Induction of resistance against Sclerotinia sclerotiorum in rapeseed by β-ocimene through enhanced production of coniferyl aldehyde

Rapeseed (Brassica napus) is an important oil resource, but its yield can be significantly compro-mised by Sclerotinia sclerotiorum (S. sclerotiorum) infection. Due to the lack of rapeseed strains that are highly or completely immune to S. sclerotiorum, enhancing rapeseed resistance through genetic approaches is challenging. Here, we developed a novel method to enhance rapeseed resistance to S. sclerotiorum using β-ocimene. The results showed that β-ocimene treatment significantly strength-ened defense capabilities of rapeseed. β-ocimene treatment can activate various defense-related signaling pathways, including jasmonic acid signaling, salicylic acid signaling, and MAPK sig-naling, in rapeseed and induce the accumulation of secondary metabolites coniferyl aldehyde, a core component of the phenylpropanoid pathway in plant defense response. Applying coniferyl al-dehyde to the leaves of rapeseed can remarkably enhance its resistance to sclerotinia disease. Col-lectively, these findings further clarify that β-ocimene activates the defense system of rapeseed, el-evates the content of coniferyl aldehyde, and thereby enables rapeseed to effectively resist sclero-tinia disease. In conclusion, we have not only uncovered the mechanism by which β-ocimene in-duces rapeseed resistance to sclerotinia disease but also provided a novel approach for the preven-tion and control of the harm caused by sclerotinia disease to rapeseed.