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Adaptation in fungal populations: Interactions between space, time, and crop genetics

Posted by: Sarina Macfadyen

July 26, 2016

A new visitor to our team, Dr Lydia Bousset, is using empirical studies in Australia to understand the interaction between crop genetics and adaptation in fungal diseases. Dr Bousset, from the Institute of Genetics, Environment, and Plant Protection at INRA in France has worked for many years on the biology of pathogenic fungi in cropping systems. However, despite being able to breed new crop varieties that show resistance to fungal pathogens, there is an alarming amount of change in these populations from year-to-year, that waste the time and money spent on this management strategy.

Visitor Dr Lydia Bousset in a canola field examining lesions on leaves caused by blackleg
Visitor Dr Lydia Bousset in a canola field examining lesions on leaves caused by blackleg

Blackleg, which is caused by the fungus Leptosphaeria maculans, is one of the most serious diseases of the Australian canola industry. The fungus survives on canola stubble that produces spores that can move several kilometres through the air. When the spores land on leaves of newly planted canola crops they cause leaf lesions and later damage the plant stem. Current management is based on resistant varieties and avoiding planting into previous years stubble. But this defensive strategy based on the careful breeding of resistance genes into our canola varieties is under threat from the fungus itself. If the same resistant varieties are cropped in successive years without preventing the transmission of spores from stubble, the fungal population changes over time, with increased frequency of spores able to infect the resistant variety (which thus loses its efficacy).

Whilst Dr Bousset is visiting Australia she is conducting field experiments that will examine the severity of disease symptoms in plants that would be near and far away from infected stubble, and have the same or different genetic makeup as the infected stubble. “We are trying to measure the impact of spatial, and genetic connectivity on the severity of infection and the composition of the resulting pathogen population” said Dr Bousset. These experiments will provide some useful information for how farmers can better manage blackleg, but also provide some much-needed biological information for incorporation into models that describe the process of adaptation in this system. “Joining CSIRO and INRA forces enables us to tackle the challenge of developing reliable means by which landscape-scale theoretical models may be field tested” said Dr. Bousset

We need to examine what is going on between seasons to understand the process of adaptation” – Dr Lydia Bousset

Dr Bousset’s visit is supported by her home institution, INRA, and a 12 month CSIRO Sir Frederick McMaster fellowship. She is working on projects aligned with a GRDC-funded project CSP00192.