SOURGRASS (Digitaria insularis) with GROUP G/9 resistance: (INHIBITION OF ENOLPYRUVYL SHIKIMATE PHOSPHATE SYNTHASE ) Inhibition of EPSP synthase
MUTATION: PROLINE 106 to THREONINE
Sourgrass (Digitaria insularis) is a monocot plant in the poaceae family. A single amino acid substitution from Proline 106 to Threonine has led to resistance to Inhibition of Enolpyruvyl Shikimate Phosphate Synthase as indicated in the table below.		Sourgrass

Chemical Family	Example Herbicide	Resistance Level
Glycines	glyphosate	Intermediate Resistance < 10 fold

REFERENCES

Carvalho, L. B. de ; Alves, P. L. da C. A. ; González-Torralva, F. ; Cruz-Hipolito, H. E. ; Rojano-Delgado, A. M. ; Prado, R. de ; Gil-Humanes, J. ; Barro, F. ; Luque de Castro, M. D.. 2012. Pool of resistance mechanisms to glyphosate in Digitaria insularis. Journal of Agricultural and Food Chemistry 60 : 615 - 622.

Digitaria insularis biotypes resistant to glyphosate have been detected in Brazil. Studies were carried out in controlled conditions to determine the role of absorption, translocation, metabolism, and gene mutation as mechanisms of glyphosate resistance in D. insularis. The susceptible biotype absorbed at least 12% more ¹⁴C-glyphosate up to 48 h after treatment (HAT) than resistant biotypes. High differential ¹⁴C-glyphosate translocation was observed at 12 HAT, so that >70% of the absorbed herbicide remained in the treated leaf in resistant biotypes, whereas 42% remained in the susceptible biotype at 96 HAT. Glyphosate was degraded to aminomethylphosphonic acid (AMPA), glyoxylate, and sarcosine by >90% in resistant biotypes, whereas a small amount of herbicide (up to 11%) was degraded by the susceptible biotype up to 168 HAT. Two amino acid changes were found at positions 182 and 310 in EPSPS, consisting of a proline to threonine and a tyrosine to cysteine substitution, respectively, in resistant biotypes. Therefore, absorption, translocation, metabolism, and gene mutation play an important role in the D. insularis glyphosate resistance..

This case was entered by Todd Gaines Email: todd.gaines@colostate.edu

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