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Fungus-resistant wheat: basic research

Smut fungi infest wheat and other types of grain. They then spread to the next generation of crops through the seeds. Scientists from the Swiss Federal Institute of Technology in Zurich have developed a new concept that enables wheat plants to protect themselves against such diseases by transferring a natural defense mechanism which occurs in maize, to wheat.

Trials in the Üplingen Plant Science Garden should provide fundamental insight into how this resistance method works.

Loose smut: a clever parasite

Loose smut completes one life cycle each year. Infested plants are not openly recognised as such at first. It is only when the crop’s ears have formed that a brownish-black mass of spores can be seen. These spores are spread by wind and rain. When a plant becomes infested, the fungus penetrates the developing grain. If this is sown the following growing season, the fungus grows along with the germinating plant until it again produces a mass of black spores on the ears.

Wheat seed is routinely treated to prevent this fungal disease. Breeding a resistant wheat variety is difficult as there are no parental species with suitable resistance genes available that could be crossed with cultivated wheat. Some resistance genes have been identified, but they are effective only against certain types of smut fungi.

Smut fungi are not a big problem in Europe, but are more problematic in some developing countries. Small farmers in those countries cannot afford to buy expensive seed each year, and so use part of their harvest for sowing the following year. If smut-contaminated grains are among the lot to be sown, the farmers inadvertently contribute to the rapid spread of fungal disease and an accumulation in their own crops. The International Maize and Wheat Improvement Center (CIMMYT) estimates that smut fungi is responsible for between five and ten percent of harvest losses worldwide.

Research live: wheat - resistant to smut fungi?

 

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Field tests under realistic conditions

Initial tests in the greenhouse and field trials in Switzerland have shown that the concept works and that fungal infections can be reduced. Initial expectations of scientists were confirmed, namely that only the harmful fungus was inhibited, and not other fungi or microorganisms in the soil.

Tests in the Plant Science Garden are being carried out primarily to see if the new resistance to smut fungi is effective in different environmental conditions. Two conventional wheat varieties and the lines from these varieties which possess the new protection concept are being grown on tiny plots at Üplingen. In all plots, part of the seeds were infested with loose smut.  It will be seen how the wheat plants behave when faced with the fungal infection. The strength of the plant's resistance can be measured by how heavily the test plants are infested in comparison to the conventional control plants.

The new fungus-resistant transgenic wheat is a prototype that will not be put on the market in this form. Findings resulting from tests in the Plant Science Garden will be used as a basis for further development of fungus-resistant crops.

Date: 2011