Glyphosate resistance in Eleusine indica (L.) Gaertn. from different origins and polymerase chain reaction amplification of specific alleles

Abstract

Glyphosate-resistant populations of Eleusine indica (L.) Gaertn. were found in 4 areas in Malaysia that had received repeated applications of glyphosate for a period ranging from 5 to 15 years. The resistance ratios calculated from dose-response experiments were 2.9 (Chaah), 2.1 (Lenggeng), 3.3 (Bidor), and 2.8 (Temerloh). Two-point mutations were detected in position 875 within the 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) gene resistant population, causing a C to T transition leading to Pro₁₀₆ to Ser₁₀₆ substitution in Bidor and Temerloh or C to A transversion leading to Pro₁₀₆ to Thr₁₀₆ substitution in Chaah. Sequence comparisons of the 3115 bp of the EPSPS gene revealed identical sequences in both the susceptible (S) and resistant (R) populations of Lenggeng. The identical sequences in both the Lenggeng populations, S and R, suggest that the resistance mechanism found in Lenggeng R may be different from Chaah R, Bidor R, and Temerloh R. The polymerase chain reaction (PCR) amplification of specific alleles (PASA) was developed to detect 2 distinct single-point mutations, probably conferring herbicide resistance in Chaah R, Bidor R, and Temerloh R. PASA profiles showed only one DNA fragment for the entire S population and 2 different additional fragments, each specific for one resistance allele, for the R population.