Polyphenol metabolism of developing apple skin of a scab resistant and a susceptible apple cultivar

Abstract

During fruit development, the concentration of main polyphenols (flavonols, flavanols, dihydrochalcones, hydroxycinnamic acids, anthocyanins) and the activities of related enzymes (phenylalanine ammonia lyase, chalcone synthase/chalcone isomerase, flavanone 3-hydroxylase, dihydroflavonol 4-reductase, flavonol synthase, peroxidase) were monitored in apple (Malus domestica Borkh.). The seasonal survey was performed at five different sampling dates and included the healthy peel of the resistant cultivar 'Florina' and healthy peel, scab symptomatic spot and the tissue around the infected spot of the susceptible cultivar 'Golden Delicious'. From all enzymes tested, chalcone synthase/chalcone isomerase had the highest activity in both cultivars, while phenylalanine ammonia lyase had the lowest. The healthy peels of the susceptible and the resistant cultivar did not show differences in the accumulation of the main polyphenol groups present in the apple skin. However, in the resistant cultivar 'Florina', an increase of polyphenol enzyme activities could be observed in late stages of fruit development, which seems to be related to the anthocyanin accumulation in ripe fruits. Significant differences in the polyphenol metabolism were observed in the three different tissues of the susceptible cultivar 'Golden Delicious'. Increased concentrations of hydroxycinnamic acids, dihydrochalcones and flavan-3-ols were found in the scab symptomatic spots and surrounding tissues. Phenylalanine ammonia-lyase, dihydroflavonol 4-reductase, flavanone 3-hydroxylase and peroxidase showed higher activities in the scab symptomatic spot compared to other analysed tissues, whereas the activities of other enzymes remained unchanged. Highest induction of polyphenol accumulation after scab infection was observed in early developmental stages, whereas enzyme activities were increased in later stages.

Plant genotype and the preference and performance of herbivores: cultivar affects apple resistance to the florivorous weevil Anthonomus pomorum

“…The finding that the cultivar Florina was relatively more resistant than most other cultivars covered in the present study is in accordance with reports of high resistance of this cultivar to other pest insects such as aphids (Rat‐Morris, ; Qubbaj et al ., ; Dapena et al ., ), and particularly also to fungal and bacterial diseases such as apple scab Venturia inaequalis Wint. and fire blight Erwinia amylovora Winslow (Le Roux et al ., ; Slatnar et al ., ). It thereby emphasizes the need and possible opportunities for a better understanding of the basis of plant resistance to multiple biotic stresses (Stoeckli et al ., ; Smith & Clement, ; Seifi et al ., ).…”

Changes in phenolic content induced by infection with Didymella applanata and Leptosphaeria coniothyrium, the causal agents of raspberry spur and cane blight

“…The infected canes analysed in the present study contained higher levels of flavan‐3‐ols compared to healthy cane tissue. These results are in line with other studies (Mikulic Petkovsek et al ., ; Slatnar et al ., ), which report a higher content of flavan‐3‐ols in plant tissue triggered by different pathogen infections. According to some studies, an increased synthesis and accumulation of flavanols in plant tissues could be linked to their higher resistance (Leser & Treutter, ).…”

“…If pre-formed antifungal phenolics are not sufficient to stop the development of the infection process, plant cells usually respond by increasing the level of antifungal phenols at the infection site. It has been shown that some hydroxycinnamic acids, flavan-3-ols (epicatechin, procyanidin B1, catechin) and dihydrochalcones may be involved in the defence mechanism of apple leaves against the scab fungus Venturia inaequalis (Mikuli c Petkov sek et al, 2009;Slatnar et al, 2012). In general, an increase of levels of phenols was observed in infected leaf tissues compared to healthy tissues (Mikulic Petkovsek et al, 2011).…”

Variability of the phenolic profiles in the fruits from old, recent and new apple cultivars cultivated in Belgium

“…These complex biosynthetic pathways involve a series of enzymes, which have been, as well as the encoding genes, already functionally characterized in apple fruit (Khan et al 2012). The formation and activity of these enzymes are determined by the maturity stage, as well as internal (derived from genome differences) and several external (stress conditions existing before and after harvest) factors (Slatnar et al 2012). Therefore, studying the variation in the phenolic profiles engendered by genetic background apart from other influences is not feasible.…”