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1 October 2006 A Seedling Assay to Screen Aryloxyphenoxypropionic Acid and Cyclohexanedione Resistance in Johnsongrass (Sorghum halepense)
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Abstract

A seedling bioassay was developed for the rapid diagnosis of resistance to clethodim and fluazifop-P in johnsongrass. The assay was based on differences in the coleoptile length of susceptible (S) and resistant (R) seedlings exposed to clethodim and fluazifop-P in petri dishes for 5 d. Bioassay concentrations of 0.09 mg/L clethodim and 0.18 mg/L fluazifop-P were chosen as discriminant based on rate responses of each biotype to increasing herbicide dose. At 5 d after treatment (DAT), the amounts of clethodim required to reduce coleoptile length by 50% (GR50) for the R and S seedlings were 462.5 and 24.8 mg/L, respectively, resulting in an R:S ratio of 18.7. The fluazifop GR50 values for the R and S seedlings were 618.7 and 17.5 mg/L, respectively, resulting in a R:S ratio of 35.4.

Nomenclature: Clethodim, fluazifop-P, johnsongrass, Sorghum halepense (L.) Pers. #3SORHA.

Additional index words: ACCase inhibitors, herbicide resistance.

Abbreviations: ACCase, acetyl coenzyme-A carboxylase; AOPP, aryloxyphenoxypropionate; CHD, cyclohexanedione.

Ian C. Burke, Walter E. Thomas, JAMES D. BURTON, JANET F. SPEARS, and John W. Wilcut "A Seedling Assay to Screen Aryloxyphenoxypropionic Acid and Cyclohexanedione Resistance in Johnsongrass (Sorghum halepense)," Weed Technology 20(4), 950-955, (1 October 2006). https://doi.org/10.1614/WT-05-160.1
Published: 1 October 2006
JOURNAL ARTICLE
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