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Abstract Climate change is rapidly altering the distribution of suitable habitats for many species as well as their pathogenic microbes. For many pathogens, including vector‐borne diseases of humans and agricultural pathogens, climate change is expected to increase transmission and lead to pathogen range expansions. However, if pathogens have a lower heat tolerance than their host, increased warming could generate so‐called thermal refugia for hosts. Predicting the outcomes of warming on disease transmission requires detailed knowledge of the thermal tolerances of both the host and the pathogen. Such thermal tolerance studies are generally lacking for fungal pathogens of wild plant populations, despite the fact that plants form the base of all terrestrial communities. Here, we quantified three aspects of the thermal tolerance (growth, infection, and propagule production) of the naturally occurring fungal pathogenMicrobotryum lychnidis‐dioicae, which causes a sterilizing anther‐smut disease on the herbaceous plantSilene latifolia. We also quantified two aspects of host thermal tolerance: seedling survival and flowering rate. We found that temperatures >30°C reduced the ability of anther‐smut spores to germinate, grow, and conjugate in vitro. In addition, we found that high temperatures (30°C) during or shortly after the time of inoculation strongly reduced the likelihood of infection in seedlings. Finally, we found that high summer temperatures in the field temporarily cured infected plants, likely reducing transmission. Notably, high temperatures did not reduce survival or flowering of the host plants. Taken together, our results show that the fungus is considerably more sensitive to high temperatures than its host plant. A warming climate could therefore result in reduced disease spread or even local pathogen extirpation, leading to thermal refugia for the host.
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This content will become publicly available on May 23, 2026
Non‐Additive Interactions Between Multiple Mutualists and Host Plant Genotype Simultaneously Promote Increased Plant Growth and Pathogen Defence
ABSTRACT Understanding the impact of microbial interactions on plants is critical for maintaining healthy native ecosystems and sustainable agricultural practices. Despite the reality that genetically distinct plants host multiple microbes of large effect in the field, it remains unclear the extent to which host genotypes modulate non‐additive microbial interactions and how these interactions differ between benign/pathogenic environments. Our study fills this gap by performing a large‐scale manipulative microbiome experiment across seven genotypes of the model legumeMedicago truncatula. We combine plant performance metrics, survival analyses, predictive modelling, RNA extractions and targeted gene expression to assess how host genotype and microbes non‐additively interact to shape plant growth and disease ecology. Our results reveal three important findings: (1) host genotypes with high tolerance to pathogens benefit more from multiple mutualist interactions than susceptible genotypes, (2) only high‐tolerance genotypes retain the same beneficial host performance outcomes from the benign environment within the pathogenic environment and (3) the quality of the symbiotic relationship with mutualists is a strong predictor of host survival against pathogenic disease. By applying these findings towards developing crops that promote synergistic microbial interactions, yields and pathogen defence could be simultaneously increased while reducing the need for toxic fertilisers and pesticides.
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- Award ID(s):
- 1922521
- PAR ID:
- 10638020
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Plant, Cell & Environment
- ISSN:
- 0140-7791
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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