RESISTÊNCIA MÚLTIPLA DE Amaranthus Spp. A INIBIDORES DE EPSPS E ALS EM POPULAÇÕES COLETADAS EM REGIÕES DO ESTADO DE GOIÁS

Abstract

The increasing occurrence of herbicide-resistant weed populations has become one of the main challenges for agricultural production. In this context, species of the genus Amaranthus stand out due to their high adaptive capacity and the occurrence of biotypes resistant to different mechanisms of action. This study aimed to evaluate the sensitivity of Amaranthus spp. populations to glyphosate (EPSPS inhibitor) and chlorimuron (ALS inhibitor) using dose–response curve methodology. The experiments were conducted under greenhouse conditions, using nine populations collected from agricultural areas in the municipalities of Cristalina and Orizona, Goiás State, Brazil. Increasing herbicide doses were applied, and visual control (%) was assessed at 28 days after application, while relative dry mass (%) was used as a complementary variable. Data were fitted to a four parameter log-logistic model (LL.4), and the doses required to achieve 50% (ED₅₀) and 80% (ED₈₀) control were estimated. For the dry mass variable, growth reduction parameters were interpreted only for populations with satisfactory model fit, while for the others, a descriptive approach based on minimum and maximum observed values was adopted. The results revealed significant differences in sensitivity among the populations. For glyphosate, most populations showed resistance, particularly POP2, POP3, POP4, and POP5, whereas POP7 and POP9 were characterized as susceptible. For chlorimuron, resistance was even more pronounced, especially in POP8, POP1, and POP5, while POP7 showed higher susceptibility. The integrated analysis of ED₅₀, ED₈₀, and resistance factors (RF) confirmed the occurrence of resistant populations. These findings indicate the presence of multiple resistance to EPSPS and ALS inhibitors in Amaranthus spp. populations in Goiás State, Brazil, highlighting the need for integrated weed management strategies to mitigate resistance evolution.