Generalists and keystone species drive rhizosphere microbial diversity and stability in feral Brassica napus

Brassica napus (rapeseed) is a globally important crop, primarily valued for its oil production. However, feral B. napus in non-agricultural areas remains under-researched. This study aims to examine the roles of microbial generalists and network keystone species in shaping microbial diversity and network stability of feral B. napus. We analyzed prokaryotic, fungal, and eukaryotic communities in the rhizosphere and bulk soil from five grassland sites. The rhizosphere microbial communities differed significantly from those in adjacent bulk soil, showing lower diversity and richness. Pseudomonas brassicacearum (bacterium), Olpidium brassicae (fungus), and Glissomonadida (eukaryote) were predominantly found in the rhizosphere. Inter- and intra-kingdom association occurred almost exclusively within the rhizosphere, with low interconnectivity compared to the bulk soil, and network keystone species served to bridge these connections. Furthermore, structural equation modeling highlighted the role of generalists and network keystone species in maintaining microbial diversity and stability. Feral B. napus selectively influenced rhizospheric generalists, which, along with keystone species, played key roles in determining microbial diversity and network stability, controlling community structure and interspecies interactions.