Biofortification of plants with selenium (Se) is one of the current trends in agriculture. This treatment enriches plants with this essential element for humans and animals, and also increases plant resistance to stress factors. The current knowledge of the interactions between Se and plants is well documented but between the plants biofortificated with Se and phytophages is insufficient and this problem should be further investigated. The research has focused on the effect of the pre-treatment of pea with Se on the pea aphid feeding behaviour and demographic parameters of the aphid population, and also has shown the activity of antioxidant (superoxide dismutase and catalase), detoxifying (S-glutathione transferase and β-glucosidase) and redox (peroxidase and polyphenol oxidase) enzymes in tissues of Acyrthosiphon pisum. The analysis of feeding models recorded using the Electronic Penetration Graph technique has shown that the pre-treatment of peas with Se affects the activity of aphids during the feeding. The use of 10 and 20 µM sodium selenite and sodium selenate caused changes in A. pisum probing and feeding behavior. What is more, Se reduced the activity of aphids associated with the phloem phase and caused an extension of non-probing time and non-phloem penetration. The effect of Se on the demographic population parameters of the aphid was also observed in the significant reduction of female fertility and the reproductive potential of the insects. Selenium enrichment of plants colonized by aphids increased the activity of antioxidant, detoxifying and redox enzymes in the tissues of A. pisum. It was also found that both Se taken up by plants, as well as, the feeding of aphids resulted in greater synthesis of flavonols and carotenoids in pea leaves.

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Plant organisms are exposed to various biotic and abiotic stress factors, which cause oxidative stress consisting in the imbalance between the formation and removal of reactive oxygen species, causing damage to cell components. It has been observed that the accumulation of trace elements such as arsenic, cadmium, nickel, zinc and selenium is one of the plants defence strategies against phytophages and it is termed as Elemental Defence Hypothesis. Included in the trace elements, selenium is taken up from the soil by plants and included in their metabolism along sulphur transport and transformation pathways. This element in low concentration supports the resistance of plants to various stress factors by affecting the elements of the antioxidant system. Selenium contained in plants can also act on as a deterrent to phytophages or feeding them toxins and disrupting their development cycle.