Abstract:

‘Fuji’apple trees were de-fruited at 31 days after full bloom. The bud growth，flowering rate，and endogenous sugar levels in terminal spur buds and bud-adjacent leaves were surveyed. Additionally，genes associated with sugar metabolism（e.g.，MdSPS6，MdSUSY1，MdHXK1 and MdSUT1） and flowering（e.g.，MdFT，MdFD，MdCO，MdSOC1，MdLFY and MdAP1）as well as three MdTPS genes in apple terminal spur buds were studied by quantitative real-time PCR. The results revealed that  de-fruit treatment improved the flowering rate and increased bud size and fresh weight. The content of sucrose，fructose and sorbitol in terminal spur buds had obvious changes，which were significantly higher than in the control during late stage of flower buds physiological differentiation，while the glucose content changed little. In spur leaves，de-fruit treatment advanced the first peak of 4 soluble sugars from 60 to 40 days after full bloom. Genes associated with sugar metabolism and 3 MdTPS in terminal buds all responded to de-fruit treatment. Furthermore，the expression of MdFT，MdFD，MdCO，MdSOC1，MdLFY were significantly up-regulated at 40 days after full bloom. The change of MdLFY was the most obvious，while MdAP1 had no significant difference compared with the control in the whole physiological differentiation period.

Key words: apple, de-fruit, flowering, soluble sugar, gene expression