Multiple-and Cross-Resistance of Amaranthus retroflexus to Acetolactate Synthase (ALS) and Photosystem II (PSII) Inhibiting Herbicides in Preemergence

A Francischini,H.K Takano,J Constantin,R.S Oliveira Jr,R.R Mendes

doi:10.1590/s0100-83582019370100026

A Francischini, H.K Takano + Show 3 more

Open Access

https://doi.org/10.1590/s0100-83582019370100026

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Abstract

ABSTRACT: Herbicide resistance in Amaranthus genus occurs frequently around the word and has become a big problem in cotton producing areas. The objective of this work was to evaluate cross-and multiple-resistance of redroot pigweed (A. retroflexus) to herbicides used in preemergence in cotton fields in Brazil. Seven dose-response experiments were conducted with herbicides atrazine, prometryn, diuron, S-metolachlor, trifluralin, trifloxysulfuron-sodium and pyrithiobac-sodium, and the treatments consisted of application rates of 0, ¼, ½, 1, 2 and 4 times the recommended label rate. Eight A. retroflexus byotipes with suspect of resistance were sampled for experiments in three brazilian states of cotton producing. Resistance to prometryn was confirmed for one biotype in Goiás (GO), and one biotype from Mato Grosso (MT) showed cross-resistance to atrazine and prometryn. One byotipe from GO was identified with cross-resistance to trifloxysulfuron-sodium and pyrithiobac-sodium. One of the GO samples was identified with multiple resistance to prometryn and ALS inhibitors, another one to atrazine and ALS inhibitors, while MT byotipe was confirmed with multiple resistance to triazines and pyrithiobac. The herbicides S-metolachlor, diuron, and trifluralin were efficient for control of this species, therefore, they can be used as managment alternative in those regions.

Highlights

In Brazil, the average number of confirmed cases of herbicide resistance is two per year
The mechanism of action that present the greatest number of cases are acetolactate synthase inhibitors (ALS) and photosystem II inhibitors (PS II)
The objective of this research was to evaluate the occurrence of cross resistance to ALS-and PS II-inhibiting herbicides in redroot pigweed (A. retroflexus) biotypes, studied by Francischini et al (2014b), but this time with preemergence applications of products used in cotton fields

Summary

Introduction

In Brazil, the average number of confirmed cases of herbicide resistance is two per year. Forty-three cases have been recorded to date, which places Brazil in the fifth position in the ranking of countries with the greatest number of resistance reports, behind the United States, Australia, Canada and France (Heap, 2019). The use of herbicides with these two mechanisms of action is frequent (ALS inhibitor and PS II inhibitor), e.g., trifloxysulfuron-sodium, pyrithiobac-sodium, atrazine, prometryn and diuron. These herbicides are recommended for several mono- and dicotyledonous weed control, besides having crop selectivity in applications over the entire area or by spraying it over inter-rows (Rodrigues and Almeida, 2011)

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