Effects of different training systems on the fruit quality in Yuluxiang pear

【Objective】Yuluxiang pear (Pyrus bretschneideri Rehder) is a hybrid pear variety with Kuerlexiangli pear as the maternal parent and Xuehuali as the paternal parent. It has the characteristics of high yield, excellent fruit quality, and good storage resistance. In recent years, it has gradually become the leading variety in the layout of the modern pear fruit industry and the renewal of pear varieties. The objective of the experiment is to explore the effects of different training systems on the amino acid content and fruit quality of Yuluxiang pear, so as to provide a reference basis for the suitable cultivation mode of Yuluxiang pear.【Methods】Fifteen years old Yuluxiang pear trees were used as the test materials, and five training systems, including slender spindle system, open-center system, free spindle system, Double Arm Along- the- Row Trellis system (DAART) and delayed- open central leader system, were selected for the study. The contents of free amino acids in the fruit were detected by using an AB SCIEX 5500 QTRAP liquid chromatography mass spectrometry (LC-MS) instrument, and external and internal quality of the fruits were measured. The external quality included the single fruit weight, longitudinal diameter, transverse diameter, fruit shape index, and fruit color. The internal quality included the soluble solids content (SSC), firmness, total soluble sugar content, and organic acid content. Moreover,statistical analyses were conducted to examine differences and correlations in free amino acid content, external quality, and internal quality of the fruits.【Results】The results showed that different training systems had no influence on the types of amino acids in Yuluxiang pear, based on a total of 16 kinds of free amino acids detected. Among them, serine (Ser) had the highest content, followed by aspartic acid (Asp), and histidine (His) had the lowest content. The total contents of free amino acids and essential amino acids in the fruit with DAART system were the highest, while those with the free spindle system were the lowest. This study systematically evaluated the effects of different training systems on fruit quality characteristics. DAART system consistently demonstrated superior performance in multiple quality parameters compared to other training systems. The fruits with DAART system showed the maximum single fruit weight, the greatest longitudinal diameter, and the optimal fruit shape index, along with better fruit coloration. The highest SSC (13.57%) was observed in DAART system, showing significant differences (P＜0.05) compared to the slender spindle system, free spindle system, and delayedopen central leader system. DPLAR system produced fruits with the highest total sugar content (131.55%), which was significantly different (P＜0.05) from that of the delayed-open central leader system and free spindle system. The lowest total acid content (2.62 g·L-1 ) was recorded in DAART system, with significant differences (P＜0.05) compared to the slender spindle system and open-center system. A comprehensive correlation analysis revealed significant relationships between specific amino acids and quality attributes in fruits. Isoleucine (Ile) had a significant negative correlation with longitudinal diameter, fruit color a value and b value. Leucine (Leu) and lysine (Lys) had a significant positive correlation with soluble solids content, fruit firmness and and total acid content, and a significant negative correlation with fruit color L value and total sugar content. Valine (Val) had a significant negative correlation with fruit color a value and b value. Threonine (Thr) had a significant negative correlation with fruit color a value. Phenylalanine (Phe) had an extremely significant negative correlations with longitudinal diameter, fruit shape index, fruit color a value and b value. Methionine (Met) had a significant negative correlation with total sugar content. Threonine (Thr) had a significant negative correlations with fruit color a value. These findings demonstrate complex metabolic relationships between essential amino acids and fruit quality parameters, suggesting potential biochemical pathways influencing pear fruit development and maturation. These morphological advantages suggest that DAART system promotes more favorable fruit development conditions compared to alternative training systems. The observed improvements in both size parameters and color attributes are particularly significant for commercial fruit production, as they directly influence marketability and consumer preference.【Conclusion】DAART training system demonstrated significant advantages for Yuluxiang pear production. The total amino acid content and fruit quality with DPLAR system were better, which is more conducive to the growth of Yuluxiang pear.