Comparative analysis of Quercus suber L. acorns in natural and semi-natural stands: Morphology characterization, insect attacks, and chemical composition

The present study aims to investigate the differences between cork oak acorns from natural and semi-natural stands in terms of morphology, insect attack rate, and acorn chemical composition. Moreover, it examines the metabolic responses induced by insect attacks. The results show that acorns from the semi-natural stand in our study are larger than those from the natural stand. In addition, the insect attack rate was higher in the natural stand (8.25%) than in the semi-natural stand (6.25%). Furthermore, acorns in the semi-natural stand exhibit high total flavonoid content (TFC), whereas those in the natural stand are rich in total phenolic content (TPC). In terms of biochemical changes in acorns, the study revealed a remarkably significant difference in TPC, TFC, and antioxidant activity subsequent to infestation by Cydia and Curculio insects. Cydia-infested acorns from the natural stand had higher TPC levels, with a value of 93.96±0.39 mg GAE/g, showing a 17.7% increase over healthy acorns. Acorns from the semi-natural stand attacked by Curculio show the highest TFC with a value of 0.288±0.004 mg EQ/g, showing a 121.5% increase over healthy acorns. Moreover, both DPPH and FRAP methods revealed that antioxidant activity of the acorns from the semi-natural stand attacked by Curculio was more effective. This research is crucial for providing a solid foundation for the selection of high-quality cork oak germplasm resources and exploring the potential valorization of insect-affected acorns in the realms of food and agriculture.