Pre-harvest application of forchlorfenuron enhances fruit quality and bioactive substance accumulation in Chunhua loquat.

Chunhua loquat is a novel cultivar that effectively avoids frost damage. However, the quality characteristics of loquats are limited, and the effects of forchlorfenuron application on loquat fruit quality and bioactive substance accumulation remain unclear. In this study, forchlorfenuron was applied at concentrations of 0 (control), 10, 20, 30, and 40 mg/L to the fruit at 24 and 38 days after bloom. Results showed that forchlorfenuron increased fruit weight by at least 9.32 % and improved the sugar-to-acid ratio by at least 25.26 %. Additionally, forchlorfenuron increased the levels of the most detected aroma compounds, such as terpenoids, ketones, and alcohols. Specifically, 2-hexenal (E)- and 2-hexenal, the most abundant compounds, increased by 17.58 % at 20 mg/L. Forchlorfenuron altered phenylpropane metabolism, upregulating C4H, COMT, CCR, and HCT expression, which affected the content of bioactive substances such as total phenolics, flavonoids, p-hydroxybenzoic acid, and cinnamic acid. Forchlorfenuron also modulated carotenoid metabolism by upregulating CCD, CYCB, BCH, and NCED expression, which affected the content of β-cryptoxanthin, β-carotene, and α-carotene. Furthermore, forchlorfenuron modulated endogenous hormone levels, thereby affecting the accumulation of bioactive substances. In conclusion, forchlorfenuron enhances fruit quality and bioactive substance accumulation in loquat, with an optimal effect at 20 mg/L.