Julius-Kühn-Archiv (Feb 2014)
Spatial and temporal development of ACCase and ALS resistant Black-grass (Alopecurus myosuroides Huds.) populations in neighboring fields in Germany
Abstract
The repetitive use of herbicides of a given mode of action as primary tools to control weeds in simplified cropping systems has led to the development of resistant populations. This study reports preliminary results of the infestation level and the herbicide resistance structure of blackgrass (Alopecurus myosuroides Huds.) in circa 40 neighboring fields in each of three locations in Southern Germany during 2010-2012. In each location one field with confirmed field resistance served as a starting point to survey the surrounding fields. Field infestation was assessed at the end of the season where seeds were harvested. Based on greenhouse biotests nearly all tested fields showed resistance to ACCase, but the pattern of ACCase mutations and metabolic resistance to fenoxaprop-ethyl showed differences according to space and time. High resistance to ALS was found in several fields in two locations where ALS-resistance was previously confirmed in a single field only leading to severe crop failure. Interestingly, either Pro197 or Trp574 seemed to dominate in these two locations, while almost no ALS target-site mutations were found in the third location. Target-site mutations appear to be the major mechanism for these early cases of ALS-resistance. A few fields also showed non-target site resistant plants to mesosulfuron-methyl. This unique data set provides new insights into the structure and development of 1) an established resistance (ACCase-inhibitors) and 2) a developing resistance (ALS-inhibitors). Multivariate analysis including greenhouse biotests data and target-site analyses corresponding to mutations conferring resistance showed that even spatially closely related fields develop different herbicide resistance patterns. This suggests that weed control measures have a major impact within each field and that resistance can evolve independently. In the current situation black-grass infestations can still be controlled in most of the fields. Integrated Weed Management tools can contribute to keep the selection pressure low and slow down resistance development.
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