Evidence that the Biofungicide Serenade® (Bacillus subtilis) Suppresses Clubroot on Canola via Antibiosis and Induced Host Resistance.

Lahlali, R.L., Peng, G., Gossen, B.D., McGregor, L., Yu, F.Q., Hynes, R.K., Hwang, S.F., McDonald, M.R., and Boyetchko, S.M. (2013). "Evidence that the Biofungicide Serenade® (Bacillus subtilis) Suppresses Clubroot on Canola via Antibiosis and Induced Host Resistance.", Phytopathology, 103(3), pp. 245-254. doi : 10.1094/PHYTO-06-12-0123-R  Access to full text

Abstract

This study investigated how the timing of application of the biofungicide Serenade® (Bacillus subtilis QST713) or it components (product filtrate, bacterial cell suspension) influenced infection of canola by Plasmodiophora brassicae under controlled conditions. The biofungicide and its components were applied as a soil drench at 5% concentration (v:v or equivalent colony forming units) to a planting mix infested with P. brassicae at seeding and/or at transplanting 7 or 14 days after seeding (DAS) to target primary and secondary zoospores of P. brassicae. Quantitative PCR (qPCR) was used to assess root colonization by B. subtilis as well as P. brassicae. The biofungicide was consistently more effective than the individual components in reducing infection by P. brassicae. Two applications were more effective than one, with the biofungicide suppressing infection completely and the individual components reducing clubroot severity by 62–83%. The biofungicide also reduced genomic DNA of P. brassicae in canola roots by 26–99% at 7 and 14 DAS and the qPCR results were strongly correlated with root hair infection (%) assessed at the same time (r = 0.84–0.95). qPCR was also used to quantify the transcript activity of nine host-defense-related genes in inoculated plants treated with Serenade® at 14 DAS for potential induced resistance. Genes encoding the jasmonic acid (BnOPR2), ethylene (BnACO), and phenylpropanoid (BnOPCL and BnCCR) pathways were up-regulated by 2.2-23 fold in plants treated with the biofungicide relative to control plants. This induced defense response was translocated to the foliage (determined based on the inhibition of infection by Leptosphaeria maculans). It is possible that antibiosis and induced resistance are involved in clubroot suppression by Serenade®. Activity against the infection from both primary and secondary zoospores of P. brassicae may be required for maximum efficacy against clubroot.

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