Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 17, 2013
Publication Date: May 29, 2013
Citation: Molin, W.T., Wright, A.A., Nandula, V.K. 2013. Glyphosate-resistant goosegrass from Mississippi. Agronomy. 3:474-487. Interpretive Summary: Glyphosate resistant goosegrass, an important weed found on Mississippi farms, was discovered and characterized to determine the level of resistance and the genetic mutation that caused the increase in resistance. This research was performed at the Crop Production Systems Research Unit in Stoneville Mississippi. The results show that the level of resistance in goosegrass was two to four times higher than in the sensitive goosegrass and was caused by a mutation in the target site gene. This greater tolerance to glyphosate will require farmers to use increased diligence to prevent the spread of this weed and could raise weed control costs in Mississippi production systems.
Technical Abstract: A glyphosate resistant population of goosegrass (Eleusine indica (L.) Gaertn.) was documented near Stoneville, Mississippi, USA, in an area which had received multiple applications of glyphosate each year for the previous eleven years. Resistance ratios based on dose response growth reduction assays were 2.1 to 4.6-times that of sensitive goosegrass. Resistance ratios based on a glyphosate sensitive shikimate accumulation bioassay were 5- to 8-times greater than the sensitive goosegrass. Sequence comparisons of epsps, the gene encoding the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), from the resistant biotype revealed a cytosine to thymine nucleotide change at position 319 (C319T) of the messenger RNA. This single nucleotide polymorphism (SNP) resulted in a proline to serine substitution at amino acid 106 (P106S). A genotyping assay was developed to detect the C319T SNP using real-time PCR technology. Screening of 42 goosegrass accessions from nearby farms and parks as well as from neighboring states indicated that the resistant biotype remained localized to the site where it was discovered.