Salt Tolerance And Physiological Biochemical Correspondence To Salt Stress In Xianlajiao Chili Pepper

Soil salinization has become an important problem restricting vegetable production.As an important vegetable crop,the study on salt tolerance of pepper is relatively limited.In particular,the research on Xianlajiao chili pepper as experimental materials has hardly been reported.In this study,the effects of salt stress on seed germination,seedling growth,physiological and biochemical characteristics of seedling leaves,root growth and root gene expression of chilies were studied using Xianlajiao chili pepper variety(strain)as the material.It is expected to explore the mechanism of salt tolerance of Xianlajiao chili pepper.It provides reference and technical support for the study of salt tolerance and the production of Xianlajiao chili pepper under salt stress.In this experiment,20 pepper varieties(strains)were used as materials.NaCl solutions of 50,100,150,200 and 250mmol/L were used for treatment,and distilled water was used as control.The germination rate,germination potential and germination relative salt injury rate of seeds under salt stress were studied.On this basis and with reference to existing studies,salt-tolerant varieties(7301,D1)and salt-sensitive varieties(GX7,102)were selected to carry out studies on the physiological biochemical characteristics and growth of seedling.On the basis of the above studies,salt-tolerant varieties(7301)and salt-sensitive varieties(GX7)were selected for root growth and gene differential expression studies.The main research results are as follows:1.In the seed germination experiment,with the increase of NaCl treatment concentration,the germination rate and germination potential of all test materials showed a trend of low concentration(50mmol/L)to promote seed germination.At high salt concentration(150mmol/L),only a few varieties had germination rates above 50%,among which D1 and D2 had germination rates of 90.0% and 89.3%.The germination rates of JX,XTE,J1 and 7301 ranged from 48.0% to 65.3%.The germination rates of JJ,102,GX7 and GX6 were lower than 10.0%.The highest germination potential was 39% in all materials.However,only 7301 and D1 could germinate in 250mmol/L NaCl solution,and the germination rate was 28.7% and 2.0%,respectively.The germination test showed that 7301 and D1 were relatively salt-tolerant,while GX7 and 102 were sensitive to salt.2.In the seedling growth test,plant height and stem diameter of the four materials allshowed a decreasing trend with the increase of salt concentration.In all treatments where the salt concentration is higher than 100 mmol/L,the plant height and stem diameter of salt-tolerant variety 7301 seedlings were higher than the other three materials,and the difference of most observation points was obvious.3.In terms of physiological and biochemical indexes of seedling leaves,the anthocyanin content,PPO and GR activity of salt-tolerant cultivars 7301 and D1 were higher than those of salt-sensitive cultivars GX7 and 102 when treated with high concentration for20 days.Salt-sensitive varieties accumulated more MDA under NaCl stress,and their plasma membrane permeability was also higher than that of salt-tolerant varieties.The results indicated that the salt damage degree of salt sensitive varieties was higher.4.With the increase of NaCl concentration,the root systems of salt-tolerant variety7301 and salt-sensitive variety GX7 gradually changed from milky white to brown.The root growth of 7301 decreased slightly under high concentration salt treatment,but the root growth of salt-sensitive variety GX7 decreased significantly.The total root length,total root surface area,root tip number and root dry weight of the two varieties all decreased significantly with the increase of salt concentration,but the effect of salt stress on 7301 was significantly less than that on GX7.5.Compared with the control group,the number of differentially expressed genes at 12 h was the largest.GX7 is 4102,and 7301 is 4713.Based on GX7,a large number of genes in7301 root system showed differential expression under NaCl stress.Through GO analysis,the differentially expressed genes related to root salt tolerance were distributed in three GO branches,including cell composition,molecular function and biological process.It involves root morphogenesis,osmotic stress response,glutathione transferase activity and so on.6.Annotation analysis in the KEGG database showed that there were 11 genes that were differentially expressed at all sampling points.Two of them were down-regulated and nine were up-regulated.Three GX7 genes(Capana11g001528,Capana06g001415 and Capana00g000561)were not differentially expressed at three time points.These results suggested that the up-regulated expression of glutathione metabolism,fatty acid metabolism and phagosome might be closely related to the salt tolerance of chilies.