Rapid Assay Evaluation of Plant Response to Protoporphyrinogen Oxidase (Protox)-Inhibiting Herbicides

Abstract

Protoporphyrinogen oxidase (protox)-inhibiting herbicides damage cell membranes, resulting in electrolyte leakage. A whole-plant dose-response study and a rapid assay that measured electrolyte leakage was used to determine the response of wild mustard, soybean, and protox inhibitor–susceptible and protox inhibitor–resistant common waterhemp to increasing doses of three protox inhibitors: acifluorfen, fomesafen, and sulfentrazone. For the dose-response study, whole plants were treated with the three protox-inhibitor herbicides. Electroconductivity assay 1 consisted of cutting discs from leaf tissue and submerging them in an incubation medium containing concentrations of acifluorfen, fomesafen, or sulfentrazone. In electroconductivity assay 2, the entire leaf was treated with solutions containing acifluorfen, fomesafen, or sulfentrazone. The whole-plant dose-response study showed increasing visible injury with increasing herbicide rates for all species and all herbicides. The order of visible injury was wild mustard > susceptible common waterhemp > resistant common waterhemp > soybean. In assay 1, electrolyte leakage from leaf discs treated with acifluorfen or fomesafen increased with increasing herbicide concentrations, and was similar for all species. In contrast, electrolyte leakage from leaf discs treated with sulfentrazone did not increase with increasing herbicide concentrations for any species. In assay 2, only wild mustard leaf discs increased in electrolyte leakage with increasing herbicide rates of acifluorfen, fomesafen, and sulfentrazone and followed the regression curves established by the whole-plant dose-response study. However, assay 2 was not able to distinguish between susceptible wild mustard and tolerant soybean, or between susceptible and resistant waterhemp.

Annual Bluegrass (Poa annua) Biotypes Exhibit Differential Levels of Susceptibility and Biochemical Responses to Protoporphyrinogen Oxidase Inhibitors

“…Flessner et al (2013) reported that flumioxazin at 0.4 kg ha −1 controlled P. annua ≥95% up to a 2-tiller growth stage, but applications to plants with 4 to 6 tillers provided <50% control. Falk et al (2006) reported acifluorfen and fomesafen at 420 g ai ha −1 controlled a PPO-resistant biotype of A. tuberculatus greater than 85% at the 2-leaf and 4- to 6-leaf growth stage. However, applications to R-biotype plants at the 8- to 10-leaf growth stage ranged from 54% to 75%.…”

“…In Experiment 5, the differential levels of electrolyte leakage in the R- and S-biotypes were evaluated using a modified methodology from experiments described by Falk et al (2006). Electrolyte leakage is indicative of cellular membrane damage and can be used to describe the response levels to PPO inhibitors.…”

Electrolyte Leakage and the Protective Effect of Nitric Oxide on Leaves of Flooded Rice Exposed to Herbicides

“…After the last reading, the tubes were incubated for two hours in water bath, at 75 ± 2 o C, to obtain maximum conductivity -procedure adopted in all the experiments. The conductivity data was transformed into maximum conductivity percentage (Falk et al, 2006), and they were expressed in maximum potential conductivity (%) (Dayan et al, 1997). The concentrations and the incubation periods, in a factorial design, consisted of treatments organized under an entirely randomized design with four replications.…”

“…Therefore, it is a representation of the injury caused by oxidative stress in the membranes (Falk et al, 2006) and it has been used to assess the potential damage of herbicides such as protox inhibitors (Falk et al, 2006;Trezzi et al, 2011, Glomski;Netherland, 2013), photosynthetic electron transport inhibitors and carotenoid synthesis inhibitors (Kruse et al, 2006). In the crop of flooded rice, these herbicides come as an alternative for weed resistance management, and their selectivity, conditioned by several physiological and environmental factors, would be benefitted by the use of protectors.…”

Environmental and physiological factors that affect the efficacy of herbicides that inhibit the enzyme protoporphyrinogen oxidase: a literature review

“…flumioxazin, oxadiazon, oxyfluorfen, and sulfentrazone) or post-emergence of weeds (e.g. acifluorfen, fomesafen, lactofen, carfentrazone, flumiclorac, and fluthiacet) (Falk et al 2006, Senseman, 2007. To mitigate the problems of weeds resistant to glyphosate and other herbicides, PROTOXinhibitors tend to be used largely in agriculture worldwide.…”