EASTERN BLACK NIGHTSHADE (Solanum ptycanthum) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: ALANINE 122 to THREONINE
Eastern Black Nightshade (Solanum ptycanthum) is a dicot plant in the solanaceae family. A single amino acid substitution from Alanine 122 to Threonine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Eastern Black Nightshade

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Resistant > 10 fold
Pyrimidinyl benzoates	Bispyribac-Na	Not Determined
Sulfonylureas	Chlorsulfuron	Susceptible
Triazolopyrimidine - Type 1	Chloransulam-methyl	Not Determined
Triazolinones	Flucarbazone-Na	Not Determined

NOTE

REFERENCES

Milliman, L. D. ; Riechers, D. E. ; Wax, L. M. ; Simmons, F. W.. 2003. Characterization of two biotypes of imidazolinone-resistant eastern black nightshade (Solanum ptycanthum). Weed Science 51 : 139 - 144.

Biotypes of eastern black nightshade (S. ptycanthum) that were not controlled by postemergence applications of imazethapyr were found in Illinois and Indiana, USA. Greenhouse studies were conducted to determine whole-plant responses to the imidazolinone herbicides imazethapyr and imazamox and to the sulfonylurea herbicide primisulfuron-methyl [primisulfuron]. The Illinois and Indiana resistant biotypes were highly resistant to imazamox and imazethapyr but were not cross-resistant to primisulfuron-methyl. DNA sequencing of acetolactate synthase (ALS) genes showed that the molecular basis for resistance in both resistant biotypes was a single base-pair mutation within Domain C that changed an alanine to a threonine in their encoded enzymes. In vitro enzyme assays showed that the Illinois resistant biotype's ALS enzyme was 789- and 881-fold less sensitive than that of the susceptible biotype to imazamox and imazethapyr, respectively. The Indiana resistant biotype's ALS enzyme was 110- and 158-fold less sensitive than that of the susceptible biotype to imazamox and imazethapyr, respectively. These results are consistent with the amino acid substitution found in the ALS enzyme of both resistant biotypes of eastern black nightshade..

Milliman, L. D., D.E. Riechers, F. W. Simmons, And L. M. Wax. 2000. Two biotypes of eastern black nightshade that are resistant to ALS-inhibiting herbicides. Proceedings of the North Central Weed Science Society 55 : 86.

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This case was entered by Patrick Tranel Email: tranel@illinois.edu

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