Identification of Volatile and Non-Volatile Components in Taiping Houkui Tea Made from ‘Shidacha’ and Non-‘Shidacha’ Tea Varieties and Phylogenetic Analysis

Taiping Houkui green tea is mainly made from the young shoots of the sextual tea line ‘Shidacha’. In the present study, the differences in the quality and genetic evolution of green tea made from the young shoots of five ‘Shidacha’ varieties (Gaojiazao, Huangzhong, Shidacha No.2, Shidacha No.6, and Guangyangzao) and two non-‘Shidacha’ tea varieties (Fuzao No.2 and Shuchazao) were explored. The volatile and non-volatile metabolites of the seven tea samples were analyzed, and the differences in genome-wide transcriptional levels and genetic background among the seven tea varieties were analyzed using RNA sequencing (RNA-seq). No significant differences in catechin content or the total content of free amino acids were found among all tea samples except Shuchazao, whereas caffeine content differed significantly among all samples. The contents of floral aroma compounds such as linalool, linalool oxide, geraniol and jasmone were relatively high in the infusion of ‘Shidacha’ green tea. RNA sequencing results showed that the genome-wide transcriptional level of Guangyangzao was close to that of the non-‘Shidacha’ tea varieties. In principal component analysis (PCA), Guangyangzao and the other ‘Shidacha’ varieties were distributed in different quadrants. Phylogenetic analysis showed that the non-‘Shidacha’ tea varieties had a close genetic relationship with each other as well as Gaojiazao and Huangzhong, but was far away from the other ‘Shidacha’ varieties. The transcriptional levels of most of the key enzyme genes involved in the biosynthesis of linalool, indole, nerolidol and jasmone lactone were higher in the ‘Shidacha’ tea varieties than in the non-‘Shidacha’ ones. This study provides important theoretical support for the breeding of excellent ‘Shidacha’ varieties and provides a theoretical basis for follow-up research on the formation mechanism of floral aroma compounds in tea leaves.