How Wheat Cultivars Shape Soil Microbiomes Under Nitrogen Deficiency

Nitrogen (N) deficiency is one of the major limiting factors in crop productivity, especially for cereals like wheat. In a recent study published in Plant and Soil, researchers here at the ARC Research Hub for Smart Fertilisers and collaborators investigated how two wheat cultivars (varieties bred for specific traits) with contrasting nitrogen use efficiency (NUE) interact with soil microbes and root metabolites under nitrogen-limited conditions. The wheat cultivars: Mace (with high NUE) and Gladius (with low NUE).  

Key Findings: Changes in Bacterial Communities 

The study found that the two cultivars exhibited contrasting responses in their associated bacterial communities when exposed to nitrogen deficiency. In Mace, the bacterial composition in the rhizosphere (the soil zone directly influenced by root activity) changed significantly, whereas the root endosphere community (bacteria living inside roots) remained stable. Conversely, in Gladius, it was the root endosphere that showed marked shifts in bacterial communities, with little change observed in the rhizosphere. These cultivar-specific microbial responses suggest that the genetic makeup of wheat influences how it recruits and interacts with beneficial microbes under nutrient stress. 

Further analysis using metagenomics (the study of genes of microbial communities) revealed that Mace’s rhizosphere microbiome under N-deficient conditions showed enhanced functional potential, particularly in genes linked to with bacterial movement, nutrient sensing, and cell development. These traits help bacteria colonise roots and form beneficial associations. Such traits were not observed in Gladius, indicating that Mace may be better equipped to attract and support helpful microbes that can alleviate nitrogen stress. 

A notable four-fold increase in octadecanoic acid, also known as stearic acid, was also found for Mace in N-deficient conditions, while no such changes were observed for Gladius. This finding highlights the gene-specific difference in metabolic processes between the two cultivars and suggests the potential role of stearic acid in shaping the bacterial community in the rhizosphere of Mace.  

Why this Matters 

This study highlights the importance of considering plant genotype when developing strategies to enhance crop performance under low-input conditions. The ability of certain wheat cultivars to alter their root exudates and microbial associations in response to nitrogen deficiency could be harnessed to reduce reliance on synthetic fertilisers. Furthermore, the identification of metabolites like stearic acid as potential microbial attractants provides a promising target for the development of next-generation biofertilisers that work synergistically with plant metabolism. 

Read the full paper here: https://link.springer.com/article/10.1007/s11104-024-07048-0