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

José G Vázquez-García,Rafael De Prado,Sajedeh Golmohammadzadeh,Antonia M Rojano-Delgado,José A Domínguez-Valenzuela,Candelario Palma-Bautista,Hugo E Cruz-Hipólito

doi:10.3390/agronomy10030377

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.

Highlights

Agricultural crops are exposed to environmental factors that influence their growth, development, and productivity [1]
C. distichophylla seeds were collected from areas of soybean cultivation in Rio Grande do Sul, Brazil, where the control of this weed was very poor after the application of glyphosate at a rate of 720 g ae ha−1 [7]
The appearance of a new resistant species such as C. distichophylla demonstrates the difficulty that farmers face due to a lack of knowledge and tools that are as effective as glyphosate available to combat the serious problem of resistance in Brazil

Summary

Introduction

Agricultural crops are exposed to environmental factors that influence their growth, development, and productivity [1]. The genus Chloris is poorly known and includes numerous weed species that are distributed across multiple continents in both tropical and subtropical regions. Many species of this genus are native to Argentina (C. elata and C. virgata), Brazil (C. elata and C. polydactyla), the Caribbean. [synonym: Eustachys distichophylla (Lag.) Nees], commonly known as false-star-grass or weeping fingergrass, is found in areas where soybean and fruit crops are grown in southern Brazil [7]. Losses in soybean productivity can reach a 70% decrease when the soybean competes with Chloris polydactila, confirming the need to control the species of the same genus [8].

Objectives

Methods

Results

Discussion

Conclusion