Characterization of DBP contamination in a soil-wheat system and variety-specific tolerance associated with rhizosphere microbial communities

Phthalate esters (PAEs) are a class of widely prevalent environmental pollutants that pose a serious threat to farmland ecosystems and agricultural product safety. The results of this study showed that dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) were the main PAEs in wheat field soils. All six PAEs were detected in various wheat tissues, and DBP exhibited an accumulation pattern during its migration toward the grains. Therefore, using DBP as the stress factor, we successfully screened a strongly tolerant variety RC69 and a sensitive variety ZM7698 from 51 wheat varieties. Greenhouse experiments confirmed that the aboveground biomass of RC69 remained stable under DBP stress, while that of ZM7698 showed concentration-dependent inhibition. Rhizosphere bacterial community structure of RC69 remained stable under DBP stress, but significant shifts in ZM7698, which was manifested in the decrease in the abundance of key taxa such as Proteobacteria and Pseudomonas, and the enrichment of DBP-tolerant taxa such as Gemmatimonadetes. Functional prediction analysis indicated that DBP stress significantly altered the potential ecological functions of rhizosphere bacteria in ZM7698, especially those associated with carbon and nitrogen cycling. This study provides a theoretical basis and a potential technical approach for harnessing rhizosphere microbial regulation to enhance crop stress resistance, offering a promising strategy for the safe utilization of contaminated soils and the clean production of agricultural products.