Fruit cracking is a key problem restricting the development of the jujube (Ziziphus jujuba) industry, and is closely related to the distribution of the wax layer on the surface of the fruit. Three jujube cultivars with different levels of cracking resistance, namely 'Popozao', 'Banzao', and 'Hupingzao', were selected for comparison. Cracks on the cuticular membrane (CM) of 'Hupingzao' widened and deepened during the coloring period. The wax level of highly cracking-resistant 'Popozao' was significantly higher than that of 'Hupingzao' during the fruit coloring period. The fruit wax composition of the three jujube cultivars were quite similar, consisting mainly of alkanes, triterpenoids, aldehydes, amines, phenols, esters, ketones, fatty acids, primary alcohols, and other, unclassified compounds. Fatty acids, primary alcohols, and alkanes were the predominant fruit wax compounds of the three cultivars. We further analyzed the carbon chain length of aliphatic compounds and found that the concentration of fatty acids in 'Popozao' was significantly lower than that in 'Banzao' and 'Hupingzao' during the coloring period. Moreover, C28-30 were the most abundant primary alcohols during fruit development. Highly cracking-resistant cultivar 'Popozao' contains more very-long-chain alkanes and aldehydes (carbon atom >20) than 'Banzao' and 'Hupingzao' during the coloring period. In addition, we assessed the expression levels of 11 genes involved in fatty acid biosynthesis, elongation, and degradation, and in wax biosynthesis. Gene expression analysis indicated that KCS1, CER1, CYP86B1, and CYP86A play crucial roles in wax formation on jujube fruit. In conclusion, fruit cracking was correlated with whether wax synthesis is coordinated with fruit enlargement and'Popozao' has a stronger ability to synthesize very-long-chain alkanes and aldehydes. Understanding the diff ;erences in the cuticular wax and the activities of the corresponding genes in jujube cultivars with different sensitivities to cracking will provide a specific way to prevent fruit cracking.

中文翻译：

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不同抗裂枣品种（Ziziphus jujuba Mill.）的蜡成分和浓度

果实裂果是制约枣（Ziziphus jujuba）产业发展的关键问题，与果实表面蜡层的分布密切相关。选择了具有不同抗裂性水平的三个枣品种，即'爆破枣'、'半枣'和'虎平枣'进行比较。在着色期间，'虎平枣'表皮膜 (CM) 上的裂缝变宽并加深。在果实着色期，高抗裂‘破破枣’的蜡质含量显着高于‘虎平枣’。三个枣品种的果蜡成分非常相似，主要由烷烃、三萜、醛、胺、酚、酯、酮、脂肪酸、伯醇和其他未分类化合物组成。脂肪酸、伯醇和烷烃是三个品种的主要果蜡化合物。我们进一步分析了脂肪族化合物的碳链长度，发现在着色期间，'爆破枣'的脂肪酸浓度显着低于'半枣'和'虎平枣'的脂肪酸浓度。此外，C28-30 是果实发育过程中最丰富的伯醇。高抗裂品种‘爆破枣’在着色期比‘半枣’和‘虎平枣’含有更多的极长链烷烃和醛类（碳原子>20）。此外，我们评估了 11 个参与脂肪酸生物合成、延伸和降解以及蜡生物合成的基因的表达水平。基因表达分析表明 KCS1、CER1、CYP86B1、CYP86A 和 CYP86A 在枣果蜡形成中起关键作用。综上所述，果实裂果与蜡质合成与果实膨大是否协调相关，且‘爆破枣’具有较强的合成超长链烷烃和醛类的能力。了解不同裂果敏感性的枣树品种表皮蜡质的差异和相应基因的活性，将为预防裂果提供一种具体的方法。