New Case of False-Star-Grass (Chloris distichophylla) Population Evolving Glyphosate Resistance

Abstract

Chloris distichophylla, suspected of glyphosate resistance (GR), was collected from areas of soybean cultivation in Rio Grande do Sul, Brazil. A comparison was made with a susceptible population (GS) to evaluate the resistance level, mechanisms involved, and control alternatives. Glyphosate doses required to reduce the dry weight (GR50) or cause a mortality rate of 50% (LD50) were around 5.1–3 times greater in the GR population than in the GS population. The shikimic acid accumulation was around 6.2-fold greater in GS plants than in GR plants. No metabolized glyphosate was found in either GR or GS plants. Both populations did not differ in the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) basal activity or in vitro inhibition of EPSPS activity by glyphosate (I50). The maximum glyphosate absorption was observed at 96 hours after treatment (HAT), which was twofold higher in the GS plants than in the GR plants. This confirms the first case of glyphosate resistance in C. distichophylla. In addition, at 96 HAT, the GS plants translocated more 14C-glyphosate than the GR ones. The best options for the chemical control of both C. distichophylla populations were clethodim, quizalofop, paraquat, glufosinate, tembotrione, diuron, and atrazine. The first case of glyphosate resistance in C. distichophylla was due to impaired uptake and translocation. Chemical control using multiple herbicides with different modes of action (MOA) could be a tool used for integrated weed management (IWM) programs.

Resistance Evolution to EPSPS Inhibiting Herbicides in False Barley (Hordeum murinum) Harvested in Southern Spain

“…[23,24], Chloris spp. [25][26][27][28], Echinochloa colona [29][30][31], Digitaria insularis [32], and Sorghum halepense [33][34][35]. The only case of glyphosate resistance in the genus Hordeum was detected in Australia in 2016 in the subspecies H. murinum subsp.…”

“…glaucum [13], in other grass weed species, both target-site and non-target-site resistance mechanisms can evolve. Reduced absorption, retention, impaired transport, metabolism, point mutations, and amplification of the EPSPS gene have been cited [23][24][25][26][27][28][29][30][31][32][33][34][35].…”

First Case of Glyphosate Resistance in Bromus catharticus Vahl.: Examination of Endowing Resistance Mechanisms

“…Since the herbicide affects actively growing tissues, the demand for assimilates would decrease and consequently induce an accumulation of carbohydrates in the leaves associated with a feedback inhibition of CO 2 fixation, but as the light stage of photosynthesis is initially unaffected, a redirection of electrons to alternative electron sinks occurs, conducive to oxidative stress, that ultimately leads to plant death ( Yanniccari et al, 2012a , b ). As a consequence, a restricted translocation of glyphosate has been frequently detected as an important mechanism of resistance in several weed species ( Feng et al, 2004 ; Wakelin et al, 2004 ; Koger and Reddy, 2005 ; Vila-Aiub et al, 2012 ; Ghanizadeh et al, 2016 ; Dominguez-Valenzuela et al, 2017 ; Vázquez-García et al, 2020a , b ). Going further, a process of glyphosate sequestration within the cell vacuole was detected as a basis of glyphosate altered translocation in resistant Conyza canadensis and Lolium spp.…”

“…14 C-glyphosate (glycine-2- 14 C) plus commercial glyphosate solution was applied to R and S B. catharticus plants following the methods described by Vázquez-García et al (2020a , b) and carried out at University of Córdoba (Spain). Plants were treated at the 3–4-leaf stage and there were five repetitions and each experiment was arranged in a completely randomized design.…”

Levantamento fitossociológico das plantas daninhas em diferentes frutíferas de clima temperado no Município de Lavras – MG

“…Chloris é um gênero ainda pouco conhecido, contudo este inclui numerosas especies de plantas daninhas, as quais, são distribuídas nas regiões tropicais e subtropicais. C. radiata (L.) Sw é originária da Argentina e como as demais espécies é de alta competitividade e dificil controle através dos herbicidas (Vázquez-García et al, 2020). O glifosato é utilizado no controle das espécies do gênero Chloris, mas estas apresentam resistência, devido as diversas aplicações sem intercalamento com um controle alternativo (Powles, 2008).…”