Confirmation and Characterization of the First Case of Acetolactate Synthase (ALS)-Inhibitor—Resistant Wild Buckwheat (Polygonum convolvulus L.) in the United States

 by Balaji Aravindhan Pandian¹,Abigail Friesen¹,Martin Laforest²,Dallas E. Peterson¹,P. V. Vara Prasad^1,3 and Mithila Jugula¹,

1 Department of Agronomy, Kansas State University, Manhattan, KS 66506, USA

2 Research and Development Centre, Agriculture and Agri-Food Canada (AAFC), Saint-Jean-sur-Richelieu, QC J3B 3E6, Canada

3 Sustainable Intensification Innovation Lab, Kansas State University, Manhattan, KS 66506, USA

*Author to whom correspondence should be addressed. Agronomy 2020, 10(10), 1496;

https://doi.org/10.3390/agronomy10101496

Abstract

Wild buckwheat (Polygonum convolvulus L.) is a problem weed and ALS-inhibitors (e.g., chlorsulfuron) are commonly used for its management. Recently, a population of wild buckwheat (KSW-R) uncontrolled with ALS-inhibitors was found in a wheat field in Kansas, USA. The objectives of this research were to determine the level and mechanism of resistance to chlorsulfuron and cross resistance to other ALS-inhibitors in the KSW-R population. In response to chlorsulfuron rates ranging from 0 to 16x (x = 18 g ai/ha), the KSW-R wild buckwheat was found >100-fold more resistant compared to a known ALS-inhibitor susceptible (KSW-S) wild buckwheat. Also, >90% of KSW-R plants survived field recommended rates of sulfonylurea but not imidazolinone family of ALS-inhibitors. A portion of the ALS gene covering all previously reported mutations known to bestow resistance to ALS-inhibitors was sequenced from both KSW-R and KSW-S plants. The Pro-197-Ser substitution that confers resistance to the sulfonylurea herbicides was found in KSW-R plants. Our results support the evolution of high level of chlorsulfuron resistance as a result of a mutation in the ALS-gene in KSW-R buckwheat. This is the first case of resistance to any herbicides in wild buckwheat in the US.