Unveiling root growth dynamics and rhizosphere microbial responses to waterlogging stress in rapeseed seedlings

Waterlogging is a major abiotic stress that significantly alters ecological biodiversity and threatens crop growth and productivity. Rhizosphere microbial communities are essential for crop mineral nutrition and can help plants withstand stress. However, little is known about how rapeseed rhizosphere microbes respond to waterlogging and their link with soil nutrient availability and root architecture, and physiology. Thus, this study compared root morphological and physiological traits, soil physicochemical properties, and changes in rhizosphere microbial community composition and diversity using 16S rDNA and internal transcribed spacer (ITS) amplicon sequencing under waterlogging and normal conditions. The waterlogging stress induced a significant decline in root activity, growth characteristics, and content of nitrogen and potassium. In contrast, the phosphorus content of roots and shoots significantly increased. Rhizosphere bacteria richness and evenness decreased under waterlogging stress, which was associated with a significant decrease in soil available nitrogen, phosphorus, and potassium. In contrast, fungal diversity increased under waterlogging, concordant with increased soil organic matter content after five days. Notably, the bacterial phyla Proteobacteria and Firmicutes, and fungal phyla Ascomycota and Basidiomycota were identified as biomarkers under waterlogging. Interestingly, several Plant Growth-Promoting Rhizobacteria, including Pseudomonas and Rhizobium, increased under waterlogging conditions, indicating their potential for enhancing rapeseed mineral nutrition, growth, and tolerance. Besides, harmful fungi such as Fusarium solani increased under waterlogging conditions. Our results enhance our understanding of rapeseed response to waterlogging and the contribution of rhizosphere bacteria and fungi. Moreover, the current study provides theoretical bases for improving rapeseed waterlogging tolerance through soil management.