Resistance to Propanil in Ricefield Bulrush (Schoenoplectus mucronatus) Is Conferred by apsbAMutation, Val₂₁₉to Ile

Abstract

Determining the mechanisms of herbicide resistance in weeds allows for the development and implementation of applied management practices aimed to control and to prevent further spread of herbicide-resistant populations in crop fields. This research was conducted to determine propanil resistance and cross-resistance to other photosystem II (PSII) inhibitors in ricefield bulrush biotypes and to elucidate the mechanism of propanil resistance. To this end, propanil-resistant (R) and propanil-susceptible (S) biotypes were selected from field-collected populations after propanil spraying at the field rate, and whole-plant, dose–response experiments were conducted to evaluate cross-resistance to PSII inhibitors and interactions between propanil and the insecticides malathion and carbaryl. In addition, thepsbAgene from R and S biotypes was sequenced for amino acid alterations following polymerase chain reaction (PCR) amplification. Plant survival data indicated the R biotype displayed a 14-fold increase in propanil resistance relative to the susceptible (S) biotype. In addition, the propanil-R biotype also had increased resistance to the PSII-inhibitors bromoxynil, diuron, and metribuzin but was more susceptible to bentazon than were propanil-S plants. Synergism between propanil and the insecticides carbaryl and malathion was greater in the S biotype than it was in the R biotype, indicating that, unlike propanil resistance in weedy grasses, enhanced degradation of the herbicide molecule is not a mechanism of resistance for propanil in ricefield bulrush. A Val219to Ile substitution in the propanil-R chloroplast D1 protein was identified following sequencing of thepsbAgene. This research suggests a single-point mutation at the target site causes resistance to propanil, diuron, metribuzin, and bromoxynil but increasing susceptibility to bentazon in propanil-R ricefield bulrush, a novel Val219–Ile feature. To our knowledge, this is the first instance of propanil resistance in weeds because of a mechanism other than enhanced herbicide metabolism. Tank-mixing bentazon and propanil, where permitted, can control both propanil-R and propanil-S biotypes.

A novel psbA mutation (Phe274–Val) confers resistance to PSII herbicides in wild radish (Raphanus raphanistrum)

“…For example, although providing resistance to metribuzin and diuron, the Val219-Ile mutation confers super-sensitivity to bromoxynil in Kochia scoparia 39 and bentazon (a benzothiazinone PSII herbicide) in Schoenoplectus mucronatus and Cyperus difformis. 40,41 In our results, wild radish plants with the Ser264-Gly mutation (population 264-Gly) showed super-sensitivity to bromoxynil, compared with the S plants. In addition to population 264-Gly, plants containing the Ser264-Gly mutation from three other wild radish populations were also tested for bromoxynil sensitivity.…”

“…Super‐sensitivity has been frequently observed for a number of resistance‐endowing psbA mutations in bacteria and green algae and plants. For example, although providing resistance to metribuzin and diuron, the Val219–Ile mutation confers super‐sensitivity to bromoxynil in Kochia scoparia and bentazon (a benzothiazinone PSII herbicide) in Schoenoplectus mucronatus and Cyperus difformis . In our results, wild radish plants with the Ser264–Gly mutation (population 264‐Gly) showed super‐sensitivity to bromoxynil, compared with the S plants.…”

Modo de Acción y Resistencia de los Herbicidas que Interfieren en el Fotosistema II de la Fotosíntesis

“…Los biotipos resistentes metabolizan el propanil más rápido y en mayor proporción que los susceptibles ya que la enzima aril acilamidasa tiene mayor actividad de (Leah et al 1995). Además, una mutación de valina por isoleucina en la posición 219 le ha dado resistencia a la maleza Schoenoplectus mucronatus (Pedroso et al 2016).…”

“…Casi todos los herbicidas que afectan la fotosíntesis son móviles, se absorben por la raíz y son translocados por el xilema hacia las hojas cuando ocurre la transpiración (Pedroso et al 2016). Cuando son aplicados a las hojas actúan como herbicidas de contacto y no se mueven de las hojas (Stephenson y Ries 1967).…”

“…Herbicidas móviles, se translocan en la planta. Son absorbidos por las raíces y las hojas (Pedroso et al 2016); cuando se aplican al suelo se mueven por el xilema hacia las hojas, aplicados al follaje permanecen en las hojas. Los grupos con este modo de acción son las triazinas, triazinonas, las fenil ureas, los uracilos, piridazinonas y fenil-carbonatos.…”