Rhizosphere bacteria promote sustainable crop growth

Sustainable agriculture benefits from ecosystem services provided by naturally occurring soil dwelling microbes that plants recruit into the rhizosphere to create the plant root microbiome. Microbes influence plant growth and resource use efficiency and can improve plant nutrition, health and crop yields whilst minimizing fertilizer and agrochemical use. Key players are the fluorescent pseudomonads, a ubiquitous, diverse and culturable group of rhizosphere bacteria. Beneficial traits include phytohormone effects, nutritional enhancement and protection from pathogens. This project aims to establish the extent to which possession of particular genes by Pseudomonas fluorescens predicts their effects on plant growth and whether the soil ecosystem can be managed by introducing inoculants, as single strains or assemblages.
Rothamsted has a collection of genetically-distinct P. fluorescens isolates from the wheat rhizosphere; genomic sequences are available for 20 which will be screened for genes encoding beneficial and deleterious traits, using standard bioinformatics and molecular tools. Isolates with contrasting traits will be applied (both singly and in assemblages) to crop plants to determine effects on growth, resilience, resource use efficiency, and the ability of the bacteria to compete with each other and indigenous soil bacteria to colonize plant roots and survive in soil.
Hypotheses to be tested in the project:
1. Plants either differentially select rhizosphere microorganisms with beneficial traits, or the process is stochastic and depends on the numbers and diversity of bacteria in the bulk soil
2. Introducing beneficial individual isolates or assemblages can enhance plant growth and allow more efficient use of fertilizers
3. Crop water status affects microbial populations and their interactions with plants