How will plant pathogens adapt to host plant resistance at elevated CO₂ under a changing climate?

Area of Science:

• Plant pathology
• Evolutionary biology
• Environmental science

Background:

• Anthracnose, caused by Colletotrichum gloeosporioides, is a significant disease affecting Stylosanthes scabra pastures.
• Understanding pathogen evolution under changing environmental conditions, such as elevated atmospheric CO2, is crucial for disease management.

Purpose of the Study:

• To investigate the evolution of aggressiveness in Colletotrichum gloeosporioides under ambient and elevated CO2 levels.
• To determine the impact of host plant cultivars on pathogen adaptation and evolution.

Main Methods:

• Field-collected isolates of C. gloeosporioides from 1978-2000 were used.
• Sequential inoculation of two isolates onto two S. scabra cultivars over 25 cycles in controlled environments.
• Experiments were conducted at ambient (350 ppm) and twice-ambient (700 ppm) CO2 concentrations.

Main Results:

• Pathogen aggressiveness increased on both resistant and susceptible cultivars under elevated CO2.
• At ambient CO2, aggressiveness increased steadily, driven by cultivar selection.
• Genetic and karyotype changes were observed but not directly correlated with increased aggressiveness.

Conclusions:

• Elevated CO2 accelerates the evolution of aggressiveness in C. gloeosporioides, enhancing its ability to overcome host resistance.
• Increased pathogen fecundity and a favorable microclimate under elevated CO2 can further promote rapid evolution and disease spread.
• These findings highlight the potential for increased anthracnose impact in future climate scenarios.