Identification And Comprehensive Evaluation On Saline-Alkali Tolerance Of Panicum Miliaceum L.

In nature,soil salinization and alkalization often occur at the same time,which seriously affects the yield of crops.Because of the increasing salinization and alkalization in soils,it has been a great threat to crop production.Proso millet is one of the oldest crops in China,which has the characteristics of short growth period,drought tolerance,barren tolerance and so on.It is a pioneer crop to resist drought and prepare for famine,increase multiple cropping income and adjust agricultural planting structure.Therefore,saline-alkali tolerant varieties selection,studying the mechanism of saline-alkali tolerance and excellent genes'excavation have important guiding significance for the improvement of saline-alkali soil and the cultivation of stress-resistant varieties of millet.Researches were conducted with hydroponic culture in incubator in 2018-2019.Thirty-nine proso millet cultivars were screened for saline-alkali tolerance.Saline-alkali tolerant cultivar?Xinjianghongmi?and Saline-alkali sensitive cultivar?Shaan78?were used,and the contents of osmotic regulation substances and ions,antioxidization system of the two proso millet cultivars,leaf ultrastructure of different cultivars of proso millet were analyzed.The major results of the studies were as below:?1?The concentration of Na HCO₃-Na₂CO₃,80 mmol L^-1,could be suitable for saline-alkali tolerance identification of proso millet cultivars.Principal component analysis results showed that germination index,vitality index and alkali damage rate were the most significant factors in this research and are recommended as the main indexes to identify saline-alkali tolerance of proso millet at germination.The analysis showed one of the 39cultivars were highly saline-alkali tolerant Xinjianghongmi,one cultivar was saline-alkali tolerant Mi,fifteen cultivars were medium saline-alkali sensitive e.g.Neimengguhuangqimizi,seventeen cultivars were saline-alkali sensitive,e.g.Yucixiaoheimi,and five were highly saline-alkali sensitive e.g.Andingjinshoushu.?2?Under saline-alkali stress,the contents of proline,soluble sugar,soluble protein of the two proso millet cultivars increased,and the root activity of the two proso millet cultivars decreased.The increases of proline,soluble sugar and soluble protein of leaves of Xinjianghongmi were more than those of Shaan78.The reduction of root activity was less than that of Shaan78.The osmotic adjustment ability of Xinjianghongmi was stronger than that of Shaan78.?3?Under saline-alkali stress,Na⁺content of the two cultivars increased,and the Na⁺content of roots was higher than that of leaves.These showed that roots did well in storing sodium,and could reduce the transportation of sodium to leaves.Under saline-alkali stress,the increases of roots Na⁺content of Xinjianghongmi were more than those of Shaan78,and the increase of leaves Na⁺content of Xinjianghongmi were less than those of Shaan78.The contents of K⁺,Ca²⁺,and K⁺/Na⁺of leaves and roots of the two proso millet cultivars reduced under saline-alkali stress,and the reduction of Xinjianghongmi were less than those of Shaan78.These showed that the ability of selective absorption of Xinjianghongmi was better than that of Shaan78.?4?Under saline-alkali stress,the contents of MDA increased,and the increase extents got higher along with the increase of Na HCO₃-Na₂CO₃concentration.The contents of MDA of the saline-alkali tolerant cultivar Xinjianghongmi were less than those of saline-alkali sensitive cultivar Shaan78.The activity of SOD,POD,CAT,APX of proso millet seedlings improved under saline-alkali stress,and the increases of activity of Xinjianghongmi were more than those of Shaan78.?5?Under saline-alkali stress,chloroplast expansion,increased number of osmiophilic bodies,distortion of Stroma lamella and loose expansion of grana lamellae appeared in the leaf cells of the two millet varieties.Among them,the increase of osmiophilic body number of salt-tolerant variety Xinjianghongmi under saline-alkali stress was less than that of Shaan78,and the damage degree of chloroplast double-layer membrane and cell wall was less than Shaan78.This shows that Xinjianghongmi can better maintain the leaf cell structure and has strong saline-alkali tolerance under saline-alkali stress.