Integrated transcriptomic and metabolomic analyses of ‘Guifei’ mango fruit flavor in an endospermic genotype and a mutated genotype without endosperm

Targeted transcriptomic and metabonomic analyses were conducted to explore the metabolic basis of amino acids, organic acids, terpenoids, esters and carotenoids in two genotypes of mango cultivars 'Guifei,' an endospermic genotype and a mutant genotype without an endosperm that produce large- and small-sized fruit, respectively, with different flavor metabolite contents. A total of 88 different metabolites were separately identified in the pulp of different-sized mango fruit, including organic acids, amino acids, phenolic acids and saccharides. Seventy-three types of volatile organic compounds (VOCs) were identified in the pulp of different-sized mango fruit based on metabolomics. The major volatile compounds identified were terpenoids, esters and aromatics. p-Mentha-1(7),2‑dien-8-ol, Selina-6-en-4-ol and 1,3-Dimethyl-5-(propen-1-yl) adamantane are major terpenes that play an important role in the aroma of 'Guifei' mango fruits. In addition, p-Mentha-1(7), 2‑dien-8-ol was found in the mutant genotype without endosperm for the first time and had a relatively high concentration in the glycosidically bound form in 'Guifei' mango. Twelve types of carotenes were identified in the pulp of different-sized mango fruits. The carotenoid contents of the two genotypes were significantly different, and β-cryptoxanthin and zeaxanthin were the key metabolites that caused the difference in the total carotenoid content between the examined cultivars. The integrated analysis of carotenoid metabolism data and transcriptome data showed that GGPS, Z-ISO and NCED were the key genes that led to the differences in fruit flavor and carotenoid content of the mango pulp. This study provides new insights into the effects of mutant genotypes on the appearance and intrinsic quality of fruit.