Local Thermal Adaptation in an Insect-Transmitted Plant Pathogen: The Role of Virulence Trade-Offs
Monica A Donegan1, Josephine Nuño1, Ranlin Liu2
1Department of Environmental Science, Policy, and Management University of California-Berkeley Berkeley California USA.
Evolutionary Applications
|July 17, 2026
Summary
Bacterial pathogen populations, like Xylella fastidiosa (Xf), show local adaptation to temperature. Strains from warmer climates grow faster but are less virulent in colder regions, impacting disease management.
Area of Science:
- Microbial Ecology
- Plant Pathology
- Evolutionary Biology
Background:
- Local adaptation to temperature in bacterial pathogens is poorly understood.
- Thermal adaptation influences bacterial pathogen virulence, impacting disease management.
- Xylella fastidiosa (Xf) is a significant plant pathogen causing Pierce's disease in grapevines.
Purpose of the Study:
- To investigate local temperature adaptation in Xylella fastidiosa (Xf) populations.
- To compare in vitro growth and in planta virulence of Xf strains from different climate regions.
- To understand the implications of thermal adaptation for Xf virulence and disease management.
Main Methods:
- Compared in vitro growth of Xf strains from cold (Hopland) and warm (Bakersfield) California climates.
- Assessed in planta virulence of Xf strains in reciprocal field experiments.
- Analyzed Xf survival and disease symptoms under different temperature regimes.
Main Results:
- Warmer climate Xf strains exhibited faster growth at suboptimal temperatures (20°C), indicating a lower thermal optimum.
- Colder climate Xf strains showed higher overwinter survival in field experiments.
- Non-local cold-climate Xf strains caused severe symptoms and vine mortality in warmer climates, suggesting a virulence-transmission trade-off.
Conclusions:
- Xylella fastidiosa populations in California are locally adapted to temperature.
- Cold-climate Xf strains display hypervirulence in warmer climates, while warm-climate strains have reduced survival in colder climates.
- Local thermal adaptation influences pathogen virulence phenotypes across landscapes, with implications for disease control strategies.
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