Review: Confirmation of Resistance to Herbicides and Evaluation of Resistance Levels

• Published in: Weed science Vol. 61; no. 1; pp. 4 - 20
• Main Authors: Burgos, Nilda R., Tranel, Patrick J., Streibig, Jens C., Davis, Vince M., Shaner, Dale, Norsworthy, Jason K., Ritz, Christian
• Format: Journal Article
• Language: English
• Published: 810 East 10th Street, Lawrence, KS 66044-8897 Weed Science Society of America 01.01.2013; Cambridge University Press
• Subjects: Biological and medical sciences; Chemical control; Deoxyribonucleic acid; Design; DNA; dose response; Dose response relationship; Dose–response assay; Educational materials; Fundamental and applied biological sciences. Psychology; Genetic mutation; genomics; Global positioning systems; GPS; growers; Herbicide resistance; Herbicide resistant weeds; Herbicides; mechanism of action; Mode of action; molecular-based assay; Objectives; Parasitic plants. Weeds; Pest control; Phytopathology. Animal pests. Plant and forest protection; Plants; Polymerase chain reaction; Population; quick tests; resistance management; Resistance mechanisms; REVIEW; Sample size; sampling; Sampling methods; Scientists; screening; Seeds; Species; Studies; surveys; weed biology; Weeds; whole-plant assay; whole-plant assay; Dose–response assay; sampling; molecular-based assay; quick tests; Evaluation; Whole plant; Pesticides; Dose―response assay; Review; Herbicide; Dose activity relation; Assay; Resistance; Weed science; Sampling; Molecular domain
• ISSN: 0043-1745; 1550-2759
• DOI: 10.1614/WS-D-12-00032.1

As cases of resistance to herbicides escalate worldwide, there is increasing demand from growers to test for weed resistance and learn how to manage it. Scientists have developed resistance-testing protocols for numerous herbicides and weed species. Growers need immediate answers and scientists are faced with the daunting task of testing an increasingly large number of samples across a variety of species and herbicides. Quick tests have been, and continue to be, developed to address this need, although classical tests are still the norm. Newer methods involve molecular techniques. Whereas the classical whole-plant assay tests for resistance regardless of the mechanism, many quick tests are limited by specificity to an herbicide, mode of action, or mechanism of resistance. Advancing knowledge in weed biology and genomics allows for refinements in sampling and testing protocols. Thus, approaches in resistance testing continue to diversify, which can confound the less experienced. We aim to help weed science practitioners resolve questions pertaining to the testing of herbicide resistance, starting with field surveys and sampling methods, herbicide screening methods, data analysis, and, finally, interpretation. More specifically, this article discusses approaches for sampling plants for resistance confirmation assays, provides brief overviews on the biological and statistical basis for designing and analyzing dose–response tests, and discusses alternative procedures for rapid resistance confirmation, including molecular-based assays. Resistance confirmation procedures often need to be slightly modified to suit a specific situation; thus, the general requirements as well as pros and cons of quick assays and DNA-based assays are contrasted. Ultimately, weed resistance testing research, as well as resistance management decisions arising from research, needs to be practical, feasible, and grounded in science-based methods.