Ecological competence in the rhizosphere
TL;DR
Framing bioinoculant performance as an ecological invasion problem provides a conceptual foundation for understanding why beneficial effects are often conditional and context-dependent, rather than reflecting inconsistent microbial potential.
Abstract
Modern agriculture increasingly requires biological solutions to enhance crop productivity and resilience while reducing reliance on synthetic inputs. In this context, microbial bioinoculants – beneficial microorganisms that are applied to plants or soils – have emerged as a promising strategy, supported by extensive experimental evidence demonstrating their capacity to promote plant growth, improve nutrient acquisition, and enhance resistance to biotic and abiotic stress. However, despite this apparent potential, bioinoculant performance remains highly inconsistent in natural soils and field conditions, and even well-characterised strains with reproducible effects in controlled environments often fail to deliver reliable benefits under realistic agricultural settings. This inconsistency stems from the fact that bioinoculation is fundamentally an ecological process. Introduced microbes must establish, persist, and function within the rhizosphere – the zone surrounding and including plant roots. The rhizosphere is a densely populated, highly competitive and dynamic environment shaped by fluctuating resources, microbial interactions, and active host regulation. As a result, bioinoculant success depends not only on intrinsic genetic traits, but also on the capacity of the microbe to sense, respond to, and remain compatible with local biotic and abiotic conditions. Framing bioinoculant performance as an ecological invasion problem provides a conceptual foundation for understanding why beneficial effects are often conditional and context-dependent. Rather than reflecting inconsistent microbial potential, variable outcomes emerge from differences in host physiology, microbial community structure, and local environmental constraints. This ecological perspective sets the stage for the experimental chapters of this thesis, which investigate how genetic determinants, physiological plasticity, and ecological context jointly shape the success or failure of root-associated bacteria.