Liu Zhiwei, Xue Wentao, Jiang Qijuan, Olaniran Ademola Olufolahan, Zhong Xiaoxian
National Forage Breeding Innovation Base (JAAS), Nanjing, P. R. China.
Institute of Animal Science, Jiangsu Academy of Agricultural Sciences, Nanjing, P. R. China.
Plant Methods. 2024 Jun 19;20(1):94. doi: 10.1186/s13007-024-01225-z.
Salt tolerance in plants is defined as their ability to grow and complete their life cycle under saline conditions. Staple crops have limited salt tolerance, but forage grass can survive in large unexploited saline areas of costal or desert land. However, due to the restriction of self-incompatible fertilization in many grass species, vegetative propagation via stem cuttings is the dominant practice; this is incompatible with current methodologies of salt-tolerance phenotyping, which have been developed for germination-based seedling growth. Therefore, the performance of seedlings from cuttings under salt stress is still fuzzy. Moreover, the morphological traits involved in salt tolerance are still mostly unknown, especially under experimental conditions with varying levels of stress.
To estimate the salt tolerance of cutting propagation-dependent grasses, a reliable and low-cost workflow was established with multiple saline treatments, using Paspalum vaginatum as the material and substrate as medium, where cold stratification and selection of stem segments were the two variables used to control for experimental errors. Average leaf number (ALN) was designated as the best criterion for evaluating ion-accumulated salt tolerance. The reliability of ALN was revealed by the consistent results among four P. vaginatum genotypes, and three warm-season (pearl millet, sweet sorghum, and wild maize) and four cold-season (barley, oat, rye, and ryegrass) forage cultivars. Dynamic curves simulated by sigmoidal mathematical models were well-depicted for the calculation of the key parameter, Salt. The reliability of the integrated platform was further validated by screening 48 additional recombinants, which were previously generated from a self-fertile mutant of P. vaginatum. The genotypes displaying extreme ALN-based Salt also exhibited variations in biomass and ion content, which not only confirmed the reliability of our phenotyping platform but also the representativeness of the aerial ALN trait for salt tolerance.
Our phenotyping platform is proved to be compatible with estimations in both germination-based and cutting propagation-dependent seedling tolerance under salt stresses. ALN and its derived parameters are prone to overcome the species barriers when comparing salt tolerance of different species together. The accuracy and reliability of the developed phenotyping platform is expected to benefit breeding programs in saline agriculture.
植物的耐盐性定义为其在盐胁迫条件下生长并完成生命周期的能力。主要作物的耐盐性有限，但牧草能够在沿海或沙漠地区大片未开发的盐碱地上存活。然而，由于许多草种存在自交不亲和受精的限制，通过茎段扦插进行营养繁殖是主要方式；这与目前基于种子萌发的幼苗生长所开发的耐盐性表型分析方法不兼容。因此，扦插苗在盐胁迫下的表现仍不明确。此外，耐盐相关的形态特征大多仍不清楚，尤其是在不同胁迫水平的实验条件下。
为了评估依赖扦插繁殖的草种的耐盐性，以钝叶草为材料、以基质为介质，通过多种盐处理建立了一种可靠且低成本的工作流程，其中冷层积处理和茎段选择是用于控制实验误差的两个变量。平均叶片数（ALN）被指定为评估离子累积耐盐性的最佳标准。四个钝叶草基因型以及三个暖季型（珍珠粟、甜高粱和野生玉米）和四个冷季型（大麦、燕麦、黑麦和黑麦草）牧草品种的一致结果揭示了ALN的可靠性。通过S形数学模型模拟的动态曲线能够很好地描绘关键参数“盐分”的计算。通过筛选另外48个先前从钝叶草自交可育突变体产生的重组体进一步验证了该综合平台的可靠性。基于ALN表现出极端“盐分”的基因型在生物量和离子含量方面也表现出差异，这不仅证实了我们表型分析平台的可靠性，也证实了地上部ALN性状对耐盐性的代表性。
我们的表型分析平台被证明适用于评估盐胁迫下基于种子萌发和依赖扦插繁殖的幼苗耐受性。在比较不同物种的耐盐性时，ALN及其衍生参数易于克服物种障碍。所开发的表型分析平台的准确性和可靠性有望使盐碱农业育种计划受益。
