Adverse Effects of Long-Term Continuous Girdling of Jujube Tree on the Quality of Jujube Fruit and Tree Health

In order to improve fruit yield, girdling technology is widely used in fruit production. However, in the practice of Hui jujube planting in Southern Xinjiang, it was found that the jujube fruit quality declined and the health problems and death rate of jujube trees increased after jujube trees have been girdled continuously for many years, which seriously affected the economic benefits of jujube planting. So, this study was carried out to explore the specific influence law of continuously jujube-tree girdling for many years on the main nutrients (soluble solid, protein, total acid, vitamin C, total sugar, fat and so on), physical quality attributes (single-fruit weight, hardness and geometric-mean diameter) of jujube fruit and tree health. Through the detection of the nutrients of jujube fruit, it was found that the long-term girdling of jujube trees significantly reduced the main nutrients of jujube fruit. The total sugar and reducing sugar content of jujube-fruit samples from the trees without girdling were 134.23% and 109.62% of the corresponding indexes of jujube-fruit samples from girdled ones, respectively; furthermore, the sugar–acid ratio of jujube samples from the girdled trees was 149.95, while the sugar–acid ratio of fruit from non-girdled trees reached 183.78. Moreover, the protein content of fruit from non-girdled trees was 5.91% higher than that of fruit from girdled ones. In addition, the single-fruit weight, hardness and geometric-average diameter of jujube from non-girdled jujube trees were 20.25%, 13.31% and 20.21% higher than those of jujube from girdled ones, respectively. Moreover, microstructural analysis of the callus and the newly formed phloem showed that the adverse effects of girdling on the phloem function were persistent and permanent. It was also found that jujube-tree girdling can also cause damage, to a certain extent, to the xylem around the girdling wound. The above research results further explained the internal cause of jujube-tree death caused by long-term continuously jujube-tree girdling. The results of this study can provide some scientific basis for the effective application of fruit-tree-girdling technology in fruit production.