Genetic diversity and in silico evidence of target-site mutation in the EPSPS gene in endowing glyphosate resistance in Eleusine indica (L.) from Malaysia

Glyphosate-resistant populations of Eleusine indica are widespread in several states of Malaysia. A whole-plant bioassay confirmed that eight out of the 17 populations tested were resistant to glyphosate at double the recommended rate of 2.44 kg ha-1. Screening with allele-specific PCR (AS-PCR) revealed that resistant plants contained an EPSPS gene with either the homozygous S/S-106 or the heterozygous P/S-106 alleles. All susceptible plants contained only the homozygous P/P-106 allele. In addition, DNA sequences of the full-length EPSPS gene from one susceptible (SB) and four resistant (R2, R6, R8 and R11) populations revealed an amino acid substitution of T102I in all the resistant plants, while another substitution of P381L was only found in resistant populations R6 and R11. The significance of the P381L mutation was examined by Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) and residue interaction network (RIN) analyses, which suggests the P381L mutation may contribute to resistance. Mutations at 102 and 106 occur widely in the EPSPS gene of glyphosate-resistant E. indica populations from Malaysia with the TIPS mutation. In addition, the P381L mutation could also contribute to resistance.