Abstract
Metabolic changes in sorghum seedlings in response to Paenibacillus alvei (NAS-6G6)-induced systemic resistance against Fusarium pseudograminearum 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 P. alvei at a concentration of 1 × 108 colony forming units mL−1 prior to inoculation with F. pseudograminearum lowered crown rot disease severity significantly at the highest inoculum dose of 1 × 106 spores mL−1. 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 F. pseudograminearum. 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 F. pseudograminearum were observed between P. alvei-primed versus naïve S. bicolor 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 F. pseudograminearum.
Highlights
As an evolutionary adaptation to survive a sessile existence, in addition to pre-existing physical and chemical barriers, plants have developed the ability to actively protect themselves against environmental stress through the synthesis of complex and ever-changing mixtures of defence-related metabolites [1]
We investigated the protection offered by a Plant growth-promoting rhizobacteria (PGPR), P. alvei, in mitigating the disease susceptibility of sorghum seedlings towards F. pseudograminearum, the causative agent of crown rot disease
Priming S. bicolor seedlings with P. alvei NAS-6G6 resulted in the induction of systemic resistance against F. pseudograminearum
Summary
As an evolutionary adaptation to survive a sessile existence, in addition to pre-existing physical and chemical barriers, plants have developed the ability to actively protect themselves against environmental stress through the synthesis of complex and ever-changing mixtures of defence-related metabolites [1]. These metabolites can either be synthesised locally or systemically as part of systemic acquired resistance (SAR) [2,3]. It is hypothesised that in response to the negative ecological impact of SAR, evolutionary forces were directed towards the development of induced systemic resistance (ISR) [5]. During ISR, the plant is primed by beneficial microbes for an enhanced defensive response that only activates upon challenge with a stress, wasting no resources.
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