Erigeron bonariensis L.: Caracterización de accesiones resistentes a glifosato en Colombia

Abstract

Effective weed management is essential in modern agriculture. Currently, glyphosate is the most used herbicide globally, offering non-selective and post-emergence weed control by inhibiting the EPSP synthase in chloroplasts. Ubiquitous and recurrent use of the same herbicidal mode of action may concurrently select herbicide-resistant biotypes and thus result in loss of efficacy. Hairy fleabane (Erigeron bonariensis L.) is a native South American species that has invaded many agroecosystems worldwide, commonly reported as a glyphosate-resistant weed. In Colombia, E. bonariensis is adapted to many ecological niches, including essential crop systems. Putative hairy fleabane resistance to glyphosate was purported since the late ’90s but eventually confirmed in Colombia’s coffee plantations in 2006. Consequently, anecdotal accounts by farmers suggest a prevalence of glyphosate-resistant fleabane in several crop systems in Colombia and consistent with the dispersion of glyphosate-resistance hairy fleabane reported for this species in other countries. Objective in this investigation was to detect the resistance to glyphosate, also to estimate the levels of that resistance and to propose effective chemical options to control E. bonariensis in Colombia. We conducted a resistance profile test under a greenhouse to evaluate ten hairy fleabane populations collected from different agricultural systems in Colombia. We confirmed that all populations were glyphosate-resistant, with at least 80% survival to the recommended field rate of 1080 g ae ha-1. Importantly, in 90% of populations, at least 80% of individuals survived to the double glyphosate field rate, suggesting high levels of glyphosate resistance in E. bonariensis from Colombia. As a reference, five pristine E. bonariensis populations collected from areas devoid of exposure to glyphosate were effectively controlled at the recommended rate, confirming that susceptibility still exists in non-sprayed areas. Characterization based on relative biomass through glasshouse dose-response studies identified one population with a low resistance factor (P10 with 3.15-fold) and a second, with a high resistance factor (P15 with 22.3-fold) when compared with the most sensitive population (P7), which had an ED50 of 109 g ae ha-1. Interestingly, both populations displayed hormesis at recommended glyphosate doses during this assessment. Finally, five herbicides with different modes of action were tested, identifying pyraflufen-ethyl as the most effective, followed by mesotrione; paraquat and glufosinate were the least effective. Our findings confirmed the prevalence of high glyphosate-resistant E. bonariensis in key crops throughout Colombia (i.e., plantain, banana, cassava, passionfruit, papaya, and red beans). Effective weed management strategies need to be implemented by Colombian farmers to mitigate the evolution of glyphosate resistance, combining mechanical and cultural control. Chemical alternatives include PPO and HPPD herbicides as part of the integrated weed management program.

El manejo efectivo de malezas es esencial en la agricultura moderna. Actualmente, glifosato es el herbicida más utilizado en el mundo, ofreciendo control efectivo de malezas, no-selectivo en post-emergencia al inhibir la enzima EPSP sintasa en los cloroplastos. El recurrente uso de un mismo modo de acción herbicida puede seleccionar biotipos resistentes al herbicida y resultar en la pérdida de eficacia. Erigeron bonariensis L. comúnmente llamada venadillo es una planta nativa de Sudamerica que ha invadido muchos ecosistemas en el mundo y que ha sido reportada como maleza resistente a glifosato en Colombia. E. bonariensis está adaptada a muchos nichos ecológicos, incluyendo agroecosistemas de cultivos esenciales. Se ha tenido sospecha de resistencia a glifosato en esta especie desde los años 90 y se confirmó resistencia desde 2006. El objetivo del presente estudio consistió en detectar la resistencia a glifosato en poblaciones de E. bonariensis en Colombia, estimar los niveles de resistencia y proponer medidas de control con herbicidas que fueran eficaces. En ensayos en invernadero, se confirmó que todas las poblaciones provenientes de agroecosistemas donde su había utilizado glifosato son resistentes a este herbicida, presentan porcentaje de supervivencia >80% a la dosis recomendada (1080 g ea ha-1). Además el 90% de las poblaciones sobrevivió un 80% de las plantas al usar el doble de esta dosis. En dos poblaciones caracterizadas los factores de resistencia fueron de 3,15 y 22,3 veces la dosis necesaria para controlar la población más sensible. Ésta población presentó un ED50 en base a biomasa de 109 g ea ha-1. Cinco herbicidas con diferente modo de acción fueron evaluados resultando pyraflufen-etyl y mesotrione los más efectivos y sugiriendo posibles casos resistencia múltiple con paraquat y a 2-4,D. (Texto tomado de la fuente).