College of Horticulture, China Agricultural University, Beijing, China.
Sanya Institute of China Agricultural University, Sanya, Hainan, China.
PeerJ. 2022 Mar 31;10:e13008. doi: 10.7717/peerj.13008. eCollection 2022.
Dwarfing is a typic breeding trait for mechanical strengthening and relatively high yield in modern apple orchards. Clarification of the mechanisms associated with dwarfing is important for use of molecular technology to breed apple. Herein, we identified four dwarfing apple germplasms in semi-arid area of Xinjiang, China. The internodal distance of these four germplasms were significantly shorter than non-dwarfing control. Their high melatonin (MT) contents are negatively associated with their malondialdehyde (MDA) levels and oxidative damage. In addition, among the detected hormones including auxin (IAA), gibberellin (GA), brassinolide (BR), zeatin-riboside (ZR), and abscisic acid (ABA), only ABA and ZR levels were in good correlation with the dwarfing phenotype. The qPCR results showed that the expression of melatonin synthetic enzyme genes and , ABA synthetic enzyme gene and degradative gene , ZR synthetic enzyme gene all correlated well with the enhanced levels of MT, ABA and the reduced level of of ZR in the dwarfing germplasms. Furthermore, the significantly higher expression of ABA marker genes ( and ) and the lower expression of ZR marker genes ( and ) in all the four dwarf germplasms were consistent with the ABA and ZR levels. Considering the yearly long-term drought occurring in Xinjiang, China, it seems that dwarfing with high contents of MT and ABA may be a good strategy for these germplasms to survive against drought stress. This trait of dwarfing may also benefit apple production and breeding in this semi-arid area.
矮化是现代苹果园机械强化和相对高产的典型育种特性。阐明与矮化相关的机制对于利用分子技术培育苹果非常重要。在此，我们在中国新疆半干旱地区鉴定了四个矮化苹果种质资源。这四个种质资源的节间距离明显短于非矮化对照。它们的高褪黑素（MT）含量与丙二醛（MDA）水平和氧化损伤呈负相关。此外，在所检测的激素包括生长素（IAA）、赤霉素（GA）、油菜素内酯（BR）、玉米素核苷（ZR）和脱落酸（ABA）中，只有 ABA 和 ZR 水平与矮化表型密切相关。qPCR 结果表明，褪黑素合成酶基因 和 、ABA 合成酶基因 和降解基因 、ZR 合成酶基因 的表达与 MT、ABA 水平的增强和 ZR 水平的降低密切相关。此外，所有四个矮化种质资源中 ABA 标记基因（ 和 ）的表达显著升高，ZR 标记基因（ 和 ）的表达降低，与 ABA 和 ZR 水平一致。考虑到中国新疆每年长期干旱，矮化伴高 MT 和 ABA 含量可能是这些种质资源抵御干旱胁迫的一种很好的生存策略。这种矮化特性也可能有利于该半干旱地区的苹果生产和育种。
