Quality analysis and comprehensive evaluation of 24 jujube seed kernels in northern Shaanxi

Abstract:【Objective】Sour jujube is a wild type of cultivated sour jujube with a long history and has attracted much attention due to its high value of traditional Chinese medicine. As one of the main production areas of sour jujube, northern Shaanxi has rich sour jujube germplasm resources. The quality of sour jujube is not only related to genetic background, but also affected by the place of origin and environment, showing different characteristics of the place of origin. There are geographical differences in the quality of sour jujube fruit, the appearance of the core and the functional components of sour jujube kernel. The evaluation and screening of sour jujube genetic resources in northern Shaanxi have positive significance for promoting the sustainable development of the sour jujube industry. The study aimed to comprehensively analyze the quality of sour jujube kernels from different production areas in northern Shaanxi, so as to accurately screen out sour jujube genetic resources of different quality types, thereby providing a scientific basis for the development and utilization of sour jujube genetic resources.【Methods】In the study, 24 types of wild sour jujube kernels were selected from seven production areas along the Yellow River in northern Shaanxi as the research objects. The apparent traits and functional components of wild sour jujube kernels were comprehensively evaluated by using diversity analysis methods, such as coefficient of variation analysis, correlation analysis and cluster analysis, combined with comprehensive evaluation methods, like probability classification and principal component analysis.【Results】Analysis of the phenotypic characteristics of Ziziphus jujuba var. spinosa kernels from different provenances showed that the wild jujube kernels from Hebei had the largest weight and were significantly higher than those from other provenances, and the kernels from Shandong provenance had thelargest longitudinal diameter (7.30 mm) and transverse diameter (5.36 mm). The longitudinal diameter (5.24 mm) and transverse diameter (4.44 mm) of seed kernels in Jiaxian county were the smallest. The benevolence index was as follows: Shandong＞Ganquan＞Qingjian＞Yanchuan＞Wubu＞Suide＞Yanchang＞Jiaxian. The sour jujube kernels in Shandong were mostly oval in shape, while the sour jujube kernels in northern Shaanxi were nearly round. Among the 24 samples, Shandong had the highest edible rate of 79.51%, which was significantly higher than that from other provenances. Yanchang ranked second with 76.26%, and Jiaxian county had the lowest edible rate (59.02%). The main metabolites in sour jujube kernels, including fatty acids, total flavonoids and total saponins, were determined and analyzed. The results showed that the fatty acid content of sour jujube kernels in Wubu was the highest at 24.54%, while the content in Suide was only 20.03%. All samples were clustered based on 17 sour jujube appearance traits and 3 main quality component content indicators. The 8 production areas were divided into 3 categories. The first category included Ganquan, Yanchang, Qingjian and Jiaxian. The second category included arid Yanchuan, Wubu and Suide. The third category only included Shandong production areas. The intragroup correlation analysis of 21 quality indicators in 7 production areas showed that single fruit weight, fruit horizontal diameter, fruit vertical diameter, fruit shape index, single core weight, core vertical diameter, nuclear type index, kernel vertical diameter, kernel thickness and kernel shape index showed a high positive correlation (p＜0.01). Among them, kernel yield rate was highly correlated with kernel content rate, and edible rate was highly correlated with single fruit weight, fruit horizontal and vertical diameters, and nuclear shape index (p＜0.01). Through comprehensive analysis of sour jujube kernels in different regions of northern Shaanxi, a comprehensive evaluation system for sour jujube kernel quality was established. The results showed that Shandong, Wubu and Yanchuan scored the highest in the comprehensive quality evaluation of sour jujube. In addition, the fruits, cores and kernels in Shandong production areas were larger, the functional component content of sour jujube kernels in Wubu area was higher and the kernels were larger, and the kernel yield potential of Yanchuan source was relatively high.【Conclusion】The results showed that the wild sour jujube germplasm resources in northern Shaanxi were rich and diverse, and there were certain differences in the quality of wild sour jujube kernels from different origins. Therefore, in the process of wild sour jujube product development and quality control, the appropriate wild sour jujube origin can be selected according to different needs to improve the quality and market competitiveness of the product. In summary, through a comprehensive analysis of the core quality indicators of wild sour jujube kernels in northern Shaanxi, this study established a wild sour jujube germplasm resource evaluation system, which can provide a scientific basis and data support for the quality evaluation and product development of wild sour jujube kernels in northern Shaanxi, and has certain theoretical and practical significance.