The effect and rate of anthracnose infection was evaluated on four French bean cultivars: ‘Paulista’ and ‘Berggold’ (tolerant), and ‘Top Crop’ 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. 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.
The chemical composition of dwarf French bean was compared among five production systems: conventional, integrated, organic, and biodynamic production systems and the control. Determination of sugars and organic acids was performed with a HPLC system, and identification of individual phenolic compounds using HPLC-MS. The chemical composition of the beans was unaffected by the production systems; however, the content levels of individual compounds were changed.
The effects of infection with Colletotrichum nymphaeae were studied on two strawberry cultivars: ‘Elsanta’ and ‘Honeoye’. Four treatments were established: (1) artificial inoculation; (2) spray application of pyraclostrobin + boscalid (Signum); (3) foliar spraying with calcium (Stopit); and (4) control (spraying with water). Sugars and organic acids as well as phenolic compounds were determined in strawberry fruit with the use of HPLC. Infected fruit accumulated large amounts of total sugars and low levels of organic acids. The contents of ellagic acid derivatives, flavonols, oligomeric procyanidins, flavan-3-ols, and total phenolics were highest in inoculated strawberry fruit. Results indicated that fungicide and calcium sprayings did not alter polyphenolic levels in plant tissue.
The effect of Colletotrichum simmondsii infection on the contents of sugars, organic acids, and individual phenolic compounds was investigated in strawberry cultivar ‘Clery’. Primary metabolites were determined with the use of HPLC and secondary metabolites further confirmed with HPLC-MS. Colletotrichum simmondsii caused a decrease in sucrose and an increase in fructose and glucose in strawberry fruit. A significant decrease in the content of malic and citric acids was recorded in infected fruit. Twelve forms of ellagic acid, nine flavanols and eight flavonols were identified in strawberry runners and nine forms of ellagic acid, six flavanols, seven flavonols and four anthocyanins in strawberry fruit. Significant differences in individual phenolic compounds in strawberry fruit were detected at the beginning of the infection compared to non-infected fruit. Specifically, ellagic acids significantly increased, flavonols generally decreased, and flavanols and anthocyanins increased with the progression of infection. Similarly, some forms of ellagic acid increased and others decreased in infected runners, procyanidins generally decreased and flavonols, increased but the differences were much less prominent.
Qualitative and quantitative changes of individual and total phenolics induced by Colletotrichum coccodesfungal infection have been studied in two sweet pepper cultivars ‘Soroksari’ and ‘Bagoly’, and the role of soluble phenolic compounds in plant's defence mechanism has been evaluated. Three distinct parts were analysed on pepper fruit: healthy tissue, anthracnose lesion, and bordering tissue, and individual phenolic compounds have been identified with the use of HPLC-MS system. In pepper fruit pericarp 21 phenolic compounds have been determined; the prevalent apigenin, quercetin and luteolin glycosides, chlorogenic acid and one chrysoeriol glucoside. C. coccodes infection increased the accumulation of chlorogenic acid, chrysoeriol glucoside, quercetin and luteolin glycosides in infected bordering tissue of both analysed pepper cultivars compared to healthy pepper tissue or symptomatic spot. Total apigenin derivatives did not show a significant increase in bordering tissue. This suggests a lesser role of apigenin glycosides in pepper plant defence against the Colletotrichum fungus.