Characterization of Metabolites and Transcriptome of Pepper Accessions from Four Southern Provinces of China

Background/Objectives: Pepper (Capsicum annuum L.) is a widely grown vegetable and spice crop worldwide. This study aims to reveal the differences of metabolites among pepper accessions from different regions and explore candidate genes related to metabolites of pepper. Methods: The metabolome and transcriptome of 36 pepper accessions were determined by widely targeted metabolomics analysis and RNA sequencing technology, and the differential metabolites and differential genes among C. annuum from four important pepper production and consumption provinces of China, Hunan, Guizhou, Yunnan and Sichuan, were analyzed. Results: Flavonoids are the main characteristic metabolites that distinguish pepper accessions from Yun_Gui_Chuan Group and Hunan Group. The aglycones of characteristic flavonoids in each group are different; in Yun_Gui_Chuan Group mainly are luteolin, quercetin, chrysoeriol and isorhamnetin; in Hunan Group mainly are apigenin. Transcriptome data showed that two genes related to flavonoid 3′-monooxygenase differed significantly between the two groups of chili peppers, and we speculated that they may be the core enzymes regulating their flavonoid profile. And an SNP mutation located in gene Cgla06g001871 showed a strong correlation with pepper accessions from Yun_Gui_Chuan Group, which can be used as a DNA marker to identify pepper accessions from Yun_Gui_Chuan Group, and provide strong support for regional specialty variety conservation. In addition, we also analyzed the metabolites related to the taste and nutrition of pepper accessions in the four provinces, and the results showed that the sugar content of pepper accessions from Guizhou was low and the capsaicinoids content of pepper accessions from Sichuan was low, while no significant difference was found in acid and vitamin contents among pepper accessions from the four provinces. Conclusions: The metabolome and transcriptome of 36 pepper accessions from four important pepper production and consumption provinces of China were determined, and the characteristic metabolites and expressed genes of pepper accessions from each province were analyzed.