Identifying the Mechanism of Resistance to the ALS-Inhibiiting Herbicide Metsulfuron in Spotted Spurge (Euphorbia maculata (L.)).

Herbicide resistance is a growing issue in agriculture. With herbicide sales in the billions, companies want to know if plants are, in fact, becoming resistant to certain herbicides. Spotted spurge (Euphorbia maculata (L.)) has been identified as resistant to the herbicide metsulfuron in Georgia.  Spurge is common in seashore paspalum and Metsulfuron is one of the few herbicides registered for weed control in this turfgrass. Metsulfuron inhibits acetolactate synthase (ALS), a key enzyme in branched chain amino acid formation.  Greater than 100 weed biotypes have evolved resistance in the world.  The majority of resistance cases are due to a target-site resistance mechanism.  Target-site resistance is a mutation in the coding region of the target protein leading to an amino acid substitution which in turn reduces binding affinity of the herbicide to the protein. The research question we have proposed is aimed at deducing possible target-site resistance mutations causing resistance by sequencing the ALS gene. Knowledge of the exact mutation will inform management decisions as certain mutations can cause cross-resistance to herbicides related to metsulfuron. The first step in understanding the mutation is to extract the RNA, followed by cDNA conversion, from spotted spurge of known resistance and susceptibility to metsulfuron.  The polymerase chain reaction will be conducted to amplify the ALS gene segments followed by capillary sequencing of these segments.  Upon careful comparison of each individual nucleotide with respect to the two populations, we will identify possible mutation sites (missense, nonsense, etc.).