A water-soluble polysaccharide from foxtail millet (FM-D1) was isolated and purified through gradient ethanol precipitation and column chromatography. Size-Exclusion Chromatography–Multi-Angle Light Scattering–Refractive Index (SEC-MALLS-RI) and high-performance anion-exchange chromatography (HPAEC) analyses revealed that FM-D1 constitutes a highly purified neutral polysaccharide exclusively composed of glucose as the sugar unit, with a molecular weight of 14.823 kDa. The structural characterization results obtained from gas chromatography–mass spectrometer (GC–MS) and nuclear magnetic resonance spectroscopy (NMR) spectra suggest that FM-D1 primarily consists of a main chain linked by →4)-α-D-Glcp-(1→ and minor quantities of →4,6)-α-D-Glcp-(1→ to form the main chain, with branching mainly composed of α-D-Glcp-(1→ attached to the O-6 position of →4,6)-α-D-Glcp-(1→ sugar residues. Based on these findings, the antioxidant and immunomodulatory activities of FM-D1 were evaluated in vitro. The results indicated that FM-D1 exhibited moderate 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radical scavenging capacity and total antioxidant capacity (TAOC). Furthermore, FM-D1 stimulated macrophage proliferation and inhibited the production of nitric oxide (NO) and inflammatory factors (TNF-α, IL-1β, and IL-6) in lipopolysaccharide (LPS)-stimulated RAW 246.7 cells. Overall, the findings of this study suggest that foxtail millet holds promise as a potential antioxidant agent and immunologic substance in functional foods.

A pivotal food crop in arid and semi-arid zones, proso millet boasts remarkable economic value, making the breeding of stable high-yield varieties critical for industrial sustainability. This study employed a randomized complete block design to conduct a two-year multi-environment trial on nine new varieties across six representative spring-sown test regions in China. Analytical tools, including additive main effects and multiplicative interaction (AMMI) biplots, AMMI stability values (ASV), genotype and genotype × environment (GGE) models, and genotype by yield–trait (GYT) biplots were utilized to assess genotype–environment (G × E) interactions and screen superior genotypes. AMMI variance analysis showed extremely significant effects of genotype, environment, and G × E on yield traits (p < 0.01). G × E principal component analysis identified JS8, PS3, PS6, and PM4 as dominant genotypes. Based on ASV indices, varietal stability rankings were PS5 > YS13 > JS8 > PS3 > PS6 > PM4 > others. GGE analysis indicated PM4 had the broadest adaptability across tested environments, while JS15 exhibited specific adaptability in Datong. Huairen and Shuozhou were validated as ideal testing environments via an ideal environment plot. GYT biplots further confirmed that YS13, JS15, PS3, and PM4 excelled in comprehensive yield–trait combinations. These findings offer a scientific foundation for ecological adaptability evaluation, breeding material selection, and commercial variety promotion.