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

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.

Molecular basis of resistance to bensulfuron-methyl and cross-resistance patterns to ALS-inhibiting herbicides in Ludwigia prostrata

“…The sequence analysis results indicated that the target-site ALS gene Pro-197-Ser mutation was mainly responsible for bensulfuronmethyl resistance in the JS-R L. prostrata biotype. High-level ALSinhibiting herbicide resistance conferred by the same Pro-197-Ser substitution has been reported in some resistant weed species, including D. sophia (Cui et al 2011;Deng et al 2015), rigid ryegrass (Lolium rigidum Gaudin) (Yu et al 2010), C. bursa-pastoris (Cui et al 2012;Zhang et al 2020), M. aquaticum (Liu et al 2015), wild radish (Raphanus raphanistrum L.) (Yu et al 2003), wild buckwheat (Polygonum convolvulus L.) (Pandian et al 2020), and B. syzigachne (Wang et al 2020). However, to our knowledge, this is the first report of the Pro-197-Ser resistance mutation identified in L. prostrata.…”

Evolution of Herbicide Resistant Weeds in Agro-ecological Systems

“…Resistance is defined as the inherited ability of a plant/weed to survive and reproduce following exposure to a herbicide dose that used to be lethal to the same weed species. For example, Senecio vulgaris (L.) was the first weed that showed resistance to triazine herbicides but to date, 511 unique cases of herbicide-resistant weed species have been reported globally [4,5]. These cases have increased by 14% (233 to 266) in the last 20 years.…”

Herbicide Resistance in Weed Management

“…Auxinic herbicides, 2,4-D, and mecoprop-P, were suggested as a potential alternative for the management of these resistant populations. Pandian et al [5] reported on the first case of TS resistance to ALS inhibitors in a Poly-gonum convolvulus population from KS, USA. McKenzie-Gopsill et al [6] described TS resistance of Chenopodium album to metribuzin, a photosystem II-inhibiting herbicide.…”