Comprehensive evaluation of the effects of different pollinizer varieties on fruit set and fruit quality of Jinsha pomelo based on principal component analysis

【Objective】Jinsha pomelo [Citrus maxima (Burm.) Merr.] is an excellent local variety in Jiangxi Province, China, and renowned for its exceptional sensory qualities. Based on our previous observations, self-pollinated Jinsha pomelo exhibited low fruit setting rate and poor fruit quality. Therefore, to ensure sustainable yields and commercial viability of Jinsha pomelo, it is necessary to either enhance natural cross-pollination sources or implement artificial pollination with heterologous pollen. The aim of this study was to investigate the effect of pollinations with different pollinizer varieties on fruit setting rate and fruit quality in Jinsha pomelo, and provide data support for selecting suitable pollen donors.【Methods】In this study, experimental trees were selected from Jinsha pomelo top-grafted on tenyears-old Poncirus trifoliata rootstocks, exhibiting vigorous growth with no signs of significant pests ordiseases. Prior to pollination, flower thinning was performed. In 2021, 4-5 full buds per inflorescence were retained for pollination; in 2023, 2- 3 full buds per inflorescence were retained. All pollinated branches were tagged according to their respective treatments. Inflorescences were isolated pre-anthesis using 28 cm × 17 cm parchment bags to prevent pollen contamination. For each pollination combination, 200-300 flowers were pollinated, with isolation bags removed 5 days post-pollination. Ten pomelo varieties- including Majia pomelo (GM), Hongroumiyou (FH), Sanhongmiyou (FS), Jinlan pomelo (JJ), Jinsha No.1 pomelo (JL), Taoximiyou (JT), Shatian pomelo (XS), Shangrao sour pomelo (GS) and Jingangshan sour pomelo (JS), Cocktail Grapefruit (NP) - were used as pollen donors for Jinsha pomelo in 2021 and 2023. Twelve fruit quality parameters - including the fruit setting rate, single fruit mass, peel thickness, peel CCI, edible rate, juice yield, juice vesicle number, titratable acid (TA), soluble sugar (SS), total soluble solids (TSS), vitamin C (Vc), and TSS:TA ratio - were evaluated through variation range screening by principal component analysis (PCA) for comprehensive assessment.【Results】In vitro pollen germination tests across both experimental years confirmed that the germination rate of all the pollen donors exhibited ＞50% validating their viability for successful pollination and fertilization. In 2021, the pollens of Jinggangshan sour pomelo showed the highest germination rate was detected in Jinggang sour pomelo pollen with (83.15%), while the pollens of Taoximiyou pomelo ranked highest in 2023 (74.64% ). Furthermore, the twelve fruit quality parameters exhibited significant variation across pollination combinations, with variation ranges from 12.92% to 3 487.10%. Among them, the variation of the fruit setting rate among different pollination combinations ranged from 15.45% to 42.36%; the variation of the single fruit mass among different pollination combinations ranged from 20.52% to 38.70% ; the variation of the peel thickness among different pollination combinations ranged from 14.74% to 32.73%; the variation of the peel CCI value among different pollination combinations ranged from 39.64% to 3 487.10%; the variation of the edible rate ranged from 18.21% to 50.94%; the variation of the juice rate ranged from 30.38% to 50.44% ; the variation of the number of juice vesicles ranged from 13.56% to 26.09% ; the variation of the titratable acid content ranged from 29.84% to 49.91%; the variation of the soluble solids content ranged from 7.33% to 20.26%; the variation of the soluble sugar content ranged from 14.82% to 31.37% . the variation of the vitamin C content ranged from 19.55% to 25.02%, and the variation of the solid-acid ratio ranged from 34.50% to 50.66%. The cross-pollination results revealed strong pollen-parent dependency in both fruit setting rate and quality parameters. The above quality indicators were further analyzed by principal component analysis (PCA), and the cumulative contribution rates were all above 93.00% in 2021 and 2023. The PCA of replicated two-year trials demonstrated that the key traits governing post-pollination fruit quality in Jinsha pomelo included: the single fruit mass, fruit setting rate, peel CCI, titratable acid (TA), soluble sugar (SS), and total soluble solids (TSS), especially TSS, TA, and TSS:TA ratio. The results of the PCA showed that Majia pomelo (GM), Hongroumiyou (FH) and Shatian pomelo (XS) were regarded as top-performing pollen donors.【Conclusion】In this study, we evaluated the pollinaiton effects of the ten pollen donors (GM, NP, GS, JS, FH, FS, JT, JL, JJ, and XS) on Jinsha pomelo and demonstrated that cross-pollination significantly enhanced the fruit setting rate and quality traits of Jinsha pomelo fruits. The twelve fruit quality parameters were subsequently extracted for principal component analysis (PCA). The scores and rankings of the principal component composite factors ranked Majia pomelo as the optimal pollinizer for Jinsha pomelo, followed by Hongroumiyou pomelo and Shatian pomelo. The results in this study demonstrated that using proper pollinizer would significantly enhanced Jinsha pomelo's comprehensive fruit quality, providing both mechanistic insights and practical guidance for optimizing orchard pollina-tion strategies through pollen donor selection.