The impact of HvAACT1 gene conferring aluminium toxicity tolerance on barley yield in acid soils

Aluminium toxicity in acid soils is a major constraint to global crop production, particularly for cereal crops like barley, which are vital to food security. Although the HvAACT1 gene within the Alp QTL has been recognized as a key factor in aluminium tolerance through citrate secretion, its direct impact on barley yield under dynamic, real-world acidic conditions remains poorly understood. Most existing studies have focused on fixed pH levels, limiting insights into crop performance across the broader pH spectrum typical of acidic field conditions. In this study, we evaluated barley yield and agronomic traits across eight soil pH levels (4.0–4.8), using two near-isogenic lines (NILs): RGT Planet (acid soil susceptible) and P33–1 (acid soil tolerant, introgressed with Alp ). Our results demonstrate that P33–1 consistently outperformed RGT Planet, maintaining higher yield and better agronomic traits. Notably, yield reductions under acidic conditions were primarily driven by decreases in fertile tiller number and kernels per spike (P < 0.01), rather than changes in grain size or 1000-kernel weight, providing new insights into the physiological basis underpinning yield loss. By quantifying the complex relationship between soil pH and agronomic trait losses, our study delivers essential data that will inform crop modeling and advance breeding efforts for acid soil-tolerant varieties, contributing to more resilient and sustainable crop production in marginal soils worldwide. • First assessment of HvAACT1 effects on barley yield across realistic acid soil pH (4.0–4.8). • P33–1 (introgressed with the Alp QTL) shows higher yield and better agronomic traits than RGT Planet in acid soils. • Yield loss under acid soils is driven by fertile tillers and kernels per spike, not grain size. • Provides essential data for crop modeling and breeding acid soil-tolerant barley varieties.