Adaptive evolution in fungi

Adaptive evolution describes how organisms become better suited to their surroundings over time, as beneficial genetic mutations are carried over to the next generation. The fungal pathogen Mycosphaerella fijiensis, which causes disease in bananas, is ideal for studying this process since it rapidly adapts to changing environments.

An example of adaptive evolution is the emergence of aggressive M. fijiensis strains in response to infection of resistant banana hosts. The EU-funded 'Genetic basis of host adaptative traits in the plant pathogenic fungus Mycosphaerella fijiensis' (GATFUN) project aims to determine which genes are behind M. fijiensis' adaptation to overcome host defences.

Researchers carried out genetic analyses that track changes in the fungus' genome after infecting a host. First, they crossed two strains together that differ in their aggressiveness and analysed their progeny to determine how the aggressiveness traits are passed on.

Next, they evaluated aggressiveness traits of about 100 fungal isolates on different banana varieties displaying various resistance levels. These experiments will reveal which genetic differences account for aggressiveness traits, and how fungi use these differences to adapt to hosts with varying resistance levels.

Determining which genes are being selected by the host to allow M. fijiensis to thrive will aid efforts targeting control of the devastating fungal disease. In addition, this work will contribute to knowledge of how adaptive evolution works in fungi and other organisms.