Molecular Basis for Resistance to Fluazifop-P-Butyl in Itchgrass (Rottboellia cochinchinensis) from Costa Rica

Abstract

Rottboellia cochinchinensis is an annual grass weed species known as itchgrass, or "caminadora" in America´s Spanish speaking countries, and has become a major and troublesome weed in several crops. The application of fluazifop-P-butyl at recommended rates (125 g a.i. ha-1) was observed to be failing to control itchgrass in a field in San José, Upala county, Alajuela province, Costa Rica. Plants from the putative resistant R. cochinchinensis population survived fluazifop-P-butyl when treated with 250 g a.i. ha-1 (2X label rate) at the three- to four-leaf stage under greenhouse conditions. PCR amplification and sequencing of partial carboxyl transferase domain (CT) of the acetyl-CoA carboxylase (ACCase) gene were used to determine the molecular mechanism of resistance. A single non-synonymous point mutation from TGG (susceptible plants) to TGC (putative resistant plants) that leads to a Trp-2027-Cys substitution was found. This Trp-2027-Cys mutation is known to confer resistance to all aryloxyphenoxyproprionate (APP) herbicides to which fluazifop-P-butyl belongs. To the best of our knowledge, this is the first report of fluazifop-P-butyl resistance and a mutation at position 2027 for a Costa Rican R. cochinchinensis population.

Screening preemergence herbicides for weed control in cassava

“…Weed Technology site (Southern Guinea Savanna), Olorunmaiye and Olorunmaiye (2008) observed that coat buttons, crabgrass, and itchgrass were not controlled by S-metolachlor þ atrazine or by metolachlor þ metobromuron when applied PRE alone or when followed by one or two manual hoe-weedings at 6 and 12 WAP in a cassava/maize intercrop. Several studies have identified resistance in some populations of itchgrass to some acetyl coenzyme-A carboxylase-inhibiting herbicides in Bolivia and Costa Rica (Avila et al 2007;Castillo-Matamoros et al 2016). At the International Center for Tropical Agriculture in Colombia, oxyfluorfen did not control goosegrass at the label rate of 0.5 kg ai ha −1 (Tonggulum and Leihner 2015).…”

Detection of the Trp-2027-Cys Mutation in Fluazifop-P-butyl–resistant Itchgrass (Rottboellia cochinchinensis) using High-Resolution Melting Analysis (HRMA)

“…A pair of primers was designed using Primer3Plus program () based on a 292-bp CT domain of the ACCase gene sequence alignment from fluazifop-P-butyl–susceptible and fluazifop-P-butyl–resistant R. cochinchinensis plants (GenBank accession numbers: KM592092 and KM592093; Castillo-Matamoros et al 2016): RottF: 5′-GTTGACCCAGCCTGAAGAAT-3′ and RottR: 5′-GGATTGCCTCTGTTCATCCT-3′. Primers amplify an 89-bp fragment containing the target polymorphic site TG G (Trp)/TG C (Cys), codon 2027 (according to blackgrass [ Alopecurus myosuroides Huds.]…”

“…Over the last decade, acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides, which selectively inhibit the homomeric plastidic form of ACCase (EC.6.4.1.2) (Kaundun 2014), have been extensively used for managing R. cochinchinensis POST in a variety of crops (Avila et al 2007; Heap 2014, 2017). However, populations of R. cochinchinensis in Bolivia (Avila et al 2007), Costa Rica (Castillo-Matamoros et al 2016), and the United States (Heap 2017) have evolved resistance to ACCase inhibitors, including fluazifop-P-butyl, haloxyfop-R-methyl, fenoxaprop, and cyhalofop-butyl from the APP group, and clethodim and sethoxydim from the cyclohexanedione (CHDs/DIMs) chemistry. Resistance to these herbicides has made the management of this important weed more difficult and expensive.…”

Dry Heat and Exposure Time Influence Divine Nightshade and Itchgrass Seed Emergence

“…Repeated application of the same herbicide site of action to large weed numbers has resulted in the evolution of 255 herbicide-resistant weed species globally (Heap, 2019;Powles and Yu, 2010). Multiple resistance evolution to five herbicide sites of action have been reported in 19 weed species globally (Heap, 2019) (Avila et al, 2007;Castillo-Matamoros et al, 2016;Heap, 2019). Additional weed control strategies that complement herbicides are increasingly necessary because of the limited commercial release of new herbicide sites of action (Duke 2012).…”

“…No cases of divine nightshade evolving resistance to herbicides have been reported; however, few reports of itchgrass evolving resistance to herbicides have been documented globally. Failure to control itchgrass in soybean [ Glycine Max (L.)] with fluazifop‐P‐butyl has been documented in Louisiana, Bolivia, and Costa Rica, and itchgrass resistant to foramsulfuron, iodosulfuron‐methyl‐sodium, and nicosulfuron was reported in a Venezuelan corn [ Zea mays (L.)] field in 2004 (Avila et al, 2007; Castillo‐Matamoros et al, 2016; Heap, 2019). Additional weed control strategies that complement herbicides are increasingly necessary because of the limited commercial release of new herbicide sites of action (Duke 2012).…”