Bacterial communities in the rhizosphere of common bean and maize respond distinctly to water deficit

Background and aims

Water deficit induces changes in root traits, which can vary across plant species, while drive the bacterial community in the rhizosphere. This study aimed to evaluate the effects of moderate water deficit on rhizosphere bacterial communities associated with maize and common bean.

Methods

A field experiment was conducted to compare two water regimes based on the soil’s water retention capacity (WRC): a no-deficit condition (80% WRC) and a moderate water deficit (40% WRC). We evaluated the structure, composition, and co-occurrence networks of rhizosphere bacterial communities associated with both plant species.

Results

Water deficit significantly altered the structure of bacterial communities which differed between plant species. In maize, community structure exhibited minimal changes, whereas in common bean, pronounced shifts were observed under water deficit. In maize rhizosphere, Actinobacteriota was more abundant under no-deficit, while Proteobacteria increased under water deficit. In contrast, the common bean rhizosphere showed no significant changes in phylum abundance between water regimes. For both plant species, more bacterial taxa were enriched under no-deficit; however, distinct taxa were enriched under water deficit. Co-occurrence network analysis revealed lower nodes (182) and edges (740) in the maize rhizosphere under water deficit, while the number of edges increased in common bean. Generalist taxa dominated the rhizosphere of common bean (18.1%), while specialist taxa were more prevalent in maize, particularly under no-deficit conditions (24.3%).

Conclusion

Bacterial communities in the maize rhizosphere remained stable under water deficit. In contrast, the rhizosphere of common bean exhibited enhanced microbial interactions under water deficit.