Wheat is one of the most important crops for the diet of people. It is the third most produced crop, it accounts for 20% of the calories and a significant amount of protein consumed worldwide. Diseases on wheat can reduce the yield drastically, which can have a huge impact given the importance of the crop. To protect the crop against diseases caused by fungal pathogens, the plants can be treated with chemicals called fungicides that weaken or kill the fungi. However, fungi can develop resistance against the fungicides which reduces the efficiency and makes it a costly disease prevention method. It is therefore important to implement other strategies, such as increasing the defence mechanisms of the crop itself. Plants have evolved natural defences against several pathogens. Due to the external protection with fungicides and the focus on larger yields, the genes for defence against diseases have been reduced in many commercial wheat cultivars. The plant’s natural defence can be improved by using selective breeding to increase the resistance genes in new cultivars.
One of the fungal pathogens on wheat is Parastagonospora nodorum which kills plant tissue and reduces the growth of the plant. The pathogen makes several proteins which can be poisonous to wheat. Only when these proteins are recognised by the plant, it causes plant cells to die. In a recent study, the resistance of several wheat varieties was tested. The wheat leaves were infiltrated with liquid containing the proteins of the fungus. In susceptible wheat, we could see cell death in the infiltrated area. We tested 30 commercial wheat varieties from Sweden, that are currently grown, and some of them were shown to be susceptible to these proteins. This will be problematic if the pathogen becomes more abundant in Sweden. However, in wheat that is used for breeding new cultivars, we found that most of them were resistant, and one cultivar may be partially resistant. The resistance genes of these cultivars can be used in breeding programs to develop commercial wheat with resistance to this disease. Complete resistance causes a big selection pressure on the pathogen which might lead to changes in the fungus to overcome the plant’s resistance. Partial resistance in wheat might be preferred because it reduces the selection pressure on the pathogen, which means it is less likely to evolve and overcome the resistance. Combined with other disease prevention methods, such as working with clean materials and tools, this can be a sustainable way to grow wheat with minimal damage from pathogens.
The image shows how three wheat varieties have different responses to leaf infiltration with the same fungal proteins.
This article is based on a master’s thesis by Mark Melchior
Bruised Food Club 