Xanthan Oligosaccharide Seed Coating Promotes Wheat Growth and Stress-Related Physiological Reprogramming via Hormone Signaling and Plant-Microbe Associations.

Oligosaccharides are plant immune elicitors with recognized roles in seed germination, root development and stress regulation. However, most studies have focused on single oligosaccharides or the independent effects of rhizosphere microorganisms. The coordinated regulation of plant physiological networks and microbial communities by oligosaccharide-based seed coatings remains poorly understood, especially for xanthan oligosaccharides. Here, using wheat root transcriptomics, rhizosphere 16S rRNA sequencing, and physiological assays, we found that a xanthan oligosaccharide composite seed coating significantly improved germination potential, germination rate and seedling vigor. It promoted root and shoot growth under field conditions, optimized the balance of auxin, gibberellin and abscisic acid, activated endosperm hydrolytic enzymes and accelerated nutrient mobilization. Transcriptomics revealed stage-specific regulation of membrane lipid metabolism, hormone signaling, antioxidant defense, carbon/nitrogen metabolism and ABC transporters. Microbiome analysis showed selective enrichment of beneficial genera (Devosia, Paenarthrobacter, Citricoccus), which were positively associated with root nitrogen metabolism and MAPK signaling. Collectively, the coating promoted wheat growth and was associated with stress-related physiological and molecular responses; however, direct stress-challenge and functional-validation experiments are required to verify stress-tolerance mechanisms.