The needles of Taxus species contain a large number of bioactive compounds, such as flavonoids. In the present study, the total flavonoid content in leaves of Taxus media and Taxus mairei was 19.953 and 14.464 mg/g, respectively. A total of 197 flavonoid metabolites (70 flavones, 42 flavonols, 26 flavone C-glycosides, 20 flavanones, 15 anthocyanins, 13 isoflavones, 6 flavonolignans, and 5 proanthocyanidins) were identified for the first time by a widely targeted Ultra Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry (UPLC-ESI-MS/MS) method within the two Taxus species, containing 160 common metabolites, with 37 unique metabolites merely determined in T. mairei or T. media. Moreover, 42 differential flavonoid metabolites were screened in the two Taxus species, which showed specific metabolic patterns in isoflavonoid biosynthesis, anthocyanin biosynthesis, and flavone and flavonol biosynthesis pathways. Compared to T. mairei, a more activated phenylpropanoid pathway was found in T. media, which could be responsible for the higher content of total flavonoids in T. media. Our results provide new insights into the diversity of flavonoid metabolites between T. mairei and T. media, and provide a theoretical basis for the sufficient utilization of Taxus species and the development of novel drugs.

Leaf scorch exists as a common phenomenon in the development of plant, especially when plants encounter various adversities, which leads to great losses in agricultural production. Both Jinhong poplar (JHP) and Caihong poplar (CHP) (Populus deltoids) are obtained from a bud sport on Zhonghong poplar. Compared with CHP, JHP always exhibits leaf scorch, poor growth, premature leaf discoloration, and even death. In this study, the candidate genes associated with leaf scorch between JHP and CHP were identified by the whole genome resequencing using Illumina HiSeqTM. There were 218,880 polymorphic SNPs and 46,933 indels between JHP and CHP, respectively. Among these, the candidate genes carrying non-synonymous SNPs in coding regions were classified into 6 groups. The expression pattern of these candidate genes was also explored in JHP and CHP among different sampling stages. Combined with the qRT-PCR analysis, the results showed that genes associated with transport of various nutritional elements, senescence and MYB transcription factor might play important roles during the process of leaf scorch in Populus deltoids. Four genes belonging to these three groups carried more than three SNPs in their coding sequence, which might play important roles in leaf scorch. The above results provided candidate genes involved in leaf scorch in Populus deltoids, and made us better understand the molecular regulation mechanism of leaf scorch in Populus deltoids.