Integrated metabolic phenotypes and gene expression profiles revealed the effect of spreading on aroma volatiles formation in postharvest leaves of green tea

• VTs and FADVs were the main aroma compounds accumulated in green tea during spreading. • The degree of aroma accumulation promoted by moderate spreading was genotype dependent. • The aroma accumulation induced by spreading mainly derived from de novo synthesis rather than glycoside hydrolysis. • Two co-expression networks highly related to accumulation of aroma compounds were identified. Spreading is an indispensable process in the aroma formation of premium green tea. In this study, volatile metabolomics and transcriptomics were performed for three tea plant cultivars to investigate the mechanism of changes occurring in volatile compounds during green tea spreading. The content of primary aroma compounds significantly increased after spreading, the Wickremasinghe-Yamanishi ratio decreased and the Owuor’s flavor index increased with the extension of spreading time, and the degree of aroma production was genotype-dependent. Volatile terpenes and fatty acid-derived volatiles were the principal aroma volatiles that accumulated during the spreading of green tea, and the trends of their changes were consistent with the expression pattern of related synthesis pathway genes, indicating that they were primarily derived from de novo synthesis rather than glycoside hydrolysis. Two co-expression networks that were highly correlated with variations in the volatile component contents during the spreading process were identified via WGCNA. Our results provide insights into spreading that can be considered to improve the quality of green tea.