Impact of Aphis fabae Scopoli Infestation on Biochemical and Physiological Stress Markers in Faba Bean (Vicia faba L.)

Vicia faba is an agriculturally and nutritionally important legume whose growth and productivity are strongly influenced by biotic stress factors. Understanding the mechanisms by which plants respond to stress is therefore essential for improving agricultural productivity and enabling the selection of stress-tolerant cultivars. This study evaluated whether biochemical and physiological parameters can serve as early indicators of stress induced by Aphis fabae infestation in young V. faba plants. Plants were exposed to two levels of aphid infestation (low- and high-stress) and compared with aphid-free controls. Low stress caused minimal alterations in antioxidant responses: catalase (CAT) activity increased by 9.9%, glutathione (GSH) content by 20%, and malondialdehyde (MDA) levels decreased by 17.6% relative to controls. Under high stress, oxidative damage and antioxidant activation were pronounced, with CAT activity rising 2.4-fold, GSH content increasing 2.6-fold, and MDA accumulating 2.6-fold compared to control plants. Superoxide dismutase (SOD) activities increased under both stress levels, though without large differences, while nitrate reductase (NR) activity showed non-significant variation. Proline accumulation remained largely unchanged, showing only a slight 13–15% increase relative to controls. Photosynthetic pigment analysis revealed that low stress reduced contents of chlorophyll a and total chlorophyll, while increasing contents of chlorophyll b and carotenoids. Stress markedly altered pigment balance, yielding a 25.4% higher chlorophyll a/b ratio compared with control plants. The results indicate that V. faba plants can tolerate low-intensity aphid stress with minimal biochemical disturbance, whereas high infestation elicits strong oxidative stress and significant physiological changes. The measured biochemical markers, particularly CAT, MDA, and GSH, proved sensitive to early stress onset, offering valuable tools for early detection of biotic stress before visible symptoms appear. The research contributes to a better understanding of plant responses to stress, enables early detection of stress factors affecting plant physiology, facilitates the assessment of their adaptive potential, and may aid in the development of strategies to improve faba bean resistance to pest infestations. This research enhances understanding of V. faba stress responses, enabling early detection of stress factors and assessment of the plant’s adaptive potential. The insights gained may support the development of strategies to improve faba bean resistance to pest infestations and contribute to more sustainable agricultural productivity.