How are those data generated?

Each year, we collected diseased leaf samples from Scandinavia, the Baltic area and other countries. Single pycnidium isolates are produced and analysed by sequencing or qPCR. In some case, leaf samples are bulked and analysed using a pyrosequencing approach. This service is often provided by the industry (BASF). The outcome of all of the methods mentioned above is the information to what extent (in per cent) the CYP51 mutation is represented in the local area. The aim of this investigation is to follow the evolution of CYP51 mutation over time and space.

Triazole resistance to Zymoseptoria tritici

After a drop in field performance of the triazoles in many countries, investigations for specific target site mutations have been carried out to see how variable the situation with CYP51 mutations are across a range of countries. Leaf samples or specific isolates have been analysed for CYP51 mutations D134G, V136A/C, A379G, I381V by pyrosequencing and S524T by qPCR or be sequencing. Due to the many mutations and the possible combinations of those, numerous haplotypes are found at different localities. Some common trends in evolution are however seen e.g. S524T is much more widespread in Ireland and UK, reflecting a more intensive use of azoles during many seasons.

Field trials have shown, that strategies where the same triazole is used repeatedly leads to an increase in point mutations like D134G, V136A, and S524T.

Field trials have also shown that by diversifying the strategy including different azoles, SDHIs and the multisite inhibitor like chlorothalonil and Folpet, the selections for specific mutations can be lowered.

The formulated guidelines based on field studies and current literature is to keep the total number of spraying with triazoles down and not to exceed 3 in one season, not to use the same triazole more than twice, and to include products containing other modes of action, like SDHI’s and multi-site inhibitors. Including IPM elements like resistant cultivars are also seen as important steps to minimize the need for treatments, which again can help holding down the resistance levels.

Scientists, advisory services and chemical companies should help raising the awareness of the current situation and in communicating the recommendations to the farmers.

Data included on the platform originate from a phd project investigating sensitivity in the Nordic-Baltic region and from Eurowheat trials carried out in 2015.

References

• Wieczorek, TM, Roma Semaskine, Gunilla Berg, Andreas Mehl, Helge Sierotzkie, Gerd Stammlerf Annemarie Fejer Justesen, Lise Nistrup Jørgensen (2015)  Impact of azoles and SDHI fungicides on disease control and CYP51 mutations in the population of Zymoseptoria tritici in winter wheat. European Journal of Plant Pathology, Volume 143, Issue 4, pp 861-871.
• Cools, H. J. and B. A. Fraaije (2013). "Update on mechanisms of azole resistance in Mycosphaerella graminicola and implications for future control." Pest Management Science 69(2): 150-155.
• Leroux, P. and A. S. Walker (2011). "Multiple mechanisms account for resistance to sterol 14 alpha-demethylation inhibitors in field isolates of Mycosphaerella graminicola." Pest Management Science 67(1): 44-59.
• Stammler, G., M. Carstensen, A. Koch, M. Semar, D. Strobel and S. Schlehuber (2008). "Frequency of different CYP51-haplotypes of Mycosphaerella graminicola and their impact on epoxiconazole-sensitivity and -field efficacy." Crop Protection 27(11): 1448-1456.