Abstract
In 2003, a glyphosate-resistant plantago (Plantago lanceolata L.) population located in the Robertson district of South Africa was subjected to different glyphosate dosages and the highest dosage (7200 g a.e. ha−1) gave no acceptable levels of control. Here we reconfirm resistance and investigate the mechanism of glyphosate resistance. Dose-response curves indicated that the glyphosate dosage rate causing 50% survival (LD50) for the resistant (R) biotype is 43 times greater than for the susceptible (S) biotype, i.e., 43-fold resistant to glyphosate. Investigation into the molecular mechanism of plantago showed shikimate accumulation of the R biotype was lower than that of the S biotype. The reported 31P and 13C nuclear magnetic resonance (NMR) spectra show rapid glyphosate translocation into the young untreated leaves of the S biotype. No glyphosate translocation was observed in the R biotype. A point mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, resulting in an amino acid substitution was also observed, indicating two unique glyphosate resistance mechanisms within the R biotype. The rapid evolution of glyphosate-resistant weeds threatens the usage of the world’s most important herbicide (glyphosate), which is essential in world food production and further limits grower options for weed control. New weed management strategies will be necessary to combat plantago R biotypes.
Highlights
IntroductionGlyphosate resistant weed species have become very common and they threaten glyphosate-based weed management strategies
The results unambiguously show the first evidence of glyphosate resistance mechanisms in plantago
Glyphosate resistance in this R biotype is due to a Proline to Serine substitution at amino acid position 106 of the enolpyruvylshikimate3-phosphate synthase (EPSPS) gene, and reduced glyphosate translocation to young leaves
Summary
Glyphosate resistant weed species have become very common and they threaten glyphosate-based weed management strategies. This is because glyphosate is the world’s most important herbicide, and is used worldwide to control a broad spectrum of weeds in various cropping systems. Glyphosate resistance was first reported in 1996 in an apple orchard. Weeds can be destructive in various situations, the ones that have a major economic impact are those in glyphosate-resistant crops. Glyphosate is widely used to control weeds that are already resistant to other herbicides. Glyphosate resistant weeds pose a serious threat to sustainable weed management in agronomic crops
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