Untargeted Metabolomics of Root Exudates of Wheat Varieties Cultivated under Phosphorus Stress in the Indo-Gangetic Plains of India

Aims-. Root exudates are a vital interface between plants and soil. Their stress adaptive untargeted metabolomic profiling offers insights into nutrient acquisition strategies. The present study compares root exudates of wheat grown under two experimental conditions- P-amended and P-starved conditions. Methods - Root exudates of wheat varieties (cultivars HD3086 and PBW725 and landrace LC306) were profiled using LC-MS/MS-Q-ToF. They were sampled at different developmental stages of the plant- 20-25 days after sowing (DAS), 60DAS and 90DAS and at flowering stage. Results- A total of 553 compounds were detected. Fatty acids, carbohydrates, amides increased significantly under P-starvation. Compounds having dual role in metabolism and P-starvation mitigation were detected consistently in all varieties in both experimental conditions. These included apiin, maltotriose, raffinose, neokestose, coniferol, adenine, coumarin and gibberellins. However, differences in exudate composition among varieties was observed. LC306 exuded more of ketones, aldehydes and flavones whereas cultivars exuded more of amides and carbohydrates under P-starvation. HD3086 produced stress-responsive compounds like kauranedioic acid and cannabidiolic acid, PBW725 released growth-defence regulators such as brassinolide and xanthoxin. LC306 exuded antioxidant and protective metabolites like quercetin derivatives and dopamine, collectively supporting nutrient acquisition, stress adaptation and developmental regulation. Compounds reported to facilitate direct phosphorus acquisition such as malic acid, phytol, limonin, aspartic acid, mevalonic acid-5p and allantoic acid were detected. Data submitted to www.ebi.ac.uk/metabolights. Conclusion- Modulation of root exudation is an important strategy for optimizing nutrient use efficiency. Array of compounds recorded in root exudates sampled have potential application in engineering all components of rhizosphere.