Prevalence of type III secretion system in effective biocontrol pseudomonads

Juliana Almario (1) , Davide Gobbin , Geneviève Défago , Yvan Moënne-Loccoz (1) , Fabio Rezzonico

1 LEM - Laboratoire d'Ecologie Microbienne - UMR 5557

Functional type III secretion system (T3SS) genes are needed for effective biocontrol of Pythium damping-off of cucumber by Pseudomonas fluorescens KD, but whether biocontrol Pseudomonas strains with T3SS genes display overall a higher plant-protecting activity is unknown. The assessment of 198 biocontrol fluorescent pseudomonads originating from 60 soils worldwide indicated that 32% harbour the ATPase-encoding T3SS gene hrcN, which was most often found in tomato isolates. The hrcN+ biocontrol strains (and especially those also producing 2,4-diacetylphloroglucinol and displaying 1-aminocyclopropane-1-carboxylate deaminase activity) displayed higher plant-protecting ability in comparison with hrcN− biocontrol strains, both in the Pythium/cucumber and Fusarium/cucumber pathosystems.

Mots clés: Type III secretion system; Biocontrol; Pseudomonas; 4-Diacetylphloroglucinol; ACC deaminase

Domaines: Biochimie, Biologie Moléculaire; Biologie végétale; Ecologie, Environnement; Biodiversité; Sciences agricoles; Toxicologie

Juliana Almario, Davide Gobbin, Geneviève Défago, Yvan Moënne-Loccoz, Fabio Rezzonico. Prevalence of type III secretion system in effective biocontrol pseudomonads. Research in Microbiology, 2014, 165 (4), pp.300-304. ⟨10.1016/j.resmic.2014.03.008⟩. ⟨hal-01010566⟩