MAIN CONCLUSION Early cytokinin activity and late abscisic acid dynamics during wheat kernel development correspond to cultivars with higher yield potential. Cytokinins represent prime targets for marker development for wheat breeding programs. Two major phytohormone groups, abscisic acid (ABA) and cytokinins (CKs), are of crucial importance for seed development. Wheat (Triticum aestivum L.) yield is, to a high degree, determined during the milk and dough stages of kernel development. Therefore, understanding the hormonal regulation of these early growth stages is fundamental for crop-improvement programs of this important cereal. Here, we profiled ABA and 25 CK metabolites (including active forms, precursors and inactive conjugates) during kernel development in five field-grown wheat cultivars. The levels of ABA and profiles of CK forms varied greatly among the tested cultivars and kernel stages suggesting that several types of CK metabolites are involved in spatiotemporal regulation of kernel development. The seed yield potential was associated with the elevated levels of active CK levels (tZ, cZ). Interestingly, the increased kernel cZ levels were followed by higher ABA production, suggesting there is an interaction between these two phytohormones. Furthermore, we analyzed the expression patterns of representatives of the four main CK metabolic gene families. The unique transcriptional patterns of the IPT (biosynthesis) and ZOG (reversible inactivation) gene family members (GFMs) in the high and low yield cultivars additionally indicate that there is a significant association between CK metabolism and yield potential in wheat. Based on these results, we suggest that both CK metabolites and their associated genes, can serve as important, early markers of yield performance in modern wheat breeding programs.

中文翻译：

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早期籽粒发育过程中的细胞分裂素活性与大田小麦 (Triticum aestivum L.) 的产量潜力和后期 ABA 积累呈正相关

主要结论 小麦籽粒发育过程中的早期细胞分裂素活性和晚期脱落酸动力学对应于具有较高产量潜力的品种。细胞分裂素是小麦育种计划标记开发的主要目标。两个主要的植物激素组，脱落酸 (ABA) 和细胞分裂素 (CKs)，对种子发育至关重要。小麦 (Triticum aestivum L.) 的产量在很大程度上取决于籽粒发育的牛奶和面团阶段。因此，了解这些早期生长阶段的激素调节对于这种重要谷物的作物改良计划至关重要。在这里，我们在五个大田小麦品种的籽粒发育过程中分析了 ABA 和 25 种 CK 代谢物（包括活性形式、前体和非活性结合物）。ABA 水平和 CK 形式的分布在所测试的品种和籽粒阶段之间差异很大，这表明几种类型的 CK 代谢物参与了籽粒发育的时空调控。种子产量潜力与活性 CK 水平 (tZ, cZ) 的升高有关。有趣的是，随着籽粒 cZ 水平的增加，ABA 产量也随之增加，这表明这两种植物激素之间存在相互作用。此外，我们分析了四个主要 CK 代谢基因家族代表的表达模式。高产和低产品种中 IPT（生物合成）和 ZOG（可逆失活）基因家族成员 (GFM) 的独特转录模式还表明，小麦的 CK 代谢与产量潜力之间存在显着关联。