Analysis of Key Differential Metabolites in Sunflower after Downy Mildew Infection

The sunflower inbred line 33G was used as the experimental material, which was planted in the downy mildew disease nursery and the normal field, respectively, to examine changes in metabolites differences in metabolic pathways, and the mechanism of regulation of metabolic pathways in the process of sunflower susceptible to downy mildew. At the seedling stage, six biological replicates were collected from the leaves of diseased plants in the disease nursery and non-diseased plants in the normal field, respectively (S33G in the disease nursery and R33G in the normal field). The alterations in metabolites and metabolic pathways in susceptible and normal plants were studied by using LC/MS technology. The results demonstrate that in the S33G-R33G comparison group, 679 differentially expressed metabolites are screened, with 294 up-regulated metabolites and 385 down-regulated metabolites, and the differential metabolites are enriched to 58 metabolic pathways. Alkaloids, fatty acids, flavonoids, terpenoids, and polyketones are the most up-regulated differential metabolites, while lipids and lipid molecules, organic oxygen compounds, organic acids and derivatives, and other compounds are the most down-regulated differential metabolites. By comparison, it is discovered that arachidonic acid metabolism, diterpene biosynthesis, purine metabolism, oxidative phosphorylation, α-linolenic acid metabolism, citrate cycle (TCA cycle), nicotinate and nicotinamide metabolic pathways are considerably activated.