Effects of withering time of fresh leaves on the formation of flavor quality of Taiping Houkui tea

Withering time of fresh leaves is a key factor affecting the stability of flavor quality of Taiping Houkui tea (TPHK). It's effect and mechanism on the formation of flavor in TPHK remain unelucidated. Here, metabolomics and transcriptomics were combined to comprehensively investigate changes in the main flavor compounds and the expression patterns of related genes under different withering times. The results showed that withering had the greatest influence on the content of most amino acids and aroma volatiles. The relative content of most volatiles was observed to be highest at 6–8 h of withering time, which was consistent with the results from the sensory evaluation of aroma quality. Plant hormone signal transduction pathways played a key role in the variation of the flavor compound content under different withering times, especially ABA and JA signals. WGCNA demonstrated that ABA, JA, IAA, SA and different flavor substances were significantly associated with specific modules. JA may be involved in the metabolism of theanine during withering, while ABA may be involved in the accumulation of aromatic amino acids and main aroma components of TPHK. This research may serve as a reference for the optimization of the processing technology for TPHK.