Abstract Skin cracking limits fruit quality and marketability. Suggested causes are environmental conditions, orchard management, and failure of the skin to resist surface tension due to fruit expansion. Fruit skin is made up of epidermis cells and cuticular matrix. Theoretical and experimental studies of skin mechanics, together with anatomical and molecular comparisons of cracking-susceptible vs. tolerant genotypes, suggest that increased cuticle thickness, high epidermal cell density and strong adhesion between neighboring cells are associated with cracking resistance. Calyx-end cracking disorder in apple is treated with a mixture of gibberellic acids 4 and 7 (GA4 + 7) and the cytokinin 6-benzyladenine (BA) early in fruit development. The treatment not only significantly reduces cracking incidence in the orchard, it also provides information on the cellular and molecular factors determining fruit-skin resistance to growth strain. BA + GA4 + 7 application results in an immediate increase in epidermal cell density that is maintained until fruit maturation. Moreover, the epidermal cells form clusters within the cuticular matrix, which may strengthen the cuticle by adding more cell-wall components and may enhance crack repair. Skin anatomical modifications are complemented by the expression of genes associated with epidermal cell patterning and cuticle formation. Gene-networking analysis supports the interaction between cell-wall synthesis, cuticle-formation, and GA-signaling gene clusters. Overall, data suggest that BA + GA4 + 7 treatment does not modify developmental cues, but promotes or enhances the innate developmental program. This review presents data on BA- and GA4 + 7-induced skin modifications that complement previously suggested models for cracking resistance in fruit. Knowledge gained on apple fruit skin traits may be applied to control cracking in other fruit as well.

中文翻译：

---

通过塑造表皮性状来控制水果开裂——以苹果为例

摘要 表皮开裂限制了水果的质量和适销性。建议的原因包括环境条件、果园管理以及由于果实膨大导致果皮无法抵抗表面张力。果皮由表皮细胞和表皮基质组成。皮肤力学的理论和实验研究，以及对开裂易感基因型与耐受基因型的解剖学和分子比较，表明增加的角质层厚度、高表皮细胞密度和相邻细胞之间的强粘附与抗开裂性有关。在果实发育早期，用赤霉酸 4 和 7 (GA4 + 7) 和细胞分裂素 6-苄基腺嘌呤 (BA) 的混合物治疗苹果的花萼末端开裂障碍。该处理不仅显着降低了果园开裂的发生率，它还提供有关决定果皮对生长应变的抗性的细胞和分子因素的信息。BA + GA4 + 7 应用导致表皮细胞密度立即增加，并保持到果实成熟。此外，表皮细胞在表皮基质内形成簇，这可以通过添加更多细胞壁成分来增强角质层，并可以增强裂纹修复。与表皮细胞模式和角质层形成相关的基因表达补充了皮肤解剖结构的改变。基因网络分析支持细胞壁合成、角质层形成和 GA 信号基因簇之间的相互作用。总体而言，数据表明 BA + GA4 + 7 治疗不会改变发育线索，但会促进或增强先天发育程序。本综述提供了 BA 和 GA4 + 7 诱导的皮肤修饰数据，这些数据补充了先前建议的水果抗裂模型。获得的关于苹果果实表皮特性的知识也可用于控制其他水果的开裂。