The world's first glyphosate-resistant case of Avena fatua L. and Avena sterilis ssp. ludoviciana (Durieu) Gillet & Magne and alternative herbicide options for their control.

Bhagirath Singh Chauhan,Adnan Noor Shah

doi:10.1371/journal.pone.0262494

Abstract

Avena fatua and A. ludoviciana (commonly known as wild oats) are the most problematic winter grass species in fallows and winter crops in the northeast region of Australia. A series of experiments were conducted to evaluate the performance of glyphosate and alternative post-emergence herbicides on A. fatua and A. ludoviciana. This study reports the world’s first glyphosate-resistant (GR) biotypes of A. fatua and A. ludoviciana. The glyphosate dose required to kill 50% of the plants (LD50) and to reduce 50% of the biomass (GR50) for the GR biotype of A. fatua was 556 g a.e./ha and 351 g a.e./ha, respectively. These values for A. ludoviciana were 848 g a.e./ha and 289 g a.e./ha. Regardless of the growth stage (3–4 or 6–7 leaf stages), clethodim (120 g a.i./ha), haloxyfop (78 g a.i./ha), pinoxaden (20 g a.i./ha), and propaquizafop (30 g a.i./ha) were the best alternative herbicide options for the control of A. fatua and A. ludoviciana. The efficacy of butroxydim (45 g a.i./ha), clodinafop (120 g a.i./ha), imazamox + imazapyr (36 g a.i./ha), and paraquat (600 g a.i./ha) reduced at the advanced growth stage. Glufosinate (750 g a.i./ha), flamprop (225 g a.i./ha), and pyroxsulam + halauxifen (20 g a.i./ha) did not provide effective control of Avena species. This study identified alternative herbicide options to manage GR biotypes of A. fatua and A. ludoviciana.

Highlights

Weeds are an important biological constraint to the production of grains crops in Australia
Avena fatua L. and A. sterilis ssp. ludoviciana (Durieu) Gillet & Magne are the second most important grass weed in Australia, causing a revenue loss of more than AUD 28 million per annum to grain growers [1]
The LD50 and GR50 values of the GR biotype were only 1.2 to 1.5-fold greater than the GS biotype, the results confirmed evolution of glyphosate resistance has occurred in A. fatua

Summary

Introduction

Weeds are an important biological constraint to the production of grains crops in Australia. They cost Australian grain growers more than AUD 3.3 billion [1]. Avena fatua L. and A. sterilis ssp. Ludoviciana (Durieu) Gillet & Magne (hereafter, A. ludoviciana) (both known as wild oats in Australia) are the second most important grass weed in Australia, causing a revenue loss of more than AUD 28 million per annum to grain growers [1]. In the northeast grain region of Australia, Avena species are the top-ranked weed in terms of infested area (630,000 ha). A recent study reported that 15 to 16 plants/m2 of A. fatua and A. ludoviciana were enough to cause a 50% yield loss in wheat [2].

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