Analysis and evaluation of difference in fruit quality of wild red raspberries in Hebei province

Abstract: 【Objective】The study investigated the differences in the fruit quality of wild red raspberries (Rubus idaeus L.) in order to provide reference for efficient cultivation and variety breeding of red raspberry.【Methods】Wild red raspberries in Hebei Province was used as the research object, and a comparative analysis of the differences in the fruit characteristics of wild red raspberries from different regions was performed involving the determinations of external phenotypic traits, internal nutrient composition and other indexes of the fruit, and correlation analysis, principal component analysis and cluster analysis were applied to comprehensively evaluate the fruit quality of wild red raspberries.【Results】Longitudinal and transverse diameters of the fruits in each area ranged from 9.64 to 14.41 mm and 9.48 to 16.30 mm, respectively, with the largest fruit size occurring in Xinglong and the smallest in Changli and Fuping. Comprehensive comparisons revealed that the fruit size of wild red raspberries in northern Hebei was significantly greater than that in eastern Hebei, the West Hebei Taihang Mountains and northwestern Hebei, with longitudinal and transverse diameters ranging from 11.68 to 16.30 mm. There was no significant difference in fruit shape among areas. There were obvious regional differences in fruit yield, and single fruit weight and yield per plant in each area ranged from 0.34 to 2.03 g and 23.89 to306.70 g, respectively, with those in Xinglong area being significantly higher than those of the other areas, and Changli and Fuping being the lowest. A comprehensive comparison found that the single fruit weight and yield per plant in Northern Hebei were significantly higher than those of the other regions. In fruit nutrient composition, the soluble protein and amino acid contents in wild red raspberry fruits in each area were between 1.10 to 1.97 mg·g-1 and 9.84 to 12.96 mg·g-1 , respectively, and the soluble protein content of Funing red raspberry and the amino acid content of Chicheng red raspberry were significantly higher than those in the other areas. The vitamin C and anthocyanin contents varied greatly among areas, ranging from 8.40 to 29.79 mg · 100 g-1 and 203.02 to 599.19 mg · kg-1 , respectively, with vitamin C content of red raspberries in Chicheng, and flavonoid content in Kuancheng area being significantly higher than those in the other areas. There was no regional distribution pattern of flavonoids and total phenols in wild red raspberry fruits, which ranged from 2.32 to 6.69 mg·g-1 and 1.91 to 4.24 mg·g-1 , respectively, and the total phenol content of red raspberries in Luanping, and the anthocyanins content of red raspberries in Funing and Changli were significantly higher than those in the other areas. Comprehensive comparisons revealed that the soluble protein content of red raspberries from West Hebei Taihang Mountains was higher than that of other regions, ranging from 1.78 to 1.84 mg·g-1 ; the red raspberries from Northwestern Hebei had a high vitamin C content of 22.83 to 29.79 mg·100 g^{- 1} and a high amino acid content of 12.47 to 12.96 mg·g^{- 1} . The anthocyanin content of red raspberries from Eastern Hebei was relatively high, ranging from 587.82 to 599.19 mg·kg^-1 . Soluble sugar and titratable acid contents differed significantly, ranging from 51.24 to 84.69 mg·g^-1  and 45.53 to 75.27 mg·g^-1 , respectively; the soluble sugar content of red raspberries in Kuancheng, and the titratable acid of red raspberries in Funing and Yixian were significantly higher than those in the other areas. The acid-sugar ratio ranged from 0.72 to 1.48, with the highest in Xinglong and the lowest in Changli. The soluble solid content and solid-acid ratios ranged from 9.53% to 14.77% and 1.45 to 2.67, respectively, and the two indexes in Xiahuayuan were significantly higher than those in the other areas. Comprehensive comparison revealed that Kuancheng, Xinglong and Weichang in the northwestern Hebei and northern Hebei regions had a higher soluble sugar content, solid-acid ratio and sugar-acid ratio, together with a lower amount of titratable acid, resulting in a sweeter fruit flavor and a richer texture; however, Changli and Funing in East Hebei and Yixian, Lai and Fuping in the West Hebei Taihang Mountains had a lower soluble sugar content and greater amount of titratable acid, which resulted in a more acidic fruit flavor. Correlation analysis of 18 indicators, including fruit traits, yield, nutrient composition and flavor, revealed a total of 19 pairs of correlated indicators. Accordingly, through principal component analysis, the 18 indicators were simplified into 4 relatively independent composite indicators, with a cumulative variance contribution rate of 88.530%, and the top three areas in terms of fruit quality composite score were Kuancheng, Xinglong and Weichang. A cluster analysis revealed that wild red raspberries in northern Hebei Province had outstanding fruit quality compared with those in the other regions; the wild red raspberries in the 13 sampling sites were divided into three categories: the first category included Weichang and Longhua, and the second Funning, Yixian, Laishui, Chicheng, Xiahuayuan, Fuping, and Changli.; and the third Luanping, Chengde, Kancheng and Xinglong.【Conclusion】A comprehensive evaluation of fruit quality revealed that the wild red raspberries in northern Hebei Province have large yields and good flavors and are suitable for table fruit production, whereas those in northwestern Hebei Province, the West Hebei Taihang Mountains and eastern Hebei Province, which have outstanding fruit organic content, are suitable for the production of wild red raspberries for processing and other purposes.