Abstract: 【Objective】Loquat is native to China, has a long history of cultivation and medicinal use. Loquat phenolic substances, as natural antioxidants, have a variety of biological activities. At present, most studies on loquat phenolic substances and antioxidant activity only focus on single organ such as leaves, flowers, and fruits, and lack comparative analysis among the above mentioned organs. In addition, the evaluation of the antioxidant activity of loquat mainly involves ranking and evaluating the antioxidant activities measured by different methods, and there are few studies on comprehensive evaluation. In order to provide a theoretical basis for the breeding of new loquat varieties with high total phenolic, flavonoids content and high antioxidant activity, as well as to supply reference for the effectively developing and utilizing of loquat functional ingredients, this study explored the diversity of total phenolic, flavonoids contents and antioxidant activity in different organs of the loquat F1 hybrid population, and comprehensively evaluated the antioxidant activity.【Methods】The total phenolic, flavonoids content and antioxidant activity of different organs such as leaves, flowers and fruits were determined in loquat Ninghaibai and Oobusa, as well as in their twenty-nine F1 generations. The total phenolics content was determined by Folin-ciocalteu method, the flavonoids content was determined by sodium nitrite-aluminum chloride method. DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging capacity (DPPH value), ABTS (2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid) cation radical scavenging capacity (ABTS value), Ferric reducing antioxidant power (FRAP value) in vitro were determined by DPPH method, ABTS method and FRAP method, respectively. Diversity analysis and correlation analysis were conducted on the total phenolics, flavonoids and antioxidant activity of different organs of the hybrid offspring. In addition, a comprehensive evaluation and cluster analysis were conducted on the antioxidant activity of the hybrid progeny. 【Result】The results showed that there was a rich diversity in the total phenolics and flavonoids contents, as well as antioxidant activity in different organs of the loquat F1 generations of Ninghaibai and Oobusa. In their leaves, flowers and fruits, the coefficient of variation of total phenolics content was 23.84%, 9.51% and 16.50%, the coefficient of variation of flavonoid content was 49.48%, 13.38% and 44.67%, the coefficient of variation of DPPH value was 23.93%, 15.77% and 17.28%, the coefficient of variation of ABTS value was 26.98%, 13.93% and 21.82%, the coefficient of variation of FRAP value was 25.32%, 11.91% and 20.65%, the coefficient of variation of Antioxidant potency composite (APC) index was 23.85%, 10.43% and 17.42%, respectively. The coefficient of variation in different organs of hybrid offspring was leaves > fruits > flowers. Except for the total phenolic content of the flowers, the other traits were widely segregated and had high genetic potential. In addition, there are significant differences in the content of total phenolic, flavonoids content and high antioxidant activity in different organs of hybrid offspring, mainly in the order of flowers > leaves > fruits. The antioxidant activity of different organs was comprehensively evaluated using the APC index, the top three plants with high antioxidant activities in leaves were ND107, Oobusa and ND128. The top three plants with high antioxidant activities in flowers were ND164, ND165 and ND082, while the top three plants with high antioxidant activities of fruits were ND106, Oobusa and ND037. Correlation analysis showed that the total phenolics and flavonoids contents in leaves and fruits were significantly correlated with antioxidant activity, while the contents of total phenolics and flavonoids in flowers were correlated with antioxidant activity. Moreover, there was a significant positive correlation between APC index and in vitro antioxidant activities such as DPPH value, ABTS value and FRAP value, but there was no significant correlation between the total phenolics, flavonoids and antioxidant activity in different organs. Cluster analysis divided the 31 strains of hybrid offspring and their parents into 5 categories. The first and second groups contained 26 lines, which had moderate antioxidant activity. The third group only contained ND080, which had weak antioxidant activity in flowers and fruits. The fourth group only contained ND148, which had weak antioxidant activity in leaves but strong antioxidant activity in flowers and fruits. And the fifth group contained ND107, Oobusa and ND128, which had the strongest antioxidant activity in leaves.【Conclusion】The total phenolic and flavonoids contents and antioxidant activity of various organs were rich in diversity in the F1 generation of loquat Ninghaibai and Oobusa hybrids. Except for total phenolics in flowers, the total phenolics content, flavonoids content, DPPH value, ABTS value, FRAP value and APC index showed a wide range of trait separation and had good genetic potential. The genetic variation of leaf traits in F1 generation was more abundant than that in flowers and fruits. There were obvious differences in the total phenolics content, flavonoids content, DPPH value, ABTS value and FRAP value among different organs of the hybrid offspring, and the contents in flowers and leaves were much higher than that in fruits. Correlation analysis verified that total phenolics and flavonoids were important antioxidant components of loquat. There was no significant correlation between total phenols, flavonoids, antioxidant activity in different organs. APC index and cluster analysis could be used to screen the hybrid offspring with strong comprehensive antioxidant activity. The research results could provide a theoretical basis for the scientific configuration of hybrid combinations and improve the breeding efficiency, which could also supply a reference for the effectively developing and utilizing the functional components of loquat.
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