| Summary: | Metabolic changes in sorghum seedlings in response to <i>Paenibacillus alvei</i> (NAS-6G6)-induced systemic resistance against <i>Fusarium pseudograminearum</i> crown rot were investigated by means of untargeted ultra-high performance liquid chromatography-high definition mass spectrometry (UHPLC-HDMS). Treatment of seedlings with the plant growth-promoting rhizobacterium <i>P. alvei</i> at a concentration of 1 × 10<sup>8</sup> colony forming units mL<sup>−1</sup> prior to inoculation with <i>F. pseudograminearum</i> lowered crown rot disease severity significantly at the highest inoculum dose of 1 × 10<sup>6</sup> spores mL<sup>−1</sup>. Intracellular metabolites were subsequently methanol-extracted from treated and untreated sorghum roots, stems and leaves at 1, 4 and 7 days post inoculation (d.p.i.) with <i>F. pseudograminearum</i>. The extracts were analysed on an UHPLC-HDMS platform, and the data chemometrically processed to determine metabolic profiles and signatures related to priming and induced resistance. Significant treatment-related differences in primary and secondary metabolism post inoculation with <i>F. pseudograminearum</i> were observed between <i>P. alvei</i>-primed versus naïve <i>S. bicolor</i> seedlings. The differential metabolic reprogramming in primed plants comprised of a quicker and/or enhanced upregulation of amino acid-, phytohormone-, phenylpropanoid-, flavonoid- and lipid metabolites in response to inoculation with <i>F. pseudograminearum</i>.
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