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Introduction of biocontrol bacteria in potato rhizosphere to prevent latent contamination by pectinolytic bacteria and blackleg symptoms development

Amélie Beury: FN3PT/RD3PT

<div>To control and maintain at low level soil-borne pectinolytic bacteria naturally present in the soil microbiota and to minimize tuber infections, two combined biocontrol strategies for potato plants were developed. These strategies rely on the direct application in-furrow of two bacterial biocontrol agents that were <em>Pseudomonas putida</em> strain A14H7 exhibiting antibiosis activity (Raoul des Essarts <em>et al</em>, 2016) and <em>Rhodococcus erythropolis</em> strain R138 (Cirou <em>et al</em>, 2007) exhibiting a quorum-quenching activity. <em>R. erythropolis</em> R138 strain degrades quorum-sensing signal molecules of the N-acyl homoserine lactone class involved in virulence regulation in pectinolytic bacteria. The effect of this combined treatment on the acquisition of soil-borne pectinolytic bacteria by tubers and expression of blackleg symptoms on plants was evaluated. The two biocontrol agents were monitored over time in the soil rhizosphere during the growing period to ensure that they maintained at detectable levels. The field trials were conducted over three successive field generations. The results showed either an absence of tubers acquisition of pectinolytic bacteria or a decrease of blackleg symptoms in potato plants grown from treated soil. Our data suggest that this biocontrol strategy could provide significant protection of potato plants against pectinolytic bacteria under field conditions.</div>