Herbicidal secondary metabolites from Bacillus velezensis JTB8-2 against Orobanche aegyptiaca.

Egyptian broomrape (Orobanche aegyptiaca) is a parasitic plants that cause significant losses to important crops. The effective methods for controlling this weed are rare. Biological control could be one of the possible strategies to tackle these weeds efficiently. In this work, a bacteria strain Bacillus velezensis JTB8-2 was proven to possesse biological control functions against broomrapes in both pot and field experiments. Four secondary metabolites (1-4) were isolated from the B. velezensis JTB8-2 crude extracts, and all of them could inhibit the germination of O. aegyptiaca seeds at concentrations from 0.5 mM to 4 mM. Their structures were further elucidated by Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) analysis. Among the isolated compounds, 1 and 2 exhibited the strongest herbicidal activity with 100% inhibition rate against the germination of O. aegyptiaca seeds at 4 mM, and thus had great potential in the development of new herbicidal products to control O. aegyptiaca in the future.