First report of glyphosate and paraquat resistance in two Plantago biotypes

Abstract

Resistance to glyphosate in plantago (Plantago lanceolata L.), a serious weed in South Africa, was confirmed in 2003. More recently, a plantago biotype that is putatively resistant to both glyphosate and paraquat was reported. Seeds from a putatively susceptible (S) plantago population and from two putatively resistant populations (R1 and R2) were subjected to glyphosate and paraquat. To investigate possible multiple resistance, sequential application of glyphosate and paraquat was explored. The results showed an LD50 of 891.89 g a.e. ha−1 and 387.75 g a.i. ha−1 for glyphosate and paraquat respectively for the S biotype. For glyphosate, the LD50 value for R1 was 3842.61 g a.e. ha−1. The LD50 for the R2 biotype to glyphosate was 2020.39 g a.e. ha−1. The paraquat LD50 values for the R1 and R2 biotypes were 785.14 and 1246.43 g a.i. ha−1 respectively, resulting in resistance indices of 2 and 3 respectively. Sequential application of glyphosate and paraquat was not effective in plantago management. The R biotypes showed resistance to both glyphosate and paraquat indicating possible multiple resistance.