不同驯化阶段谷子对氮胁迫的生理响应及耐低氮综合评价

Comprehensive evaluation of physiological responses and low nitrogen tolerance of foxtail millet at different domestication stages

  • 摘要: 提高作物耐贫瘠能力对于提高边际土地利用率具有重要意义。本试验选用3个不同驯化阶段(野生种、农家种和育成种)的24份谷子材料, 采用水培方法, 设置5个低氮浓度梯度处理0.05 mmol·L−1 NH4NO3 (N1)、0.1 mmol·L−1 NH4NO3 (N2)、0.2 mmol·L−1 NH4NO3 (N3)、0.4 mmol·L−1 NH4NO3 (N4)和1.0 mmol·L−1 NH4NO3 (N5), 以探究低氮胁迫对谷子生长发育的影响, 比较不同基因型谷子的综合耐低氮能力并鉴定高效的生理筛选指标。研究发现, 相对N2处理, N3处理3个驯化阶段谷子材料的多个生理指标(除旗叶叶绿素和根冠比外)均显著增长; 随施氮浓度的增加, 野生种的株高、地上部干重、旗叶叶面积和地下部干重在N3达最大值后迅速趋于稳定, 但农家种与育成种的相应指标则随氮浓度增加而增加, 说明驯化提高了谷子对氮素需求的饱和阈值。基于耐低氮系数综合评价发现, 野生种的耐低氮性优于农家种和育成种; 主成分分析(PCA)揭示, 在低氮胁迫下, 野生种与农家种、育成种的生理表型均存在明显差异, 其中地上部干重、地下部干重和根体积在分析中表现出较大载荷值, 在数据变异解释中占据了显著比重, 能够有效反映不同驯化程度谷子的低氮耐受性。这些结果表明驯化降低了谷子对低氮胁迫的耐受性; 地上部干重因其检测便捷且与谷子耐低氮响应紧密相关, 可作为大规模筛选耐低氮谷子品种的首选表型指标。本研究为谷子耐贫瘠品种的高效筛选提供了参考依据。

     

    Abstract: Enhancing crop tolerance to infertile conditions is crucial for improving the utilization rate of marginal lands. In the current study, 24 foxtail millet samples from three different stages of domestication (wild, landrace, and cultivar) were selected. A hydroponic setup with five low nitrogen concentration gradients was employed 0.05 mmol·L−1 NH4NO3 (N1), 0.1 mmol·L−1 NH4NO3 (N2), 0.2 mmol·L−1 NH4NO3 (N3), 0.4 mmol·L−1 NH4NO3 (N4), and 1.0 mmol·L−1 NH4NO3 (N5), to compare the comprehensive low-nitrogen tolerance ability among the different genotypes of foxtail millet and to identify efficient physiological indicators for germplasm resource screening. This study aimed to gain a deeper understanding of the tolerance of foxtail millet to low-nitrogen stress at different stages of domestication, providing an important preliminary basis for the exploitation of foxtail millet germplasm resources and genes resistant to low-nitrogen. Our findings showed that all the tested physiological indicators, excluding chlorophyll content of flag leaf and root-to-shoot ratio, from the three domestication stages of foxtail millet showed significant increases in the N3 treatment compared to that in the N2 treatment. However, the plant height, aboveground dry weight, flag leaf area, and underground dry weight of the wild species reached their maximum values at N3 and then stabilized, whereas those indicators from landrace and cultivar species continued to increase. Wild species have a lower demand for nitrogen compared to that in landrace and cultivar species, suggesting that low nitrogen tolerance in foxtail millet has been reduced during domestication and breeding, and the threshold of nitrogen concentration required to maintain normal growth has been increasing. Based on a comprehensive evaluation using the nitrogen tolerance coefficient, it was observed that wild species had better nitrogen tolerance than landrace and cultivar species. Principal Component Analysis (PCA) revealed significant differences in the phenotypes between wild species, landraces, and cultivar species under low nitrogen stress, with aboveground dry weight, underground dry weight, and root volume showing high loadings and accounting value for a significant proportion of the data variance. Thus, the physiological indicators and results derived from the PCA effectively reflect the varying degrees of low-nitrogen tolerance exhibited by foxtail millet across different domestication levels. These results demonstrate that domestication reduces the tolerance of foxtail millet to low nitrogen stress. Aboveground dry weight, because of its convenient detection and close correlation with foxtail millet response to low nitrogen, can be used as a preferred phenotypic indicator for large-scale screening of low-nitrogen-tolerant foxtail millet varieties in the future. Our study provides a reference for efficient screening of foxtail millet varieties under infertile conditions.

     

/

返回文章
返回