Student - November 30, 2006

Barley resistance has genetic pin code

Wageningen researchers have made a genetic map of the barley plant, which indicates more precisely than previous maps where the hereditary resistance to the fungus disease barley leaf rust is located. The result is remarkable, says Dr Rients Niks of the Plant Breeding Group.

‘In each barley variety there are three to five genes that determine how much resistance the plant has against the fungus,’ says Niks. ‘What was surprising was, when we compared six varieties, we noticed that the resistance of was based on a different combination of similar genes. In total we found almost twenty locations in the genome that are connected with resistance.’

Barley is still an important crop in Europe as it is a key ingredient in animal feed and beer. This is one reason why plant scientists are keen to do research on barley and barley leaf rust, a fungal disease that barley suffers from. Another reason is that barley is genetically a little simpler than wheat, but can be used as a model for wheat. In addition, barley leaf rust is also used as a model for other plant diseases such as mildew, wheat rust and sunflower rust.

‘All the diseases are caused by specialised fungi, that mostly on affect one or two plant types,’ explains Rients Niks. ‘Barley leaf rust is not a terribly important disease. Others, such as groundnut rust and sunflower rust, cause far more damage.'

This is the reason for Thierry Marcel’s research. Marcel will obtain his PhD in May 2007, and Niks is one of his supervisors. Marcel is examining the resistance to barley leaf rust in a number of barley plants with different genetic composition. Part of his research will be published soon in the journal Theoretical and Applied Genetics.

What happens at molecular level when barley leaf rust enters the cells of a barley plant is not yet known. What is clear is that pathogens can infect the plant if they can first disable the resistance system. The genetic map shows which parts of the cell are involved in the resistance system.

The large number of locations on the genome that are involved in resistance to barley leaf rust inspired Niks to develop his ‘pin code theory’ ‘It’s a metaphor that occurred to me, that helps me to understand how the fungus can enter the cell. The twenty locations in the DNA correspond to a number code, of which you have to type in a minimum number correctly in order to enter a building before the alarm goes off. If the fungus has the right code in its genome, it will be successful. Otherwise not.’