Trait-specific malting responses to different abiotic and biotic stress in barley; insights from trait-oriented meta-analysis

Barley ( Hordeum vulgare L.) is a cornerstone cereal for the malting and brewing industries, yet its grain quality is highly sensitive to environmental stress. In light of climate variability and rising pathogen incidence, it is essential to understand how diverse abiotic (e.g., drought, heat, waterlogging, nutrient deficiency) and biotic (e.g., pest infestation) stresses influence malting traits. This study employed a systematic meta-analysis of global experimental data to quantify stress-induced shifts in key malt quality parameters, including protein content, starch accumulation, beta-glucan concentration, free amino nitrogen (FAN), wort viscosity, and the Kolbach Index. The results revealed that malting traits respond in a highly stress-specific manner. For instance, FAN levels increased substantially under drought, waterlogging, heat, and pest stress, suggesting stress-enhanced nitrogen mobilization. The Kolbach Index rose under drought but declined under heat, indicating divergent proteolytic responses. Notably, reductions were found in beta-glucan content under drought (26.25%), heat stress (29.2%), and waterlogging (20%), contributing to improved lautering potential across stress scenarios. Wort viscosity also declined under most stress conditions except under heat, where it increased likely due to protein–carbohydrate complex accumulation. Starch content consistently decreased across all stress types, with the most severe losses observed under heat. These findings advance our understanding of the differential impacts of abiotic and biotic stresses on malting quality parameters and provide a robust evidence base for future studies investigating the physiological and biochemical mechanisms underlying stress-induced alterations in barley grain quality.