Shikimate accumulation, glyphosate absorption and translocation in horseweed biotypes

Abstract

-In Brazil, few research works on mechanisms of weed resistance to glyphosate have been conducted so far. Therefore, this research aimed to study analytical procedures determining the relation between the concentration of plant shikimate after glyphosate application and the plant resistance to this herbicide; and evaluate the glyphosate absorption and translocation into two resistant (R) and susceptible (S) horseweed biotypes to glyphosate. Horseweed plants with nine true leaves received glyphosate (720 g a.e. ha -1 ), and 2, 3, 4, 7 and 10 days after application (DAA) the concentration of shikimic acid was measured by HPLC. In another experiment, plants were treated with radiolabeled glyphosate ( 14 C) (1.456 MBq mmol -1 specific activity) and radioactivity was measured 4, 8, 24, 48 and 72 hours after treatment (HAT) by liquid scintillation spectrometry. The shikimate concentration in plants increased 16,351.14 and 7,892.25 mg kg -1 of dry weight, for R and S plants respectively, at seven DAA. Therefore, the procedure for quantification of shikimic acid was suitable for R and S plants differentiation to glyphosate, indicating that the R population is actually resistant to glyphosate. On average, 98% of glyphosate applied was absorbed by the studied biotypes, at 72 HAT. Around 68% of the absorbed radioactivity remained on the biotypes leaves treated, the S biotype showing the highest translocation. Therefore, the R biotype resistance mechanism studied is associated to the differential translocation.Keywords: Conyza bonariensis, High Performance Liquid Chromatography, EPSPS, selection, radioactivity. CARDINALI, V.C.B. et al. RESUMO -No

Phosphate Status Affects Phosphate Transporter Expression and Glyphosate Uptake and Transport in Grand Eucalyptus (Eucalyptus grandis)

“…Rootward glyphosate translocation was greater in P− plants over the first 48 h (P<0.01), while P+ plants showed similar glyphosate distributions in roots and leaves (Figure 4C). The plateau observed at 72 h is consistent with studies that showed the majority of glyphosate is absorbed by 72 h (Cardinali et al 2015). Autoradiography showed that the glyphosate translocation was consistent with these quantifications (Figure 4D).…”

Reduced translocation is involved in resistance to glyphosate and paraquat in Conyza bonariensis and Conyza canadensis from California

“…Removal of non‐absorbed herbicide was compared among five solvents previously reported in the literature: distilled water (Perez et al ., ); 0.1% (v/v) Triton X‐100 (Wakelin et al ., ), methanol 75% (v/v) (Cardinali et al ., ), methanol 10% (v/v) plus 0.25% (v/v) non‐ionic surfactant (NIS) (Brunharo et al ., ), and acetone 50% (v/v) (Michitte et al ., ). All solvents were diluted in distilled water.…”

Glyphosate Resistance Affect the Physiological Quality of Conyza bonariensis seeds

“…The mechanism of glyphosate resistance in Conyza spp. is not related to the herbicide target enzyme (5-enolpyruvylshikimate 3-phosphate synthase, EPSPS), but to other molecular, physiological, biochemical, and morphological changes (Peng et al, 2010;Cardinali et al, 2015;Moretti et al, 2017;Hereward et al, 2018;Piasecki et al, 2019b). However, changes that occur in plants due to the resistance process may result in fitness costs for resistant plants in relation to sensitive plants (Yuan et al, 2007;Délye, 2013).…”