Changes in sugar and acid components contents and comprehensive quality evaluation during fruit development of Orah with different rootstocks

【Objective】This study aimed to investigate the changes in sugar and acid components during the fruit development of Orah grafted onto different rootstocks and to comprehensively evaluate the fruit quality to determine the optimal harvest time for each rootstock. The findings would provide theoretical basis for the scientific cultivation and management of Orah.【Method】Orah with Poncirus trifoliate Raf，Citrus junos Sieb. ex Tanaka and C. reticulata Blanco as rootstocks were selected as research subjects to investigate the dynamic changes in sugar，acid，and other fruit components from July 2022 to April 2023，and the fruit quality was comprehensively evaluated using principal component analysis. 【Result】The sugar and acid components contents of Orah varied among different rootstocks during fruit development， though the overall trends were consistent. As the fruit developed and matured，contents of soluble solids，sucrose，glucose，fructose，total soluble sugars，as well as sweetness value，sweetness-to-acid ratio and solid-to-acid ratio increased， while contents of maltose，titratable acid，citric acid and total organic acids decreased. Malic acid content initially decreased and then increased，while vitamin C（Vc）and shikimic acid contents first increased and then decreased. Benzoic acid and tartaric acid contents remained relatively stable，while succinic acid content fluctuated. Correlations were observed among various quality indicators. Each two of soluble solids，fructose，glucose，sucrose，total soluble sugars， sweetness value，sweetness-to-acid ratio and solid-to-acid ratio were all extremely significantly positively correlated （P<0.01，the same below），each two of titratable acid，citric acid and total organic acids were extremely significantly positively correlated. Orah with P. trifoliate Raf and C. junos Sieb. ex Tanaka as rootstocks had the best overall quality in April，while Orah with C. reticulata Blanco as rootstock had the best overall quality in March. Among the 3 rootstocks， from November to December，Orah with P. trifoliate Raf as rootstock had the highest comprehensive score；in January， Orah with C. junos Sieb. ex Tanaka as rootstock had the highest comprehensive score；in February，Orah with Citrus reticulata Blanco as rootstock had the highest comprehensive score；and from March to April，Orah with P. trifoliate Raf and C. reticulata Blanco as rootstocks had higher comprehensive score than Orah with C. junos Sieb. ex Tanaka as rootstock.【Conclusion】The overall quality of Orah grafted onto all 3 rootstocks is higher in March and April compared to January and February. In Guangxi，Orah grafted onto P. trifoliate Raf is preferable for harvest in December，Orah grafted onto C. junos Sieb. ex Tanaka or C. reticulata Blanco is preferable for harvest in January or February，and Orah grafted onto P. trifoliate Raf or C. reticulata Blanco is preferable for harvest in March or April.