Spinach flavonoid-rich extract: Unleashing plant defense mechanisms against cucumber powdery mildew

Abstract

In response to the escalating demand for organic commodities, the exploration of non-chemical alternatives such as phytochemicals for plant disease management has gained momentum. This investigation focused on assessing the efficacy of a sustainable compound, Spinach Flavonoid-Rich Extract (SFRE), in mitigating cucumber powdery mildew (Podosphaera fusca) under controlled greenhouse conditions, and its potential in eliciting plant defense mechanisms at both biochemical and genetic levels. The application of SFRE resulted in a significant reduction in P. fusca disease severity, with a decrease of approximately 99%. High-Performance Liquid Chromatography (HPLC) analysis identified spinacetin as the dominant flavonoid in SFRE, with a concentration of 81.97 μg per 100 mg of the extract's dry weight. Furthermore, SFRE was found to induce systemic resistance in the infected seedlings, as evidenced by the upregulation of defense-related enzymes, including β-1,3-glucanase, chitinase, peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase, and the enhanced expression of β-1,3-glucanase, chitinase, and phenylalanine ammonia-lyase genes. In addition, SFRE application led to an accumulation of flavonoid/phenolic compounds and an enhancement in chlorophyll synthesis. A robust correlation was observed between phenolic compounds and the activities of defense enzymes, as well as the expression of the tested genes. This study substantiates that SFRE, as a reservoir of natural compounds, presents an effective and environmentally friendly alternative to chemical fungicides for P. fusca control, and could be incorporated into a comprehensive approach to managing cucumber powdery mildew through integrated disease management strategies.