College of Natural Resource and Environment, Northwest A and F University, 712100 Yangling, Shaanxi, China; and Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, K1A 0C6 Ottawa, Ontario, Canada.
Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, K1A 0C6 Ottawa, Ontario, Canada.
Funct Plant Biol. 2021 Jul;48(8):755-765. doi: 10.1071/FP20263.
Preliminary studies observed a lower growth activity during the vegetative stage with higher growth attributes at the pod-filling stage among the high nitrogen (N) utilisation efficiency (NUtE) oilseed rape (Brassica napus L.) genotypes, compared with the low NUtE genotypes. Therefore, we hypothesised that there would exist a critical growth stage when distinctive phenotypic traits are exhibited to regulate yield formation and NUE. A field experiment and a hydroponic culture were conducted to characterise the differences in shoot and root physiological indicators of the high and low NUtE oilseed rape genotypes at seedling, bud, bolting, flowering and pod-filling stages. We found that flowering was the critical period when the reverse growth habit occurred between high and low NUtE genotypes. The high NUtE genotypes displayed larger values of root traits, stronger N uptake kinetics parameters, higher activity of leaf glutamine synthetase (GS) and glutamate synthetase (GOGAT), larger SPAD values and net photosynthetic rate, ultimately leading to higher seed yield and NUE. Our results indicate that flowering is the critical growth stage to distinguish the high from low NUtE oilseed rape genotypes, and plant breeders may focus on selecting root and shoot phenotypic traits from flowering stage onwards to achieve both high yields and NUE for oilseed rape genotypes.
初步研究观察到，与低氮利用效率（NUE）油菜基因型相比，高氮利用效率（NUE）油菜基因型在营养生长阶段的生长活性较低，而在荚果填充期的生长属性较高。因此，我们假设在调控产量形成和 NUE 方面，存在一个表现出独特表型特征的关键生长阶段。本研究通过田间试验和水培试验，对苗期、芽期、抽薹期、花期和荚果填充期高氮利用效率和低氮利用效率油菜基因型的地上部和地下部生理指标进行了特征描述。研究发现，花期是高氮利用效率和低氮利用效率基因型之间发生反向生长习性的关键时期。高氮利用效率基因型表现出较大的根特性值、较强的氮吸收动力学参数、较高的叶片谷氨酰胺合成酶（GS）和谷氨酸合成酶（GOGAT）活性、较大的 SPAD 值和净光合速率，最终导致更高的种子产量和 NUE。研究结果表明，花期是区分高氮利用效率和低氮利用效率油菜基因型的关键生长阶段，植物育种家可能需要从花期开始选择根和地上部表型特征，以实现油菜基因型的高产和 NUE。
