Mass Spectrometry-Based Metabolic Profiling Reveals Small Molecules Associated with Physiological Resistance to Sclerotinia sclerotiorum in Dry Edible Bean.

Mass spectrometry (MS) based metabolic profiling is a powerful technique to identify new molecular targets for breeding tolerance to abiotic and biotic stresses. For dry bean (Phaseolus vulgaris L.), several Andean breeding lines have been identified to have partial physiological resistance (in contrast to field resistance) to white mold (Sclerotinia sclerotiorum). However the molecular basis of physiological resistance remains largely unknown. Here, mass spectrometry-based (UPLC-MS and GC-MS) metabolic profiling was conducted on leaf and stem tissue from plants inoculated with Sclerotinia. The analysis detected 144 metabolites that varied between lines A195 (resistant) and Sacramento (susceptible) among multiple time points relative to mock inoculation. The metabolites that varied in leaves and stems included amines, amino acids, saccharides, organic acids, phytoalexins, hormones, ureides, and molecules involved in cell wall and membrane composition. Additionally, proteomic profiling was conducted using tandem mass spectrometry (LC-MS/MS), and several proteins involved in primary metabolism were observed to vary among resistant and susceptible lines. Some of the biochemical pathways associated with resistance were consistent with changes to physiological components measured in leaves. The diversity in the observed metabolic changes points towards a multi-faceted mechanism for resistance to Sclerotinia in dry bean. The integration of physiological, metabolomic and proteomic data can be used to discover novel functional markers of resistance to white mold.