Metabolomic profiles associated with physiological resistance to Sclerotinia sclerotiorum (Lib.) de Bary in common bean

Abstract

Common bean (Phaseolus vulgaris L.) is an important global food crop with a recently sequenced and annotated genome. Plant metabolic and hormone processes are being increasingly recognized as central to disease resistance. For common bean, the molecular and metabolic processes that mediate resistance to white mold disease (caused by Sclerotinia sclerotiorum, (Lib.) de Bary) are largely unknown. Identifying metabolites associated with Sclerotinia infection may provide novel targets to breed for enhanced resistance. The metabolic changes that occur during S. sclerotiorum infection of a detached leaf were characterized using a non-targeted metabolomics workflow spanning primary and secondary metabolism, and a targeted panel of 13 hormones. Partial resistant (A195, beige seed coat color) and susceptible (Sacramento, light red kidney market class) Andean bean lines were inoculated with isolate S20 for non-targeted metabolite profiling at 16, 24, and 48 hours post inoculation (hpi) and at 8 and 16 hpi for hormones. Metabolites from healthy tissue adjacent to the necrotic lesion were extracted with the solvent methanol:water (80:20) and detected using non-targeted UPLC-TOF-MS and GC-MS workflows, and hormones were profiled using UPLC-MS/MS. The analysis detected 140 metabolites that varied between A195 and Sacramento, with the greatest metabolite variation occurring at 16 hpi. The metabolites that varied included amines, amino acids, saccharides, organic acids, phytoalexins, hormones, ureides, and molecules involved in cell wall and membrane composition. The diversity in observed metabolic changes points towards a multi-faceted response associated with plant resistance to S. sclerotiorum in common bean. The integration of metabolomics and genomic data discover functional markers of metabolic resistance to white mold.