Colletotrichum lindemuthianum infection causes changes in phenolic content of French green bean pods

•The synthesis of phenolics in healthy and anthracnose infected green bean pods.•Healthy tissue, anthracnose lesion, and bordering tissue were analysed on the pods.•Differences in the content of primary metabolites and individual and total phenolics.•After infection phenolics increased in bordering tissue and symptomatic spot.

The effect and rate of anthracnose infection was evaluated on four French bean cultivars: 'Paulista' and 'Berggold' (tolerant), and 'Topcrop' and 'Re dei Burri' (susceptible). Artificial inoculation with Colletotrichum lindemuthianum was performed and the infection rate assessed on technologically mature bean pods. Healthy tissue, symptomatic spot, and bordering tissue were analyzed. Primary and secondary metabolites were quantified with the use of HPLC and phenolics further identified with HPLC-MS-ESI. Fructose and glucose were the prevalent sugars in French bean pods, and malic acid the major organic acid identified in healthy tissue of all analyzed cultivars. The greatest infection rate was observed on green bean pods of the susceptible 'Top Crop' and 'Re dei Burri' cultivars. The infection rate of the 'Paulista' cultivar following artificial inoculation was only 0.8% which is indicative of its tolerance to the C. lindemuthianum fungus. Twenty five different phenolic compounds were determined and categorized in the following phenolic groups: hydroxycinnamic acid derivatives, flavan-3-ols, dihydrochalcones and flavonols. The content levels of all phenolic groups increased in bordering tissue and symptomatic spot after infection in all cultivars. Tolerant/resistant 'Paulista' and 'Berggold' cultivars were also characterized by higher content levels of flavan-3-ols (procyanidins and catechin), dihydrochalcones (phloretin, phloridzin) and specific flavonol glycosides.

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