Physiological and Molecular Mechanisms of Sodium Selenite Foliar Spray in Promoting Alfalfa Growth

(Se) is a necessary trace element for human beings and animals. Direct ingestion of inorganic Se is dangerous, and conversion of inorganic Se into organic Se by Se-rich plants can be safely consumed by humans and animals. Alfalfa (Medicago sativa L.) is a legume perennial forage crop with high nutritional value and Se-rich function that can be an effective carrier for Se to enter the food chain. Moreover, an appropriate concentration of Se also has positive effects in promoting alfalfa yield. In this experiment, alfalfa was sprayed with sodium selenite of 100mg/L, and analyzed growth, reproductive, physiological, transcriptomics and metabolomics of alfalfa. Spraying sodium selenite significantly increased the growth rate of alfalfa, and also had significant effects on pollen quantity, pollen viability and seeds number of alfalfa. Moreover, Se treatment significantly affected the contents of chlorophyll, soluble protein, proline and glutathione in alfalfa. In this study, a total of 614 differentially expressed genes and 26 secondary differential metabolites were obtained, in which differentially expressed genes were mainly enriched in signal transduction, biosynthesis of secondary metabolites, lipid metabolism, carbohydrate metabolism and amino acid metabolism. Differential metabolites are mainly enriched in amino acid metabolism, biosynthesis of secondary metabolites, carbohydrate metabolism, cofactor and vitamin metabolism, nucleotide metabolism and so on. The Integrative analysis of the transcriptome and metabolome showed that the related genes were most enriched in phenylpropanoid biosynthesis pathway. In this experiment, we studied the effects of spraying selenium on the growth, reproductive, physiological, transcriptomics and metabolomics of alfalfa, and the transcriptome and metabolic group were integrative analyzed to explore the physiological and molecular mechanism of foliar spraying sodium selenite on the growth regulation of alfalfa, so as to provide theoretical basis for the study of selenium enrichment in alfalfa