Xenia effect of 'Murcott' tangor pollen on sugar-acid metabolism and phenolic compounds in Fuju.

The sweetness of citrus fruits is primarily determined by the concentrations and ratios of sugars and organic acids. The xenia effect, defined as the influence of pollen genotype on fruit phenotype, has been reported in several fruit crops and may affect traits such as fruit shape, sugar-acid balance, ripening time, and seed characteristics. This study aimed to evaluate the effects of Murcott tangor (Citrus reticulata × Citrus sinensis) pollen on sugar-acid metabolism and phenolic composition in Fuju fruit (Citrus reticulata 'Tangerina') through controlled cross-pollination. Self-pollinated Fuju fruits were used as controls. Changes in sugars, organic acids, phenolic compounds, and related metabolic gene expression patterns during fruit development were analyzed using metabolite profiling, and quantitative gene expression analysis. The results indicated that Murcott pollen-pollinated Fuju fruits exhibited altered sugar accumulation patterns during the late developmental stage (210-230 days after flowering), with sucrose content increasing by approximately 15% compared with self-pollinated Fuju at harvest. These changes were associated with altered expression patterns of sucrose metabolism-related genes, including sucrose synthase and neutral invertase. Citric acid content showed no significant differences among pollination treatments, suggesting that xenia-associated effects were more evident in sugar accumulation than organic acid accumulation under the conditions tested. These findings indicate that Murcott tangor pollen is associated with changes in sugar accumulation patterns and phenolic profiles in Fuju fruit, providing insights into the potential contribution of pollen genotype to citrus fruit quality development.