Blue cornflower (Centaurea cyanus L.) as a component of agrocenosis: analysis of allelopathic mechanisms, agroecological consequences and control strategies

Abstract

This review presents an analysis of the results of experimental studies on the nature of the allelopathic interaction of cornflower (Centaurea cyanus L.) with winter agricultural crops. The purpose of the work was to summarize current knowledge on the biochemical mechanisms of phytotoxicity, allelochemicals of cornflower, agroecological consequences of weed infestation, and strategies for integrated control of cornflower in agrocoenoses. Differential crop sensitivity to cornflower allelochemicals was established in winter grain crops. In this regard, the phenomenon of hormesis was identified, where the action of low concentrations of aqueous leaf extract of cornflower (5–12 %) increased seed germination of grains by 8–16 %, while increasing to 25 % decreased it by 38–40 % compared with the control. Based on research results conducted in various countries, the profile of cornflower allelochemicals was found to include volatile organic compounds, phenolic acids (chlorogenic acid 15–45 mg/100 g dry weight), flavonoids (apigenin 10–30 mg/100 g), and anthocyanins. The phytotoxicity mechanisms of the complex of these compounds involve disruption of cell membrane permeability, inhibition of ATP synthesis in mitochondria, suppression of DNA topoisomerases, and activity of key glycolysis enzymes. Meanwhile, allelochemicals can spread through root exudates (concentration 100–500 μM in rhizosphere fluid), microbiological decomposition of residues, and gas diffusion of volatile compounds. It was also established that cornflower limits the impact on the rhizosphere microbiocenosis and demonstrates autotoxicity, inhibiting its own seed germination (by 15–22 % at densities exceeding 30–40 plants/m²). It was concluded that the allelopathic activity of cornflower can cause a yield reduction (up to 65 %) when exceeding the economic threshold of harmfulness (ETH) in agrocoenoses. Moreover, there is a problem of cornflower resistance to herbicides, as well as the phenomenon of enhanced allelopathic activity due to increased synthesis of phenolic compounds. Therefore, strategies for integrated control of cornflower in agrocoenoses of agricultural crops are recommended, including rotation of winter crops with spring crops to disrupt the cornflower life cycle; use of cover crops with allelopathic properties (barley, rye, sorghum), which suppress cornflower germination by 20–35 %; agronomic practices (delayed sowing, increasing the seeding rate by 15–25 %, alternating deep plowing with minimal tillage); and regular population monitoring.