Comprehensive analysis on the fruit quality of Yuluxiang pear in different production areas

Abstract：【Objective】In order to determine the suitability of geological locations and climatic conditions for production of Yuluxiang pear (Pyrus bretschneideri Rehder‘Yuluxiang’) with excellent fruit quality, we measured the fruit quality components such as fruit color, contents of anthocyanin and chlorophyll, firmness, soluble solid content (SSC), total soluble sugar content (TSSC) and titratable acid content (TAC) of Yuluxiang fruit from five locations with different geographical and climatic conditions in northern China.【Methods】The five locations for Yuluxiang pear production included Xi County, Fenxi County and Ruicheng County in Shanxi Province, Haidian District in Beijing and the 33rd Agricultural Production Regiment in Xinjiang were selected as experimental sites. A representative orchard in each of these sites was then selected for the experiment from 2020 to 2022. Climatic and geographical conditions including average altitude, average annual temperature, average diurnal temperature difference during the fruit color development, average annual sunshine duration and frost-free period were investigated in each of these orchards. The experimental Yuluxiang pear trees in each of these orchards were 8 to 10 years old and the tree canopy was in the free- spindle shape. All the orchards were with loam soil and manual fertilizer applied annually in the fall, and managed under the common production practice. There were 3 trees in the experimental unit in each orchard. Four representative fruit at harvest maturity were collected at a height of 1.0-2.5 m in the outer canopy from each of the trees to measurethe fruit quality components. The experiment was replicated 3 times in each orchard. Fruit color was measured using the photoshop CS6 to read the Lab color degree (L*, a*, b*) on the fruit photograph and the h°= arccot (a*/b*)×180/π was used for the hue. Anthocyanin in the fruit peel was extracted using the HCl method and chlorophylls were extracted in 80% acetone. Ratio of the anthocyanin content to chlorophyll content was then determined. Fruit firmness in the flesh was determined using a FT327 pressure tester and the soluble solid content was measured with a PAL-1 reflectormeter. Total soluble sugar content and titratable acid content were determined using the anthrone colorimetry and the acidbase titration methods, respectively. Ratio of the sugar to acid was then calculated. Statistical software DPS7.05 was used for ANOVA, regression, cluster, and principal component analyses of the resulting data.【Results】Compared to those from Ruicheng County and Haidian District orchards, pear fruits from Xi County, Fenxi County and the 33rd Agricultural Production Regiment orchards looked more shiny with greater redness and yellowness in the surface, and in addition, the fruit anthocyanin contents were over 2-fold higher and the chlorophyll contents were 12%-21% lower. The fruit firmness from the 33rd Agricultural Production Regiment was the highest among those from all the five experimental orchards. The soluble solid content of fruit from the five experimental orchards were in the following order: the 33rd Agricultural Production Regiment (14.4%)＞Fenxi County (12.2%)＞Xi County (12.1%)＞ Ruicheng County (10.9%)＞Haidian District (10.6%). Total soluble sugar content of fruit from the 5 experimental orchards was in the order of the 33rd Agricultural Production Regiment (12.2 g · 100 g-1 )＞ Xi County (10.4 g·100 g-1 )＞Fenxi County (10.3 g·100 g-1 )＞Ruicheng County (9.1 g·100 g-1 )＞Haidian District (8.6 g·100 g-1 ). Fruit titratable acid content from the Xi County and Fenxi County orchards were 7%-10% greater than those from the rest of the orchards. The fruit redness was positively correlated with the altitude of the orchard-site, average diurnal temperature difference during the fruit color development, and average annual temperature. Fruit SSC or TSSC were positively correlated with the average diurnal temperature difference during the fruit- color development and average annual sunshine duration. Cluster analysis revealed that fruits from Xi County and Fenxi County orchards were in the same cluster with greater level of SSC, TSSC and TAC, and reduced firmness. Fruits from the 33rd Agricultural Production Regiment orchards were also in the same cluster but with less TAC. Fruits from orchards in Ruicheng County and Haidian District were in the same cluster with lower level of SSC and TSSC.【Conclusion】When the average altitude of the production orchard was in the range of 900-1100 m, and the average diurnal temperature difference was from 13 to 15 ℃, the excellent fruit quality of Yuluxiang pear was fully reached, whereas in the orchards with an average altitude below 400 m above sea-level, it was not suitable for production of this pear cultivar. Therefore, geographical and climatic conditions determined the suitability of the production of high- quality Yuluxiang pear.