Effects Of Biological Nano Se On Yield And Physiological-biochemical Characteristics Of Foxtail Millet

Experiment 1:Foxtail millet has short growth period,drought resistance,barren resistance and strong stress resistance.It is an important food crop in the agricultural production in the arid and semi-arid areas of northern China.Se is one of the 15 microelements necessary for human body,which can regulate the immunity of human body and is closely related to the healthy life of human body.Increasing Se content in crops is an effective way to reduce Se deficiency in human beings.The effects of SeO₄^2-and SeO₃^2-on the physiological and biochemical effects and yield of crops have been reported in wheat,rice,corn and other major crops,and there are more comprehensive studies on foxtail millet,while there are few studies on the application of nano Se on leaves.The experiment was carried out with the variety of foxtail millet?Setaria italica?Jingu 18and Jingu 20 as the experimental materials.In the field experiment,eight Se levels T0?water control?,T1?Nano Se 15 g/hm2?,T2?Nano Se 30 g/hm²?,T3?Nano Se 45 g/hm²?,T4?Nano Se 60 g/hm²?,T5?Nano Se 45 g/hm²?,T6?Na₂SeO₃ 66 g/hm²?,and T7?Na2SeO3 132 g/hm²?were used to spray Se on the leaves at the early stage of grain filling to study the physiological and biochemical characteristics,yield and Se content in the grains of different concentrations of exogenous Se.In order to provide scientific basis for the production and management of Se rich millet,the change law of the amount and the best application amount of exogenous Se on the leaves of millet were determined.The results are as follows:1.The application of proper amount of selenium on the leaf can increase the yield of two foxtail millet varieties to a certain extent,and increase the Se content in the grain.With the increase of Se concentration,the Se content in the grain also increased first and then decreased.Compared with CK,the two cultivars decreased 8.74%and 9.12%respectively under T7 treatment.Different varieties of foxtail millet have different sensitivity to Se.Spraying 60 g/hm² of nano Se and 66 g/hm² of Na2SeO3 at the filling stage is beneficial to the increase of foxtail millet yield.Nano Se 30 g/hm² had the greatest effect on the Se content of Jingu 18,while 45 g/hm² had the best effect on the Se content of Jingu 20.2.Spraying Se on the leaves during grain filling had some effect on the SPAD value of chlorophyll.With the increase of Se concentration,it first increased and then decreased.The SPAD was the highest in T6,which was very significant difference;under the treatment of nano Se,there was difference among different varieties,and the optimal concentration also changed with the extension of treatment time.The spraying concentration of Jigu 18 was 45 g/hm² of nano Se,and that of Jigu 20 was 60 g/hm²of nano Se.3.The activities of SOD,pod,GSH,GSH-Px and the content of MDA were increased and decreased by spraying exogenous Se on the leaves of foxtail millet at the filling stage.With the increasing of Se concentration,the activity of antioxidant enzymes increased first and then decreased,and the content of MDA decreased first and then increased.Compared with the CK,the highest values of these indexes can be increased by 28.6%,48.12%,42.2%and 33.33%respectively,and the maximum value of malondialdehyde can be reduced by 24.69%.In conclusion,30 g/hm² of nano Se and 66 g/hm² of Na2SeO3 have the greatest influence on antioxidant enzyme activity and malondialdehyde of foxtail millet,prevent the accumulation of reactive oxygen species,reduce the degree of lipid peroxidation,delay aging,and further promote the growth and development of millet.Experiment 2:Jigu 20,a high yield and high quality cultivar,was used as the experimental material to cultivate seedlings in the dry shed of Shandong Academy of Agricultural Sciences,The leaves were sprayed with water,Nano Se?0.33 g/mL?and Na2SeO3?0.167 mg/mL?respectively at the five leaf stage.After 24h of treatment,the samples were taken.RNA-Seq technology was used to sequence the transcriptome of the leaves treated with Nano Se,Nano selenite and untreated millet.The differentially expressed genes were obtained by comparing the transcriptome of different treatments,so as to further understand the molecular mechanism of millet responding to Se and explore the effect of millet on Se In order to provide theoretical basis for the research of Se enriched millet,the key genes of Se metabolism pathway were screened out.The results are as follows:The results showed that 532 and 2121 differentially expressed genes?DEGs?were obtained that related to the stress of Nano Se and Na2SeO3.The research provides candidate genes for future study of the Se tolerant and Se enriched functional genome of foxtail millet.Twelve DEGs were chosen for fluorescent qRT-PCR verification,and the results were consistent with those of transcriptome sequencing.We also screened the related genes in the key metabolic pathways.In the pathways of cysteine and methionine metabolism,thiometabolism,selenide metabolism and glutathione metabolism,Se binding protein 1,cysteine methyltransferase,methionine-?-lyase,glutathione S-transferase and glutathione hydrolase were all up-regulated.We speculated that metabolism of sulfur,selenide and glutathione metabolism were closely regulated with the Se response in foxtail millet.The metabolism of cystine and cysteine methionine are closely related to Se response of foxtail millet.The results of this study lay a foundation for further study on the molecular mechanism of Se response and identification of Se responsive genes in foxtail millet.