Modulation of Physiological Stress Response of Triticum aestivum L. to Glyphosate by Brassinosteroid Application.

Elena Shopova,Neveen B Talaat,Zornitsa Katerova,Ljudmila Dimitrova,Iskren Sergiev,Liliana Brankova,Dessislava Todorova

doi:10.3390/life11111156

Abstract

The potential of brassinosteroids to modulate the physiological responses of winter wheat (Triticum aestivum L.) to herbicide stress was evaluated. Young winter wheat seedlings were treated with 24-epibrassinolide (EBL) and 24 h later were sprayed with glyphosate. The physiological responses of treated plants were assessed 14 days after herbicide application. Wheat growth was noticeably inhibited by glyphosate. The herbicide application significantly increased the content of the stress markers proline and malondialdehyde (MDA) evidencing oxidative damage. The content of phenolic compounds was decreased in the herbicide-treated plants. Slight activation of superoxide dismutase (SOD) and catalase (CAT) and considerable increase of glutathione reductase (GR) and guaiacol peroxidase (POX) activities were found. Increased POX and glutathione S-transferase (GST) activities were anticipated to be involved in herbicide detoxification. Conjugation with glutathione in herbicide-treated plants could explain the reduction of thiols suggesting unbalanced redox state. EBL application did not alter the plant growth but a moderate activation of antioxidant defense (POX, GR, and CAT activities and phenolic levels) and detoxifying enzyme GST was observed. The hormonal priming provoked a slight decrease in MDA and proline levels. The results demonstrate that EBL-pretreatment partly restored shoot growth and has a potential to mitigate the oxidative damages in glyphosate-treated plants through activation of the enzymatic antioxidant defense and increase of the phenolic compounds.

Highlights

Herbicides are often used in modern agricultural practice to manage weed growth
The present study aims to expand the knowledge of the potential of EBL pretreatment to mitigate negative effects from foliar glyphosate application on wheat through assessment of growth parameters, stress markers and non-enzymatic and enzymatic antioxidant system
We confirmed that glyphosate treatment reduces substantially wheat growth and inhibits the non−enzymatic defense of the affected plants

Summary

Introduction

Glyphosate (N-(phosphonomethyl)glycine) use has increased 15-fold from 1994 to 2014 on a worldwide scale [1]. It is the most extensively used herbicide, weed resistance to its usage has emerged. The introduction of glyphosate-resistant crops in agricultural practice caused an additional rise in the use of the herbicide in soybean, corn, cotton, and wheat cultivation [3,9]. Glyphosate is a broad-spectrum, non-selective herbicide, killing all affected plants. It inhibits the plastidic 5-enolpyruvylshikimate-3 phosphate synthase, a key enzyme in the shikimate pathway. The plants treated with this herbicide exhibited stunted growth and impaired photosynthesis [5,10,17]

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Conclusion