Abstract:
Plants defend themselves from pathogens by producing bioactive defense chemicals.
The biochemical mechanisms relating to quantitative resistance of potato to root infection by
Spongospora subterranea f. sp. subterranea (Sss) are, however, not understood, and are not e ciently
utilized in potato breeding programs. Untargeted metabolomics using ultra-performance liquid
chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was
used to elucidate the biochemical mechanisms of susceptibility to Sss root infection. Potato roots and
root exudate metabolic profiles of five tolerant cultivars were compared with those of five susceptible
cultivars, following Sss inoculation, to identify tolerance-related metabolites. Comparison of the
relative metabolite abundance of tolerant versus susceptible cultivars revealed contrasting responses
to Sss infection. Metabolites belonging to amino acids, organic acids, fatty acids, phenolics, and sugars,
as well as well-known cell wall thickening compounds were putatively identified and were especially
abundant in the tolerant cultivars relative to the susceptible cultivars. Metabolites known to activate
plant secondary defense metabolism were significantly increased in the tolerant cultivars compared
to susceptible cultivars following Sss inoculation. Root-exuded compounds belonging to the chemical
class of phenolics were also found in abundance in the tolerant cultivars compared to susceptible
cultivars. This study illustrated that Sss infection of potato roots leads to di erential expression of
metabolites in tolerant and susceptible potato cultivars.
