In healthy and in apple scab infected leaves and apple fruits, we determined the content of individual and total phenolics. The leaves were collected several times throughout the growing season and the fruits at technological maturity. In the leaves and fruit were detected hydroxycinnamic acids, flavan-3-ols, dihydrochalcones and flavonols, total phenolics and antioxidant capacity. The infection with scab caused significantly higher levels of individual and total phenolics in apple leaves as well as in the fruits.
The research dealt with phenolics in healthy versus scab infected apple leaves and fruits. The leaf samples were picked from May to September and the fruits at technological maturity. Infection with the Venturia inaequalis fungus enhanced the metabolism of phenolics at the infected sites, especially in the boundary tissue. Infected tissue showed in comparison to the healthy tissue up to 7.6 times more hydroxycinnamic acids, up to 2.9 times more flavan-3-ols and flavanols. The content of total phenolics in the infected tissue was 2.4 times higher than in the healthy leaves and fruit.
Phenolics were measured in leaves of apple cvs Jonagold and Golden Delicious, healthy and infected by Venturia inaequalis. Leaves were sampled from May to September 2005 and analyzed by HPLC. Phenolics detected were chlorogenic, caffeic, ferulic, p-coumaric, phloridzin, epicatechin, catechin, rutin and quercitrin. Total phenolics were determined with the Folin-Ciocalteu method. Infection by V. inequalis caused an accumulation of phenolics in infected leaves with up to 6.2- fold increase of flavonols, up to 6-fold increase of chlorogenic acid and up to 2.4-fold increase of the total phenolics.
Leaf samples were collected from apple varieties susceptible and resistant to apple scab (Venturia inaequalis) from June to September for 2 years. In the samples with the help of HPLC phenolics from the group of hydroxycinnamic acids and flavonoids were detected. During the growing season, the content of phenolic compounds changed and was related to the physiological stage of the tissue and cultivar. Each phenolic compound had its own curve of seasonal changes in concentration. Total phenols as well as single phenolics were statistically higher in resistant than in susceptible apple cultivars.
The aim of the study was to evaluate how the infection with apple scab influences the enzyme activity and the content of phenolics in apple peel. Infection with the Venturia inequalis fungus enhanced the metabolism of phenolics. The higest content of phenolics had infected and tissue around the spot, the lowest content had healthy peel. The highest enzyme activity for PAL, CHS/CHI, DFR, FLS were determined in scab spot. Scab spot showed in comparison to the healthy peel up to 3.4 times more hydroxycinnamic acids, up to 1.1 times more dihydrochalcones and up to 1.4 times more flavan-3-ols.