Zhou Zhang-Jie, Zhao Zi-Xuan, Zhou Jing-Jing, Yang Fan, Zhang Jin-Zhi
College of Horticulture and Forestry Science, Huazhong Agricultural University, Wuhan 430070, China.
Institute of Tropical and Subtropical Cash Crops, Yunnan Academy of Agricultural Sciences, Baoshan 678000, China.
Plants (Basel). 2025 Aug 8;14(16):2461. doi: 10.3390/plants14162461.
Macadamia (), and hybrids, a crop of high economic and nutritional importance, faces challenges with low fruit set rates and severe fruit drop. To address this, we investigated the effects of exogenous plant growth regulators (PGRs) and boron fertilizer on the development, fruit set, and yield of the A4 macadamia variety. The study was conducted in 2024 at the Lujiangba research base (China, Yunnan Province). Five treatments were applied during key growth stages: boron (B), brassinosteroids (BR), N-(2-Chloro-4-pyridyl)-N'-phenylurea (CPPU), 6-benzylaminopurine (6-BA), and gibberellic acid (GA). Growth stages include flower bud formation, peak flowering, and fruiting. Our findings revealed that B treatment significantly increased pollen viability (95.69% improvement) and raceme length (23.97% increase), while BR enhanced flower count per raceme (26.37% increase) and CPPU improved flower retention (10.53% increase). Additionally, GA and 6-BA promoted leaf expansion in new shoots, increasing leaf length by 39.83% and 31.39%, respectively. Notably, B application significantly improved total yield (43.11% increase) and fruit number (39.12% increase), whereas BR maximized nut shell diameter (5.7% increase) and individual nut weight (19.9% increase). Furthermore, CPPU and 6-BA markedly improved initial fruit set rates, while GA, BR, and B effectively reduced early fruit drop. Physiological analyses indicated that elevated soluble sugars and proteins in flowers correlated with higher initial fruit set, whereas increased endogenous cytokinin and GA levels improved fruit retention and reduced drop rates. Based on these findings, we propose an integrated approach to optimize productivity: applying 0.02% B at the floral bud stage, 2 mg/L 6-BA at full bloom, and a combination of 0.02% B and 0.2 mL/L BR during early fruit set. This strategy not only enhances yield but also mitigates fruit drop, offering practical solutions for macadamia production.
澳洲坚果（Macadamia）及其杂交品种是具有高度经济和营养重要性的作物，但面临着坐果率低和严重落果的挑战。为解决这一问题，我们研究了外源植物生长调节剂（PGR）和硼肥对A4澳洲坚果品种发育、坐果和产量的影响。该研究于2024年在中国云南省的庐江坝研究基地进行。在关键生长阶段应用了五种处理方法：硼（B）、油菜素内酯（BR）、N-（2-氯-4-吡啶基）-N'-苯基脲（CPPU）、6-苄基腺嘌呤（6-BA）和赤霉素（GA）。生长阶段包括花芽形成、盛花期和结果期。我们的研究结果表明，B处理显著提高了花粉活力（提高了95.69%）和总状花序长度（增加了23.97%），而BR增加了每个总状花序的花朵数量（增加了26.37%），CPPU提高了花朵保留率（增加了10.53%）。此外，GA和6-BA促进了新梢叶片的扩展，叶片长度分别增加了39.83%和31.39%。值得注意的是，施用B显著提高了总产量（增加了43.11%）和果实数量（增加了39.12%），而BR使坚果壳直径最大化（增加了5.7%）和单个坚果重量（增加了19.9%）。此外，CPPU和6-BA显著提高了初始坐果率，而GA、BR和B有效地减少了早期落果。生理分析表明，花朵中可溶性糖和蛋白质含量的升高与较高的初始坐果率相关，而内源细胞分裂素和GA水平的增加提高了果实保留率并降低了落果率。基于这些发现，我们提出了一种优化生产力的综合方法：在花芽期施用0.02%的B，在盛花期施用2 mg/L的6-BA，在幼果期施用0.02%的B和0.2 mL/L的BR的组合。这种策略不仅提高了产量，还减轻了落果，为澳洲坚果生产提供了切实可行的解决方案。
