonistic activity against Phytophthora capsici were isolated from the rhizosphere soil of healthy pepper plants in the fields seriously infected by pepper Phytophthora capsicit, and two strains named as HL-3 and LZ-8 were screened, which had the characteristics of wide-spectrum antagonism and good growth under poor soil condition. The HL-3 and LZ-8 were identified as Paenibacillus polymyxa and Bacillus pumilus, respectively, based on their morphological and biochemical characteristics and 16S rDNA sequences. The two strains could inhibit the mycelium growth of P. capsici, and the inhibitory effect of HL-3 and LZ-8 was 72% and 68%, respectively. The two strains also had antifungal activities toward other plant pathogens such as Verticillium dahliae, Fusarium oxysporum f. sp. cucumerinum, F. oxysporum f. sp. vasinfectum, Rhizoctonia solani, Phtophthora parasitica var. nicotiana, and Ralstonia solanacearum. Pot experiment showed that the biocontrol effects of HL-3 and LZ-8 against P. capsici at the seedling stage of pepper were 72% and 83%, respectively, and both of the strains had significant growth-promoting effect on pepper plants.