Abstract:

Objective: This study aims to investigate the phenotypic traits of Ziziphus jujuba var. spinosa fruit in the eastern Taihang Mountains and the environmental driving factors, and to screen out excellent Z. jujuba var. spinosa production areas, so as to provide a scientific basis for the development and utilization of jujube resources. Method: A total of 38 sampling sites with 152 plots were set up in the eastern Taihang Mountains, and the site conditions including altitude and soil pH were assessed. Z. jujuba var. spinosa fruits were collected from each plot, and their phenotypic traits (vertical and horizontal diameters, fruit mass, nutlet, kernel, etc.) were measured. Result: 1) There were significant differences in the phenotypic traits of Z. jujuba var. spinosa fruits among different regions (P < 0.01). Notably, kernel mass (20.86%), kernel rate (19.63%), fruit mass (13.72%), and fresh fruit edible rate (13.35%) had the higher inter-regional variability coefficients. There were correlations among various phenotypic traits. Specifically, the kernel rate showed a highly significant negative correlation with fruit vertical diameter, fruit horizontal diameter, and fruit mass (P < 0.01). 2) Environmental factors were able to explain 56.7% of the variation in the phenotypic traits of Z. jujuba var. spinosa fruits. Altitude (14.2%), latitude (11.8%), soil pH (4.2%), soil moisture content (3.9%), and soil bulk density (3.2%) were the main environmental factors influencing these traits. The kernel rate was significantly positively correlated with altitude (P < 0.01), but significantly negatively correlated with latitude, longitude, and soil moisture content (P < 0.01). Fresh fruit edible rate was significantly negatively correlated with latitude, altitude, longitude, and soil sand content (P < 0.01), and significantly positively correlated with annual average temperature and effective accumulated temperature (P < 0.01). 3) Based on the phenotypic distribution characteristics of Z. jujuba var. spinosa fruits, "fruit-use type" production sites were identified in Boai County and Zanhuang County; "kernel-use type" production sites were found in She County and Linzhou City; "fruit- kernel dual-use type" production sites were located in Yuquanshan Mountain within Xindu District of Xingtai City and Zanhuang County. Conclusion: There is a strong correlation among different phenotypic traits of Z. jujuba var. spinosa fruits, and the kernel rate, and fresh edible fruit rate can serve as important reference indicators in variety breeding and improvement. Phenotypic traits of Z. jujuba var. spinosa, such as kernel rate and fresh edible fruit rate, are greatly influenced by environmental factors. Adjustment of temperature, soil pH, and soil moisture content can be considered as one of the method to increase Z. jujuba var. spinosa kernel and pulp yield.

Key words: Ziziphus jujuba var. spinosa, the eastern Taihang Mountains, fruit phenotypic traits, environmental factors, grey correlation analysis