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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR AND GENETIC MECHANISMS OF FUNGAL DISEASE RESISTANCE IN GRAIN CROPS Title: The dodge of blotch: Saving sex in Mycosphaerella graminicola

Authors
item Kema, Ghj -
item Ware, Sb -
item Van Der Lee, Taj -
item Wittenberg, Ahj -
item Diaz, C -
item Goodwin, Stephen
item DE Waard, MA -
item M"barek, S Ben -

Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: February 5, 2010
Publication Date: March 30, 2010
Citation: Kema, G., Ware, S., Van Der Lee, T., Wittenberg, A., Diaz, C., Goodwin, S.B., De Waard, M., M"Barek, S. 2010. The dodge of blotch: Saving sex in Mycosphaerella graminicola. Meeting Proceedings.

Technical Abstract: Mycosphaerella graminicola is the causal agent of septoria tritici blotch, currently the most important disease of wheat in Europe. Despite the recent identification of 15 resistance genes, disease control is currently achieved mainly by fungicides. However, fungicide resistance develops rapidly in natural M. graminicola populations. To understand the rapid spread of resistance we performed crossing experiments which demonstrate that external stress factors hamper disease development but cannot prevent sexual development. The first stress factor was host resistance. Various crosses indicated that sex always takes place as long as one of the mating partners is virulent. Thus, even an avirulent isolate that does not establish a compatible interaction with the host plant is perfectly able to enter into the sexual process resulting in viable ascospores. We used strobilurin fungicides as a second stress factor by crossing sensitive and resistant isolates under various strobilurin concentrations (3-200%). Although strobilurins prevent disease development of sensitive isolates, and as a consequence minimize biomass, abundant sexual development occurred under all conditions, thus irrespective of the applied strobilurin concentration. Moreover, our results showed that the ‘stressed’ mating partner acted as the preferred paternal partner. A minimal dose of 6% strobilurin already rendered entire populations resistant to these compounds. This explains the rapid pan-European spread of strobilurin resistance in M. graminicola, likely in temporally and geographically independent occasions, with no loss of nuclear genetic variation. The recently discovered genome plasticity of M. graminicola may contribute to its ability to overcome environmentally adverse conditions.

Last Modified: 12/24/2014
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