Biocontrol and plant growth promotion potential of endophytic JY-7-2L on Debx.

Debx. is a famous medicinal plant rich in alkaloids and widely used to treat various human diseases in Asian countries. However, southern blight caused by severely hampered the yield of . Beneficial microbe-based biological control is becoming a promising alternative and an environmentally friendly approach for the management of plant diseases. In this study, we evaluated the biocontrol potential of an endophytic bacterial strain JY-7-2L, which was isolated from the leaves of , against southern blight and by a series of field experiments. JY-7-2L was identified as based on multi-locus sequence analysis. JY-7-2L showed strong antagonistic activity against and on root slices by dual-culture assay. Cell-free culture filtrate of JY-7-2L significantly inhibited the hyphal growth, sclerotia formation, and germination of . In addition, volatile compounds produced by JY-7-2L completely and directly inhibited the growth of . Furthermore, JY-7-2L was proved to produce hydrolytic enzymes including glucanase, cellulase, protease, indole acetic acid, and siderophore. The presence of , , , , , and genes by PCR amplification indicated that JY-7-2L was able to produce antifungal lipopeptides and polyketides. Field trials indicated that application of the JY-7-2L fermentation culture significantly reduced southern blight disease severity by up to 30% with a long-acting duration of up to 62 days. Meanwhile, JY-7-2L significantly promoted the fresh and dry weights of the stem, main root, and lateral roots of compared to non-inoculation and/or commercial product treatments. Taken together, JY-7-2L can be used as a promising biocontrol agent for the control of southern blight in .