Metabolomic Profiling to Characterize the Defense Response of Sugar Beet during Rhizoctonia solani Interactions

Sugar beet can be significantly impacted by Rhizoctonia crown and root rot caused by Rhizoctonia solani AG 2-2 IIIB.  The molecular processes that mediate compatible and incompatible sugar beet interactions with R. solani are largely unknown and identifying the metabolites associated with R. solani infection may provide evidence for important biological pathways involved with resistance.  The metabolic changes that occurred during susceptible and resistant R. solani interactions were compared with mock inoculated treatments and characterized using a non-targeted metabolomics workflow spanning primary and secondary metabolism products.  Metabolites were extracted from infected and healthy, root and leaf tissue at multiple time points to best reflect the R. solani infection process and analyzed using both UHPL-MS and GC-MS.  Statistical interrogation of the datasets revealed clear distinction between tissue type and genotype, and more subtle changes in response to inoculation that was dependent on genotype.  UHPLC-MS was more sensitive than GC-MS, and therefore more secondary metabolites including several phytolexins, terpenes, and alkaloids, were identified.  Several biochemical pathways appear to be involved during susceptible and resistant interactions with R. solani, and indicate a complex role of primary and secondary metabolites in sugar beet during fungal interactions.