| China has not only limited per capita arable land and large area of marginal land,but also faces the threat of the cultivated land degradation due to intensive cultivation for high yielding.To ensure food security and safety,screening and cultivation of the crop varieties those are able to adapt low-and medium-yielding soils is an important way to sustainable agricultural development.Saline-alkali soil and acidic soil are typical low-and medium-yielding marginal soil.High sodium ion(Na~+)in the saline-alkali soil and low potassium(K~+)in the acidic soil limit crop production.Rice is a staple food crop with moderate tolerance to saline and acidic stress among major crops.Since high K~+in plants can commonly alleviate Na~+toxicity,it is important to screening the germplasm resources of rice for breeding the varieties of efficient K~+uptake and utilization and resistance to salinity soil.In this study,multiple germplasm resources with rich genetic diversities were collected and used for screening the K~+efficient and salinity tolerant rice materials.The rice germplasm includes 229 lines of multi-parent advanced generation inter-cross(MAGIC)DC1 populations,210 lines derived from Southeast Asian(SEA)population,18 and 21 lines with single nucleotide polymorphisms(SNPs)in the promoter and encoding regions of potassium transporter genes Os HAK1 and Os HAK5,respectively.These materials were evaluated for K~+uptake efficiency and salt tolerance under different K~+supply and salt treatments.The hydroponic experiment was conducted for evaluating their tolerance to K~+starvation and salt stress at seedling stage,while the soil pot experiment with and without K~+fertilization and salt treatment was conducted for screening K~+efficient rice materials during entire growth stage.The main results obtained in this study are summarized below:1.The individual lines of the DC1 and SEA populations show great differences in their tolerance to salt stress at seedling stage.The mortality rate,root and shoot biomass accumulation,K~+and Na~+concentration and K~+/Na~+ratio in the plant were analyzed after the treatment of 150 m M Na Cl for 23 days in a hydroponic experiment.Based on the screening and evaluation,the materials including XY3,XY32,XY36,XY41,XY52,XY54 and XY70of DC1 population and XH18,XH21,XH45,XH107,XH177 of SEA population showed the stronger salt resistance and were selected as candidate germplasm for further evaluation.2.Several lines showing double elite traits in the tolerance to salt stress and K~+deficiency were isolated in the hydroponic experiments.All the materials of DC1 and SEA populations,the lines with SNPs of Os HAK1 and Os HAK5 genes were grown at the nutrient solution containing 0.3 m M K~+and 20 m M Na Cl for 3 weeks.There were four,five,seven and eight lines from the DC1 population,SEA population,the materials with natural variation of Os HAK1 and Os HAK5,respectively,which exhibited better growth performance under the double stress treatment of salt and low K~+supply at the seedling stage.3.Several elite materials among the selected germplasms in above hydroponic experiments were further isolated in soil pot experiment for entire growth stage.The parameters used for indicating the growth performance under double stresses of salt and limited K~+supply were plant height,available tiller number,grain to straw ratio and final grain yield per plant.In comparison to local high yield cultivated rice Wuyunjin#7 and highly salt tolerance cultivar Yandao#830,two DC1 lines,three SEA lines,one Os HAK1 line and one Os HAK5 line showed the better growth performance at entire growth and development stage,demonstrating their great potential for breeding K~+efficient and salt tolerant rice cultivars.In summary,this study successfully obtained several elite high yield rice materials with the traits of salt tolerance and higher K~+uptake efficiency.The lines need to be further evaluated in paddy field before being used for breeding elite rice cultivars through molecular marker assistance. |
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