Isolation and identification of an endophytic bacteria Bacillus velezensis 8-4 exhibiting biocontrol activity against potato scab

Potato scab caused by Streptomyces is a serious soil-borne disease on potato. In this study, we isolated and screened an endophytic bacteria strain 8-4 from healthy potatoes. The strain 8-4 has a strong inhibitory effect on S. galilaeus and other five potato fungal pathogens. Based on morphological characteristics, 16S rDNA and gyrB gene sequence analyses, it was identified as Bacillus velezensis. Dual-culture test showed that the strain 8-4 not only inhibited the growth of S. galilaeus on potato, but also displayed inhibitory effects against four other potato pathogens, named Phoma foveat, Rhizoctonia solani, Fusarium avenaceum and Colletotrichum coccodes. It had the highest antagonistic activity against C. coccodes. In field experiments, the control efficiency of the strain 8-4 against potato scab reached 51.83 +/- 8.53% over other treatments including fungicide treatments. In addition, the yield of the potato treated with the strain 8-4 was 19.91 +/- 3.56% higher than those potatoes treated with other treatments. Thence, the endophytic bacteria B. velezensis 8-4 could be considered a potential biocontrol agent for potato scab.