Capim pé-de-galinha (Eleusine indica) resistente ao glyphosate no Brasil

Abstract

After the beginning of the Roundup Ready crops commercialization, the use of glyphosate has increased substantially. This led to the selection of up to seven glyphosate resistant weed species. In addition, goosegrass control failures have been observed in annual crops fields of the Western Paraná State. In this sense, the objectives of this dissertation were: a) to evaluate the growth, development and seed production of this species; b) to confirm glyphosate resistance in goosegrass from Brazil; c) to identify the mechanism of glyphosate resistance in this species; d) to validade a molecular marker for rapid detection of glyphosate resistant goosegrass populations; e) to evaluate alternative herbicides for glyphosate resistant goosegrass control. Initially, a biology study was carried out evaluating the growth, development and seed production of goosegrass. Dose-response experiments of glyphosate were also carried out with goosegrass populations collected in areas where plant survival after glyphosate application was observed. Subsequently, the mechanism of resistance was investigated through a shikimate accumulation assay in plants after glyphosate application. We also sequenced a 330-bp fragment of the EPSPS gene. In addition, a TaqMan probe was designed based on a SNP (Single Nucleotide Polimorphism) in the EPSPS gene responsible for glyphosate resistance in goosegrass. Finally, several pre and post-emergence herbicides were evaluated for controlling glyphosate resistant goosegrass. The results showed that the beginning of tillering occurs as early as 9 days after emergence (DAE) and at 38 DAE the plant initiates the exponential growth phase and seed production, which increases its capacity for competition and dissemination of propagules. Resistance to glyphosate was confirmed in at least two goosegrass populations. The shikimate accumulation in susceptible plants was up to seven times greater than in resistant plants after glyphosate application. The mechanism of resistance is associated with an amino acid mutation from a proline to a serine at 106 position (P106S). The TaqMan® probe has been validated for rapid detection of resistance, presenting reproducibility and precision. The use of residual herbicides for glyphosate-resistant goosegrass control constitutes a very important tool for effective management. The application timing is crucial for post-emergence efficacy.