Priming canola resistance to blackleg with weakly aggressive isolates leads to an activation of hydroxycinnamates

Abstract

Blackleg (Phoma leaf spot), caused by the ascomycete Leptosphaeria spp. (anamorph: Phoma lingam), is a serious yield-limiting factor in canola. Leptosphaeria spp. populations are highly diverse and display differential interactions with canola cultivars, ranging from hypersensitive-like reactions to partial resistance and susceptibility. Leptosphaeria biglobosa encompasses weakly aggressive isolates and can be found late in the season towards maturity stages of the crop while other isolates from Leptosphaeria maculans are highly aggressive and can be detected throughout the season. In an earlier study, we showed the primary involvement of lignin in the containment of the progress of Phoma leaf spot symptoms around the infection sites by comparing the reaction of three different cultivars with a set of isolates with various levels of aggressiveness. The present investigation reports on further characterization of the host responses to L. biglobosa and L. maculans isolates used individually or subsequently in the infection. Hydroxycinnamates were the major phenolics that differentially accumulated locally or systemically from the infection sites in response to either pre-or co-inoculation with the weakly aggressive isolate tested. Given the involvement of these hydroxycinnamates as precursors for the synthesis of lignin and phenylamide phytoalexins, their detected amounts in response to the priming with a weakly aggressive isolate could explain the restricted development of further inoculated highly aggressive isolates.Résumé : Le chancre noir (phoma), causé par l'ascomycète Leptosphaeria spp. (forme imparfaite : Phoma lingam), constitue un facteur limitant au rendement du canola. Les populations de Leptosphaeria spp. sont très diversifiées et montrent des interactions différentielles, variant de l'hypersensibilité à la résistance partielle ou la sensibilité, vis-à-vis des cultivars de canola. Leptosphaeria biglobosa se compose d'isolats peu agressifs qui n'apparaissent que tard dans la saison quand les plantes ont atteint leur maturité. Leptosphaeria maculans comporte des isolats très agressifs et peut être détecté durant toute la saison de production. Dans une étude précédente comparant les réactions différentielles de trois cultivars à une série d'isolats ayant des niveaux différents d'agressivité, nous avions montré le rôle de la lignine comme composante principale dans la restriction de la progression des symptômes de la maladie autour des sites d'infection. La présente étude fait davantage état de la caractérisation des réponses de l'hôte aux isolats de L. biglobosa et de L. maculans, inoculés soit séparément soit l'un après l'autre. Les dérivés hydroxycinnamiques sont les principaux composés phénoliques accumulés de manière différentielle, que ce soit localement autours des sites d'infection ou systémiquement, en réaction à la pré-ou à la co-inoculation avec l'isolat peu agressif étudié. Étant donné le rôle de ces dérivés hydroxycinnamiques comme précurseurs dans la synthèse de la lignine et de celle des phy...

Botrytis cinerea Manipulates the Antagonistic Effects between Immune Pathways to Promote Disease Development in Tomato

“…Further SA identity confirmation was performed using UPLC-MS/MS (El Hadrami and Daayf, 2009), and quantification was performed using HPLC. JA was extracted and analyzed using UPLC-MS/MS as described previously (Segarra et al, 2006).…”

Comparison of non-subjective relative fungal biomass measurements to quantify the Leptosphaeria maculans—Brassica napus interaction

“…The gene-for-gene interaction between avirulence genes in L. maculans and the corresponding resistance gene in B. napus is well-characterised (Ansan-Melayah et al [ 47 ]). Population studies on L. maculans characterise isolates into groups according to the virulence profile but little consideration is given to other traits that may characterise isolates, such as aggressiveness (West et al [ 7 ]; El Hadrami and Daayf [ 48 ]; Rouxel and Balesdent [ 49 ]). In the cotyledon inoculations in Experiment 3, differences in pathogen load were detected between the isolates, each of which was virulent towards the host lines in varying degrees depending on the cultivar.…”