Abstract:

‘Fengwan’orange（Citrus sinensis L. Osbeck）is the spontaneous late-ripening mutant of ‘Fengjie 72-1’. The expression of citrate metabolic related genes during fruit four developmental stages of Fengwan and its wild type Fengjie 72-1 orange was analyzed by qRT-PCR and the results revealed that key genes of glycolysis metabolism in Fengjie 72-1 expressed higher than that in Fengwan. However，citrate biosynthesis genes，such as CsCS4，CsPEPC1，CsPEPC2，CsPEPC4，CsME1 and CsME4 expressed lower than that in Fengwan. Moreover，transcript levels of genes，such as CsACO1，CsGAD4 and CsGS1 involved in citrate degradation pathways were increased gradually during fruit late development，and the expression levels in Fengjie 72-1 were higer than that in Fengwan orange. Genes involved in synthesis and degradation metabolic pathways coordinately contribute to the different content of citric acid. Correlation analysis revealed that CsME1 and CsME4 may be key genes affecting the different content of citric acid between Fengwan orange and its wild type.

Key words: navel orange, late-ripening bud mutant, citric acid, quantitative real-time PCR, glycolysis metabolism, TCA cycle