The influence of exogenous gibberellin (GA3) on fruit quality of different peach varieties(strains)

Abstract：【Objective】Exogenous GA₃ is widely used to regulate fruit growth and development, which is closely related to fruit quality. The sensitivity of exogenous GA₃ varies among different fruit tree species. The aim of this study was to investigate the effects of different concentrations of exogenous GA₃ on single fruit quality, fruit shape index, colour difference, hardness, soluble solid content (SSC), soluble sugar content, organic acid content, sugar-acid ratio of fruits of different peach varieties (strains), in order to provide a theoretical basis for the improvement of the comprehensive quality of fruits of different peach varieties (strains).【Methods】Peach trees of DB2-9, Xiahui 8 and Xiacui were used as experimental materials. The experiment included 4 treatments: T1 (spraying equal amount of water), T2 (50 mg·L^-1 GA₃), T3 (100 mg·L^-1 GA₃), and T4 (150 mg·L^-1 GA₃), and each treatment included three trees that were sprayed four times, every 10 d, starting from 48, 50, and 46 d after full bloom, respectively. Twenty fruits were randomly collected from each treatment (three replications) at the hard core stage, expansion stage and ripening stage for the determination of external and internal quality indexes of fruits. All data were statistically analyzed. 【Results】In this study, the quality of single fruit of T2 of Xiahui 8 and Xiacui was significantly higher than other treatments during the expansion and ripening stages; during the ripening period, the quality of single fruit under T2 and T3 of DB2-9 was significantly higher than T1 and T4. During the expansion period, the shape index of T1 of DB2-9 and Xiacui was significantly lower than other treatments; and during the three periods, the shape index of T2 of Xiahui 8 was significantly lower than other treatments. The soluble solid content of T1 of Xiacui was higher than other treatments at the hard core and expansion stages, while the soluble solid content of T1 of DB2-9 and Xiahui 8 was significantly lower than other treatments at the expansion and ripening stages. During the ripening period, there was no significant difference in the hardness with peel and hardness without peel among the treatments of DB2-9; during the expansion period, the hardness with peel and hardness without peel of T4 of Xiahui 8 was higher than T1; during the three periods, the hardness with peel of T3 of Xiacui was significantly higher than T1. During the expansion period, the L^* value of T3 and T4 of DB2-9 and Xiacui was significantly lower than T1; during the expansion and ripening periods, the L^* value of T2 of Xiahui 8 was significantly higher than T1. In the entire period, the a^* value of T4 of DB2-9 was significantly higher than T1 and T2; at the maturity stage, the difference in the a^* value between treatments of Xiahui 8 was not significant, and the a^* value under T1 of Xiacui was significantly higher than other treatments. At the ripening stage, the C value of T3 and T4 of DB2-9 and Xiacui was significantly lower than T1, while the differences among treatments were not significant in Xiahui 8. At the ripening stage, the a/b value under T3 and T4 of DB2-9 and Xiahui 8 was significantly higher than T1 and T2, while the differences among treatments were not significant in Xiacui. The soluble sugar content under T1 of DB2-9 was significantly lower than other treatments during the expansion and ripening periods; the sucrose content, sorbitol content and total sugar content under T2 of Xiahui 8 were significantly lower than T1 during the hard core stage, while they were significantly higher than T1 during the ripening period; the soluble sugar content under T2 and T3 of Xiacui was lower than T1 during the expansion period, while at the ripening stage, there was no significant difference in the glucose content, fructose content and total sugar content among the treatments of Xiacui. At the ripening stage, the quinic acid content and total acid content under T1 of DB2-9 were significantly lower than other treatments; at the hard core stage, the organic acid content under T1 of Xiahui 8 was significantly lower than other treatments, whereas the quinic acid content, malic acid content and total acid content under T4 of Xiahui 8 were significantly higher than T1 at both the expansion and ripening stages; and at the ripening stage, the quinic acid content, malic acid content and total acid content of T3 and T4 of Xiacui were higher than T1. In the expansion and ripening periods, the sugar-acid ratio under T3 of DB2-9 was significantly higher than T1; in the ripening period, there was no significant difference in the sugar-acid ratio among the treatments of Xiahui 8; and the sugar-acid ratio under T2 and T3 of Xiacui was significantly lower than of T1 and T4 in the three periods.【Conclusion】The application of 100 mg·L^-1 GA₃ significantly increased the quality of single fruit, SSC, total sugar content and sugar-acid ratio of DB2-9 at the ripening stage, while it had no significant effect on the colouring of fruits; the exogenous application of 50 mg·L^-1 GA₃ increased the single fruit quality and SSC of Xiahui 8 at three periods, as well as the total sugar content and sugar-acid ratio at maturity, and significantly increased the L^* value of fruits at maturity; and the exogenous application of 50 mg·L^-1 GA₃ increased the quality of single fruit and hardness with peel of Xiacui in the three periods, as well as the SSC and total sugar content in the ripening stage of fruits. Overall, the exogenous application of 100 mg·L^-1 GA₃ can improve the overall quality of fruits of DB2-9; the exogenous application of 50 mg·L^-1 GA₃ can improve the overall quality of fruits of Xiahui 8 and Xiacui.

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