Integrated metabolomic profiling and transcriptome analysis of fruit quality and ripeness in early-maturing seedless triploid loquat

The triploid loquat is a precious germplasm resource with a characteristic large fruit having no seeds and a stronger growth vigor. However, the flavor composition and regulation mechanism of loquats with different ploidy levels remain unclear. Here, we investigated the mechanism of loquat flavor formation on 'Changbai No.1'(diploid), 'Wuhe Zaoyu' and 'Huayu Wuhe No.1'(triploid) by combining ultra-performance liquid chromatography tandem mass spectrometry with transcriptome analysis. A total of 1163 metabolites were detected, less than 300 of which were differentially accumulated, including phenolic acids, flavonoids, amino acids, organic acids, and saccharides. Moreover, our results indicate that triploid loquat possesses health benefits due to its unique bioactive chemicals and medicinal value. The specific presence of ethyl isobutyrate explains the improved flavor of the triploid loquat. By analyzing the carbohydrate metabolism pathway and correlated differentially expressed genes, 20 candidate genes related to Brix, eight candidate genes related to L-ascorbic acid, and four candidate genes related to pectin in early-maturing triploid loquat fruit were identified. This study broadens the knowledge of ripening-related metabolism in loquats and provides new insights into the flavor mechanism and high-quality breeding of loquat fruit.