Effect of salinity stress in Setaria viridis (L.) P. Beauv. accession A10.1 during seed germination and plant development

ABSTRACT Setaria viridis (L.) P. Beauv. is a species proposed to be used as model plant in reverse genetics studies for the validation of gene function. Soil salinity is a recurring problem present in more than a 100 countries worldwide, and approximately 20% of the agricultural land in the world has saline and/or sodium soils. Saline stress affects all the main processes of the plant, such as germination, growth, and, consequently, the yield. The present study aimed at determining the tolerance levels of S. viridisA10.1 to saline stress and identify its potential as a model plant to validate salt-tolerance candidate genes/alleles as well as promoter sequences from salt-responsive genes. In an initial experiment, the seeds of the plant were sown on a germination medium containing an increasing concentration of NaCl (0, 30, 60, 90, 120, or 150 mM), and maintained there during the initial growth stage; and, in another experiment, the plants at the vegetative growth stage were submitted to increasing doses of NaCl (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0g per 100g of the substrate). The germination rate was found to be affected a little by the salinity, while the seedlings development was impaired right after germination. Plant in the vegetative growth stage experienced a reduction in the evapotranspiration rates and pigment levels, along with an impairment in the system of capture and use of light, and a decrease in the leaf gas exchange rates, resulting in less accumulation of dry and fresh plant biomass proportional to the salt dose used. Plants started to die within a week at doses ≥19.4 dS/m. In conclusion, A10.1 is a glycophyte plant with some level of salt-tolerance and might be used as a model plant to validate salt-tolerance candidate genes/alleles, as well as promoters salt-responsive genes, depending on the right combination of plant age and level of stress. As seed germination is affected only little by salt stress at NaCl doses of about 15 dS/m or less, A10.1 might not be used to validate genes/alleles with a putative role regarding this trait.摘要 青狗尾草（Setaria viridis (L.) P. Beauv.）被提议作为反向遗传学研究中验证基因功能的模式植物。土壤盐渍化是全球100余个国家普遍存在的农业难题，全球约20%的农用地分布有盐渍化或钠质化土壤。盐胁迫会干扰植物的核心生理过程，包括种子萌发、生长发育，最终影响作物产量。本研究旨在测定青狗尾草A10.1品系对盐胁迫的耐受水平，并评估其作为模式植物，用于验证耐盐候选基因/等位基因以及盐响应基因启动子序列的潜力。在初始萌发实验中，将该植物种子播种于含梯度浓度氯化钠（NaCl，0、30、60、90、120或150 mM）的萌发培养基中，在初始生长阶段持续培养；另一项营养生长实验中，对处于营养生长期的植株施加梯度剂量的NaCl（每100g基质添加0.0、0.2、0.4、0.6、0.8和1.0g）。结果显示，盐浓度对种子萌发率影响较小，但幼苗萌发后的生长会受到显著抑制。处于营养生长阶段的植株，其蒸散速率与色素含量均出现下降，光能捕获与利用系统受损，叶片气体交换速率降低，最终导致植株干物质与鲜重积累量随NaCl剂量升高呈比例降低。当NaCl剂量≥19.4 dS/m时，植株会在一周内开始死亡。综上，A10.1品系属于具有一定耐盐性的甜土植物，可根据植株生长阶段与胁迫强度的合理组合，作为验证耐盐候选基因/等位基因以及盐响应基因启动子的模式植物。当NaCl剂量约为15 dS/m或更低时，盐胁迫对种子萌发的影响极小，因此A10.1品系不适用于验证与该萌发性状相关的候选基因/等位基因。