Effective control of sclerotinia stem rot in canola plants through application of exogenous hairpin RNA of multiple S. sclerotiorum genes.

Sclerotinia stem rot (SSR) is a globally destructive plant disease caused by Sclerotinia sclerotiorum . Current management of SSR primarily relies on chemical fungicides and crop rotation, raising environmental concerns. In this study, we developed an eco-friendly RNA bio-fungicide targeting S. sclerotiorum . Six S. sclerotiorum genes were selected for dsRNA synthesis. Four genes, including a Chitin binding domain (CBD), Mitogen-activated protein kinase (MAPK), oxaloacetate acetylhydrolase (OA), and Abhydrolase-3 (Abh), were combined to express hairpin RNA in E. coli HT115. Application of total RNA extracted from E. coli HT115 expressing hairpin RNA on disease progressive and necrosis lesion was evaluated. Gene expression analysis using real-time PCR showed silencing of the target genes using 50 ng/µl of dsRNA in a fungal liquid culture. Detached leaf assay and greenhouse application of dsRNA on canola stem and leaves showed variation in the reduction of necrosis symptoms by dsRNA of different genes, with Abhydrolase-3 being the most effective. The dsRNA from a combination of four genes reduced disease severity significantly (P = 0.01). Plants sprayed with hpRNA from four genes had lesions that were almost 30% smaller than that of plants treated with Abh alone, in lab and greenhouse assays. Results of this study highlight the potential of RNAi to manage diseases caused by S. sclerotiorum ; however, it also shows that additional research is necessary to optimize its efficacy.