The Resistance Levels and Target-Site Based Resistance Mechanisms to Glyphosate in Eleusine indica from China

Abstract

The Dongting and Poyang Lakes are the important rice growing areas, and the Bohai Rim and Loess Plateau are the main producing areas of apples in China, where glyphosate has been used continuously to control weeds including Eleusine. indica for many years. In this study, the resistance levels and target-site based resistance (TSR) mechanisms to glyphosate in E. indica populations, which were collected from above areas were investigated. A total of 35 out of 50 (70%) E. indica populations have evolved resistance to glyphosate with resistance index (RI) of 2.01~10.43. The glyphosate-resistant (GR) E. indica accumulated less shikimic acid than glyphosate-susceptible (GS) populations, when treated by 1.0 mg/L, 10 mg/L or 100 mg/L glyphosate. There was no mutation at Thr102 and Pro106 in 5-enolpyruvate shikimate-3-phosphate synthase (EPSPS), which endowed glyphosate resistance in E. indica and other weed species. A Pro-381-Leu was found in EPSPS in GR populations. In contrast, the expression level of EPSPS gene was highly correlated with glyphosate resistance in E. indica with a determination coefficient of 0.88. These indicate that the glyphosate resistance in aforementioned E. indica populations was mainly caused by the overexpression of EPSPS, not by amino acid mutation in EPSPS.