Quality and Genetic Characterization of ‘Jinfengzao’, an Early‐Ripening Bud Mutant of ‘Newhall’ Navel Orange ( Citrus sinensis L.)

ABSTRACT Citrus fruits are nutrient‐rich, and most varieties originate from bud mutations. This study examined the quality characteristics of ‘Jinfengzao’, an early‐ripening bud mutant (MT) of the wild type (WT) ‘Newhall’ navel orange, by comparing the morphology, fruit quality and sucrose‐ and citric‐metabolic gene expression between the two cultivars. The results revealed significant differences in DNA levels and agronomic morphology between MT and WT. MT fruits had higher fruit weight, redder peel colour and greater carotenoid and sugar contents but lower chlorophyll and organic acid levels than WT fruits. Gene expression analysis demonstrated that CsSPS1 expression in MT was significantly higher than that in WT, positively correlated with sucrose content. Additionally, CsACO1 , CsNAD‐IDH3 and CsACL1 expression levels in MT were significantly higher than those in WT, displaying significant negative correlations with citric acid content. These findings suggested that MT exhibited genetic and morphological differences from WT, with superior fruit quality attributed to the increased expression of CsSPS1 , CsACO1 , CsNAD‐IDH3 and CsACL1 , which influenced the accumulation of soluble sugars and organic acids.