| Objective:Sugar beet is one of the main raw materials for sugar production in China,and it is also an important economic crop in northern China.Potassium（K）is an important quality element in the process of plant production.However,the decrease of soil potassium content and the unreasonable application of potassium fertilizer seriously restrict the sugar yield of beet.Therefore,this study takes high-sugar beet and high-yield beet as research objects by using drip irrigation conditions in Xinjiang.Throuth applying different amounts of potassium chloride and potassium sulfate fertilizer,this study investigates the impact of potassium fertilizer type and quantity on beet growth characteristics and sugar accumulation,elucidates the biological and molecular mechanisms underlying different types of potassium fertilizers’effects on beet sugar metabolism,and provides a scientific basis for achieving high yield and quality in sugar beet production.Methods:In the field experiment,two varieties of high-sugar sugar beet and high-yield sugar beet were applied with different amounts of potassium chloride and potassium sulfate(105 kg·hm-2,210 kg·hm-2,315kg·hm-2based on the amount of K2O).A total of 14 treatments were set up in the experiment:no potassium fertilizer（PCK）under high-sugar beet（P）,potassium chloride fertilizer（PKL1,PKL2,PKL3）with different application rates,potassium sulfate fertilizer（PKS1,PKS2,PKS3）with different application rates,no potassium fertilizer（TCK）under high-yield beet（T）,potassium chloride fertilizer（TKL1,TKL2,TKL3）with different application rates,potassium sulfate fertilizer（TKS1,TKS2,TKS3）with different application rates.To clarify the molecular regulation mechanism of different potassium fertilizers on K+accumulation,growth,yield,photosynthetic characteristics,soluble sugar content and sugar metabolism in various organs of sugar beet.Results:（1）The application of two types of potassium fertilizers could increase the yield,sugar content and sugar yield of the two varieties of sugar beet.The yield and sugar yield of sugar beet under potassium sulfate treatment(K2O 210 kg·hm-2)were the highest in two years of experiments,and the most significant impact on the yield and sugar yield of high-sugar sugar sugar beet was 132.02 t·hm-2and 22.14 t·hm-2in the first year,and 116.94 t·hm-2and 19.56 t·hm-2in the second year,respectively.In addition,in terms of root morphology,the maximum root length and width increased by 39.62%and 31.97%under potassium chloride treatment.Under potassium sulfate treatment,root length and root width increased by 35.85%and36.61%respectively.（2）Application of both types of potassium fertilizers improved sugar beet leaf photosynthesis by increasing the number of green leaves and leaf area at all stages of sugar beet fertility,both with potassium fertilizer application(K2O 315 kg·hm-2)with relatively optimal KCl treatment increasing sugar beet leaf area by 4.83%-78.87%,net photosynthetic rate by 5.85%-69.57%and chlorophyll a content by 5.76%-52.07%.Potassium sulfate treatment increased sugar beet leaf area by 4.99%-90.52%,net photosynthetic rate by 7.22%-82.28%and chlorophyll a content by 6.37%-48.22%.（3）The content of soluble total sugar and sucrose in the aboveground part of sugar beet showed an increasing trend with the increase of potassium application.During the root expansion and sugar accumulation stages,the content of soluble total sugar and sucrose in the underground part of sugar beet significantly increased when the potassium application rate of K2O 210 kg·hm-2,the maximum increase of sucrose content was 45.71%under potassium chloride treatment,and 54.02%under potassium sulfate treatment.（4）An average of under potassium chloride treatment,1607 differential genes were up-regulated and1631 differential genes were down-regulated in sugar beet tubers under KCl fertilization treatment,mainly enriched in Phenylpropanoid biosynthesis（PBS）,which up-regulated the metabolites sucrose phosphate synthase（SPS）and sucrose synthase（SS）by increasing the activities of 22.54%and 6.27%of the tubers,respectively.D-galactose（D-Galactose）content;an average of 1230 differential genes were up-regulated and 1141 differential genes were down-regulated under potassium sulfate treatment,mainly enriched in Plant hormone signal transduction（PST）,by increasing 37.51%sucrose phosphate synthase（SPS）and44.77%sucrose synthase（SS）activities in tuber roots.Sucrose content was up-regulated by increasing37.51%Sucrose phosphate synthase（SPS）and 44.77%Sucrose synthase（SS）activities in tubers.Conclusion:Potassium fertilization on both sugar beet varieties enhanced photosynthesis,promoted sugar beet growth,increased sugar beet yield and soluble sugar content,and the effect of high sugar type sugar beet was better than the abundant sugar beet.Potassium fertilization promoted sugar metabolism and increased soluble sugar content in the tubers by up-regulating the SWEET family of sucrose transport proteins and down-regulating the transcription factor FRUCT 5,thereby reducing the metabolite D-Glucose.Potassium chloride treatment increased the sugar content of sugar beet tubers by up-regulating the transcription factor AGAL1,which increased the metabolite D-galactose,and potassium sulfate treatment increased the metabolite Sucrose by up-regulating the transcription factor SUS 6,which ultimately increased the sugar content of sugar beet tubers.The yield and sugar production of sugar beet under potassium sulfate treatment were better than that of potassium chloride. |
