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Durable disease resistance in wheat: similar molecular defense mechanisms against adapted and non-adapted pathogens?

Final Report Summary - DURES (Durable disease resistance in wheat: similar molecular defense mechanisms against adapted and non-adapted pathogens?)

Plants are constantly attacked by various pathogens. Particularly in agriculture, plant diseases pose a major threat to farmers because they cause yield losses in crops. To ensure food security in the future, it is essential to develop crop varieties that show high levels of disease resistance. The wheat gene Lr34 provides durable and broad-spectrum disease resistance against the four devastating fungal diseases leaf rust, stripe rust, stem rust and powdery mildew. Lr34 has been extensively used in wheat breeding and agriculture for more than a century and no increase in pathogen-virulence towards Lr34 has been observed. Because of its durability and broad-spectrum effectiveness, Lr34 has become one of the most important genes in wheat disease resistance breeding. Despite its importance, the molecular action of this resistance gene is not well understood.
Lr34 encodes for an ATP-binding cassette (ABC) transporter protein. These membrane-bound transporters shuttle various substrates across biological membranes. Thus, the resistance conferred by Lr34 must result from the reallocation of an unknown substrate between cells or different cell organs.
During this project, we studied the evolution and transferability of the Lr34 resistance gene. One major findings is that the Lr34 resistance gene is unique to wheat and only evolved very recently. Closely related crop species such as barley, rice and sorghum do not have Lr34-resistance. By studying wild wheat relatives and old landraces we could show that the Lr34-resistance in wheat evolved less than 8,000 years ago probably in the fields of ancient farmers. We could also show that the Lr34 resistance can be successfully transferred into barley, a close relative of wheat. In barley, Lr34 conferred resistance against the barley-specific diseases barley leaf rust and barley powdery mildew – pathogens that do not attack wheat. The successful transfer of Lr34 between species was a surprising result and has two major implications: 1) The resistance mechanism by which Lr34 confers durable disease resistance is conserved between different species and 2) Lr34 might be used as an important tool to improve disease resistance of barley.
In summary, we gained valuable information about the evolution and function of durable crop resistance. The transferability of Lr34 might serve as an important tool to ensure food security in the future. It has been estimated that food production needs to double until 2050 without the availability of additional arable land.