Reduced absorption of glyphosate and decreased translocation of dicamba contribute to poor control of kochia (<i>Kochia scoparia</i>) at high temperature

Pesticide efficacy is strongly associated with environmental conditions. Conditional resistance defined as a reduction in pesticide sensitivity under changed environmental conditions has been widely detected under climatic changes such as elevated temperatures and CO enrichment. Given the effects of environmental conditions on pesticide sensitivity, many of the putative resistance reports made by farmers may be due to pesticide application followed by non-optimal environmental conditions rather than the evolution of resistance. This type of conditional resistance may be the result of phenotypic plasticity or epigenetic changes in response to environmental changes. Elevated temperatures and CO enrichment can directly lead to reduced pesticide efficacy by altering pesticide metabolism and translocation, or indirectly increasing pesticide detoxification in host-plants thus reducing pesticide availability for the target pest. Stress-related signal transduction pathways, as well as physiological changes, can both be associated with accelerated pesticide detoxification under climatic changes. The possibility for parallel mechanisms controlling these responses in different pest species should be considered. It is proposed that the same mechanisms leading to non-target site resistance in pests may also play a role in conditional resistance, suggesting we can predict the pesticides to which pests are likely to be less responsive under changing climatic conditions. Using adjuvants to improve pesticide translocation or reduce pesticide metabolism, alongside with new technologies such as using nanoparticles may result in higher pesticide functionality under the projected climate change. Exploring the physiological, transcriptional and biochemical basis underlying conditional resistance is crucial in maintaining future pest management under changing environmental conditions. © 2018 Society of Chemical Industry.

Section: Conditional Resistancementioning

confidence: 78%

Climate change exacerbates pest damage through reduced pesticide efficacy

Matzrafi

2018

“…The absorption and translocation experiments were conducted according to previously described methods . The percent absorption and translocation of [ 14 C] dicamba were calculated using the following formulae: percent absorption = (R applied − R rinsate )/R applied × 100; percent translocation = 100 − R TL /(R applied − R rinsate ) × 100; percent ATL = R ATL /(R applied − R rinsate ) × 100; percent TL = R TL /(R applied − R rinsate ) × 100; and percent BTL = R BTL /(R applied − R rinsate ) × 100, where R applied is total amount of radioactivity applied on the plant; R rinsate is the radioactivity recovered in leaf rinsates; R ATL is the radioactivity recovered in tissue above the treated leaf; R TL is the radioactivity recovered in the treated leaf; and R BTL is the radioactivity recovered in tissue below the treated leaf.…”

Section: Methodsmentioning

confidence: 99%

Increased chalcone synthase (CHS) expression is associated with dicamba resistance in Kochia scoparia

Pettinga

Patterson

et al. 2017

Self Cite

Prior work has shown that the flavonols quertecin and kaemperfol compete with auxin for intercellular movement and vascular loading via ATP-binding cassette subfamily B (ABCB) membrane transporters. The results of this study support a model in which constitutively increased CHS expression in the meristem produces more flavonols that would compete with dicamba for intercellular transport by ABCB transporters, resulting in reduced dicamba translocation. © 2017 Society of Chemical Industry.

“…Modifications in plant structure (e.g. alteration in cuticle properties) may reduce herbicide absorption, limiting the amount of glyphosate that reaches the meristems, and has been reported to confer low glyphosate resistance in Kochia scoparia (L.) A. J. Scott . Reduced glyphosate translocation, shown in several weed species, may allow plants to survive to higher herbicide doses compared with target‐site resistance mechanisms .…”

Section: Introductionmentioning

confidence: 99%

“…alteration in cuticle properties) may reduce herbicide absorption, limiting the amount of glyphosate that reaches the meristems, and has been reported to confer low glyphosate resistance in Kochia scoparia (L.) A. J. Scott. 11 Reduced glyphosate translocation, shown in several weed species, may allow plants to survive to higher herbicide doses compared with target-site resistance mechanisms. 9 Experiments using nuclear magnetic resonance showed up to ten times more 31 P-glyphosate in the vacuole of the resistant biotype of Conyza canadensis (L.) Cronquist compared with the susceptible biotype, 9 likely mediated by ATP binding cassette (ABC) transporters in the tonoplast.…”

Section: Introductionmentioning

confidence: 99%

EPSPS duplication and mutation involved in glyphosate resistance in the allotetraploid weed species Poa annua L.

Brunharo

Morran

Martin

et al. 2019

BACKGROUND Poa annua is a widespread winter annual weed species in California. Recently, poor control of this species with glyphosate was reported by growers in an almond orchard in California with a history of repetitive glyphosate use. The objectives of this research were to evaluate the level of glyphosate resistance in a developed S4 P. annua line (R) and identify the mechanisms of resistance involved. RESULTS Whole‐plant dose–response experiments confirmed glyphosate resistance in R, which required 18‐fold more glyphosate to achieve a 50% growth reduction compared with a susceptible line (S), results that were supported by the lower shikimate accumulation observed in R compared with S. No differences in glyphosate absorption, translocation, or metabolism were observed, suggesting that non‐target‐site mechanisms of resistance are not involved in the resistance phenotype. A missense single nucleotide polymorphism was observed in EPSPS coding position 106 in R, resulting in a leucine to proline substitution. This polymorphism was observed exclusively in P. supina EPSPS homeologs. A seven‐fold increase in the number of copies of EPSPS alleles was observed in R compared with S. CONCLUSIONS We report the first case of glyphosate resistance associated with both EPSPS duplication and target‐site mutation at position 106, leading to high levels of glyphosate resistance in the allotetraploid weed species Poa annua L. Data obtained in this research will be useful for the development of diagnostic tools for rapid glyphosate resistance identification, monitoring and containment. © 2018 Society of Chemical Industry