Resistant mushrooms on the rise

70 percent already insensitive to spray

Leaf-thirsty wheat BBA
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Anti-spill-resistant harmful fungi are spreading more and more in the fields. A European research group has already found 70% resistance to the commonly used plant protection product in the pathogen of leaf drought in wheat.

Fungal diseases are a common problem in agriculture. The mild winter this year provides ideal conditions for the propagation of certain harmful fungi in cereals, such as the leaf drought disease in wheat. The result: The fungal attack leaves the leaves of the wheat plant wither and die. Thus, an effective photosynthesis is no longer possible, the plant - and especially the grain - receives too little nutrients. Yield losses by the so-called "K├╝mmerkornbildung" in the amount of up to 30 percent are not uncommon.

Increase in drug resistance

So far, these mushrooms could be effectively controlled with pesticides. However, the results of a three-year European research project involving twelve scientific institutions from seven countries are alarming. Because the experts, among them scientists from the Federal Biological Research Center for Agriculture and Forestry (BBA), are seeing a steady increase in fungal strains that are resistant to the active substance group of strobilurins as well as triazoles. Fungicides of both classes have been the key to successfully eliminating fungal diseases.

Point mutation in the genome

Responsible for the Strobilurin resistance is a point mutations in the genome of the fungi, which has been detected both in the pathogens of the leaf drought Septoria tritici and Drechslera tritici-repentis, DTR short. Now the researchers have identified another minimal change in the genome, which causes the strobilurins can no longer fight the fungus so effectively.

"The special feature is that we already find strains of the DTR leaf spot pathogens that already have both changes in the genome, " reports Bernd Rodemann from the Federal Biological Research Center (BBA) in Braunschweig. The scientist has tested various combinations of agents in field trials as well as determined the resistance of fungi in laboratory experiments. display

Resistance at 70 percent

Accordingly, the degree of resistance of Septoria tritici is already more than 70 percent, so that, according to Rodemann, a loss of efficacy of all strobilurins in Germany is to be reckoned with over this pathogen. In addition, he and his colleagues report the first signs of decreasing septoria sensitivity to triazoles.

Since spring 2005, there has also been evidence from abroad of decreased sensitivity of DTR to strobilurins, which is now confirmed by the evidence of point mutations. According to the experience of the researchers so-called contact agents in the control of both types of fungi play an important role. In this case, a special protective layer on the leaves prevents fungi spores from germinating on the surface from germinating.

(Federal Agency for Agriculture and Forestry (BBA), 22.02.2007 - NPO)