Target site as the main mechanism of resistance to imazamox in a Euphorbia heterophylla biotype

• Autor(a) principal: Rojano-Blanco, Antonia
• Data de Publicação: 2019
• Outros Autores: Portugal, João, Palma-Bautista, Candelario, Alcantara-de la Cruz, Ricardo, Torra, Joel, Alcantara, Esteban, De Prado, Rafael
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/20.500.12207/5424
• topic: Euphorbia heterophylla; Pest control; Extensive crop areas; Imazamox; Controlo de infestantes; Herbicida

Euphorbia heterophylla is a weed species that invades extensive crop areas in subtropical regions of Brazil. This species was previously controlled by imazamox, but the continuous use of this herbicide has selected for resistant biotypes. Two biotypes of E. heterophylla from southern Brazil, one resistant (R) and one susceptible (S) to imazamox, were compared. The resistance of the R biotype was confrmed by dose-response assays since it required 1250.2g ai ha−1 to reduce the fresh weight by 50% versus 7.4g ai ha−1 for the S biotype. The acetolactate synthase (ALS) enzyme activity was studied using ALS-inhibiting herbicides from fve diferent chemical families. The R biotype required the highest concentrations to reduce this enzyme activity by 50%. A Ser653Asn mutation was found in the ALS gene of the R biotype. The experiments carried out showed that imazamox absorption and metabolism were not involved in resistance. However, greater 14C-imazamox root exudation was found in the R biotype (~70% of the total absorbed imazamox). Target site mutation in the ALS gene is the principal mechanism that explains the imazamox resistance of the R biotype, but root exudation seems to also contribute to the resistance of this biotype