CHARACTERIZATION OF APOPLAST-COLONIZING ENDOPHYTES FROM OILSEED RAPE LEAVES SHOWING ANTAGONISM TO CANOLA PHYTOPATHOGENS

FM ROMERO; FR ROSSI; ANDRÉS GÁRRIZ; OA RUIZ

Barcelona

Congreso; XXII Congreso de la Sociedad Española de Fisiología Vegetal; 2017

Many endophytic bacteria colonize host tissues internally without causing damage or eliciting diseasesymptoms and in some cases promote plant growth and protect them against pathogens. This work aimedto characterize bacterial members of the apoplast-colonizing community of oilseed rape plants grownunder conditions of commercial production, and to analyze their antagonistic properties againstphytopathogens. Several bacterial endophytes were isolated from the apoplast of field-grown oilseed rapeleaves. These isolates were co-cultured with different canola pathogens, such as the fungal pathogensLeptosphaeria maculans and Sclerotinia sclerotiorum and the bacterial pathogen Xanthomonascampestris, in order to evaluate their antagonistic properties in vitro. In this way, three isolates (Apo8,Apo11 and Apo12) were selected based on their ability to inhibit all pathogens tested in vitro. Theseisolates were identified by sequencing the ARNr 16S gene as members or the genus Pseudomonas,specially related to the specie P. viridiflava. In order to test these isolates for their ability to diminish theinfection provoked by X. campestris, oilseed rape seeds were inoculated with bacterial endophytes andfour weeks after sowing these plants were challenged with X. campestris.Thus, plants inoculated withApo11 showed a decreased pathogen propagation in comparison to mock-inoculated ones. Moreover,Apo11-inoculation induces the expression of defense genes involved in the salicylic acid and jasmonatessignaling pathways. In addition to that, Apo11 inoculation produced a 50%-increment in fresh and dryweight of oilseed rape plants. This work allowed the identification of bacteria from apoplast of oilseed rapeleaves able to inhibit growth of pathogens in vitro and to reduce disease symptoms caused by X.campestris when inoculated on canola plants. These features, along with their potential for plant growthpromotion, render the above-mentioned isolate an interesting candidate for the development of biologicalformulations for growth promotion and control of canola diseases.