Synergistic effects of pre-harvest drought and shade on flavor and aroma enhancement in fermented tea: Insights into JA/ABA signaling and metabolic regulation.

Drought stress during summer significantly impairs tea quality. This study is the first to systematically investigate the combined effects of pre-harvest drought and shade treatments on flavor and aroma compounds' spatial and temporal regulation during black and white tea processing. Through physiological and biochemical analyses, HPLC, electronic tongue analysis, and HS-SPME-GC-MS, we found that drought+shade (D + S) treatment significantly increases free amino acids and theaflavin levels, thereby enhancing umami, aftertaste, and richness. Using the OAV method, we identified 18 key volatiles, including benzyl alcohol, phenylethyl alcohol, linalool, (Z)-linalool oxide (furanoid), dehydrolinalool, benzaldehyde, and β-ionone, which contribute to floral and fruity flavors in the D + S group. Gene expression assays revealed that jasmonic and abscisic acid signaling pathways activated the aroma accumulation in the D + S group. This study elucidates the synergistic regulation of metabolic transformations by pre-harvest drought and shade, providing a theoretical foundation for optimizing tea plantation management under adverse conditions.