载果量对初果期晚熟杂柑风味及质地品质的影响

【目的】探讨不同树体载果量水平对初果期红桔、美国糖桔、春见、红美人和胡柚等5个晚熟杂柑品种风味品质及果实质地的影响，以期为各品种初果期最适宜树体载果量区间设定和鲜食品质提升提供理论依据。【方法】2019年，以生长势基本一致、4年生的各品种挂果树为材料，在设施栽培条件下设定单一载果量处理，以果实可溶性固形物（TSS）含量与可滴定酸（TA）含量比值变化趋势为主要指标，判断各品种果实成熟进程并选定相对适宜的采收期；2020年在此基础上设定高、低载果量2个处理，分别测定各品种成熟期果实TSS和TA含量，果肉和果皮中可溶性糖、有机酸组分及含量，以及果实质地相关参数，并对载果量与各果实品质指标进行相关分析。【结果】适宜的低载果量下，初果期红桔果肉中蔗糖、果糖、葡萄糖和柠檬酸含量不同程度提升；春见果肉中蔗糖、果糖和葡萄糖含量提升的同时柠檬酸含量下降、苹果酸含量提升；而红美人在低载果量下果肉中蔗糖含量下降、葡萄糖含量提升的同时苹果酸含量下降，各品种果肉中糖酸比例不同程度发生改变；至采收时，高载果量处理下红桔TSS/TA比值较低载果量降低12.7%；春见和美国糖桔2个品种TSS/TA比值较低载果量分别增加7.3%和7.1%。在红桔上，树体载果量水平与果皮硬度呈极显著相关（P<0.01，下同），与果皮韧性和果肉有机酸含量呈显著相关（P<0.05，下同）；在胡柚上，载果量与果皮韧性呈极显著相关，与果皮可溶性糖含量呈显著相关；在红美人上，载果量与果皮硬度呈显著相关，与果皮可溶性糖含量呈极显著相关；在春见上，载果量与果皮有机酸含量呈显著相关，与果肉可溶性糖含量呈极显著相关；在美国糖桔上，载果量与果肉硬度呈极显著相关，与果肉韧性呈显著相关；但所有供试品种果肉化渣性指标，即果肉紧实度和囊衣硬度与树体载果量水平均未表现出明显相关性。【结论】初果期红桔、红美人和胡柚3个供试品种在较低载果量下，TSS/TA比值略高、最终采收时综合风味更好，春见和美国糖桔2个品种则在较高载果量下TSS/TA比值略高，综合风味更佳。该结果可为不同品种柑橘控产提质技术的进一步完善提供数据支持和参考。

Effects of fruit load on the flavor quality and texture formation of medium and late maturing citrus cultivars in primary fruit period

【Objective】This study aims to explore the effects of different levels of tree fruit load treatments on the flavor quality and fruit texture of five late maturing citrus cultivars in their early bearing stage，including Red Tangerine（Citrus reticulata cv. Hongju）（RT），（C. clementine × C. sinensis）Osbeck var. Meiguotangju（MGTJ），（C. reticulata × C. sinensis）var. Okitsu No.44（Okitsu），（C. reticulata × C. sinensis）var. Ehime No. 28（Ehime） andC. grandis（L.）var. Huyou（Huyou），in order to provide a theoretical basis for identifying an optimal tree fruit load interval for each cultivar and the improvement of flavor quality during their primary fruit period.【Method】In 2019，four-year-old fruit-bearing trees were taken as materials. A single-level of tree fruit load treatment was set under the conditions of protected cultivation and the total soluble solid content/ titratable acidity content（TSS/TA）ratio change in fruits was used as the main indicator to judge the ripening process of each cultivar. In 2020，two different levels of tree fruit load treatments（low fruit load:I；high fruit load:II）were set to determine the relevant indicators of flavor quality during the near-maturity period of the fruit，including the TSS，TA，soluble sugar and organic acid contents in the flesh and peel，as well as the fruit texture indexes of the fully-ripened fruits. The correlation between fruit load and the fruit quality index were also analyzed. 【Result】The contents of sucrose，fructose，glucose and citric acid in the flesh of RT were increased to different degrees under the relatively lower fruit load treatment. In Okitsu，the contents of sucrose，fructose and glucose increased，while contents of citric acid decreased and malic acid increased. However，under low fruit loading，the content of glucose in Ehime decreased，glucose content was increased，malic acid content decreased. The ratio of sugar/acid in different cultivars changed at harvest time. In RT，the final TSS/TA ratio under high load treatment was 12.7% lower than that from the low load treatment. In contrast，the final TSS/TA ratio of Okitsu and MGTJ under the high load treatment were 7.3% and 7.1% higher than that of the low load treatment，respectively. In RT，tree fruit load level showed extremely significant positive correlation（P<0.01，the same below）with fruit skin hardness，as well as a significant positive correlation（P<0.05，the same below）with its fruit skin firmness and flesh organic acid content. In Huyou，tree fruit load level showed extremely significant and positive correlation with fruit skin toughness，as well as significant positive correlation with its peel soluble sugar content. In Ehime，the tree fruit load level showed a significant positive correlation with fruit skin hardness as well as extremely significant positive correlation with peel soluble sugar content. In Okitsu，the tree fruit load level showed a significant positive correlation with peel organic acid content as well as extremely significant positive correlation with flesh soluble sugar content. In MGTJ，the tree fruit load level showed extremely significant positive correlation with flesh hardness，as well as a significant positive correlation with its flesh toughness. However，among all the pulp indexes oftested varieties，there was no significant correlation between fruit firmness and tree fruit load levels.【Conclusion】 This study suggests that RT，Ehime and Huyou achieve a higher ratio of TSS/TA and better flavor under the relatively lower tree fruit load treatment whereas the ratio of TSS/TA and flavor quality of Okitsu and MGTJ are better under a relatively higher tree fruit load treatment in their early bearing stages. This study provides reference data to support the further improvement of production and quality control of citrus fruits.