Abstract
<jats:p>The monograph presents a comprehensive biochemical analysis of the mechanisms underlying resilience of wheat and barley plants to fungal pathogens, primarily Fusarium spp. and Alternaria spp. The study integrates three key metabolic domains—phenylpropanoid metabolism, antioxidant responses, and lipid-based membrane remodeling—to establish a holistic model of plant defense functioning at early stages of plant development. The research addresses the urgent need for a deeper understanding of molecular determinants of resilience, given the significant economic and agroecological consequences caused by fungal infections in cereal crops. The primary objective of the study was to elucidate the interplay between structural, metabolic, and enzymatic defense pathways that collectively determine the degree of resistance in different genotypes. The research focused on identifying biochemical markers of resilience that can be used for differentiation between resistant and susceptible cultivars of wheat and barley. To achieve this, a wide spectrum of experimental approaches were applied, including determination of total phenolic content, analysis of antioxidant enzyme activity, determination of lipid fractions, assessment of fatty acid composition, and monitoring of the activity of key lipid-metabolizing enzymes such as phospholipase A2 and lipoxygenase. The methodological design enabled a detailed comparison of physiological and biochemical responses between resistant and susceptible genotypes at the action of phytopathogens and exogenic salicylic acid. The results revealed that resistant wheat genotypes exhibit a significantly higher activation of the phenylpropanoid pathway, including elevated activities of phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase, which collectively contribute to the strengthening of cell walls and enhanced antioxidant protection. Simultaneously, resistant cultivars maintained higher efficiency of the antioxidant system, as demonstrated by increased activity of catalase, peroxidase, glutathione reductase, and glutathione peroxidase, stabilizing reactive oxygen species level at the infection by phytopathogens. In barley, pathogen infection and salicylic acid treatment induced profound shifts in lipid composition and membrane structure. Resistant genotypes maintained a more favorable ratio of saturated to unsaturated fatty acids and demonstrated stronger activation of phospholipase A2 and lipoxygenase—enzymes crucial for lipid turnover and oxylipin-mediated signaling. The preservation of membrane fluidity and stability under infection by phytopathogens were identified as an important characteristics of resistance. The integration of the obtained results leads to the conclusion that resilience to Fusarium spp. and Alternaria spp. is a multifaceted trait driven by coordinated regulation of phenolic metabolism, antioxidant defense, and lipid remodeling. These pathways collectively form a dynamic system of structural and metabolic responses that ensure effective adaptation to fungal phytopathogens. The findings provide a robust biochemical foundation for developing diagnostic markers of resistance and may serve as valuable tools for breeding programs aimed at creating cereal cultivars with enhanced resilience to fungal pathogens.</jats:p>