Glyphosate Resistance in Amaranthus viridis in Brazilian Citrus Orchards

Ricardo Alcántara- de la Cruz, Gabriel da Silva Amaral, Guilherme Moraes de Oliveira, Luiz Renato Rufino, Fernando Alves de Azevedo, Leonardo Bianco de Carvalho and Maria Fátima das Graças Fernandes da Silva
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Ricardo Alcántara- de la Cruz: Departamento de Química, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Gabriel da Silva Amaral: Departamento de Química, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Guilherme Moraes de Oliveira: Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Luiz Renato Rufino: Centro de Ciências Agrárias, Universidade Federal de São Carlos—Campus Araras, Araras 13604-900, Brazil
Fernando Alves de Azevedo: Centro de Citricultura “Sylvio Moreira”, Instituto Agronômico de Campinas (IAC), Cordeirópolis 13490-970, Brazil
Leonardo Bianco de Carvalho: School of Agricultural and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal 14884-900, Brazil
Maria Fátima das Graças Fernandes da Silva: Departamento de Química, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil

Agriculture, 2020, vol. 10, issue 7, 1-10

Abstract: Glyphosate is the main tool for weed management in Brazilian citrus orchards, where weeds, such as Conyza bonariensis and Digitaria insularis , have been found with resistance to this herbicide. Field prospections have allowed the identification of a possible new case of glyphosate resistance. In this work, the susceptibility levels to glyphosate on three Amaranthus viridis L. populations, with suspected resistance (R1, R2, and R-IAC), collected in citrus orchards from the São Paulo State, Brazil, as well as their accumulation rates of shikimic acid, were determined. The fresh weight of the susceptible population (S) was reduced by 50% (GR 50 ) with ~30 g ea ha −1 glyphosate, while the GR 50 values of the R populations were between 5.4 and 11.3 times higher than that for S population. The LD 50 (herbicide dose to kill 50% of individuals of a weed population) values of the S population were ≤150 g ea ha −1 glyphosate, while the LD 50 of the R populations ranged from 600 to 920 g ea ha −1 . Based on the reduction of fresh weight and the survival rate, the R1 population showed the highest level of glyphosate resistance, which had GR 50 and LD 50 values of 248 and 918 g ea ha −1 glyphosate, respectively. The S population accumulated 240 µg shikimic acid at 1000 µM glyphosate, while the R1, R2, and R-IAC populations accumulated only 16, 43, and 33 µg shikimic acid, respectively (between 5.6 to 15 times less than the S population). Enzyme activity assays suggested that at least one target site-type mechanism was involved in resistance. This result revealed the first report of glyphosate resistance in A. viridis reported in the world.

Keywords: dose-response; enzyme activity; herbicide resistance; shikimic acid; slender amaranth (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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