title: Phytotoxicity assay for seed production using Brassica rapa L.
abstract: Although pesticide drift can affect crop yield adversely, current plant testing protocols emphasize only the potential impacts on vegetative plant growth. The present study was conducted to determine whether a plant species with a short life cycle, such as Brassica rapa L. Wisconsin Fast Plants®, can be used to indicate potential effects on seed production of herbicides applied at relatively low levels (e.g., low field application rates [FAR]). The effects of ≤0.1 × FAR of aminopyralid, cloransulam, glyphosate, primisulfuron, or sulfometuron applied 14 d after emergence (DAE), were evaluated for B. rapa grown in mineral soil in pots under greenhouse conditions. Effects were expressed as the effective concentration of the herbicide producing a 25% reduction in a response (EC25) based on nonlinear regression. Brassica rapa seed dry weight was reduced by sulfometuron at an EC25 of 0.00014 × a field application rate (FAR) of 53 g active ingredient (a.i.) ha(-1), primisulfuron at 0.008 (experiment 1) or 0.0050 (experiment 2) × FAR of 40 g a.i. ha(-1), cloransulam at 0.022 × FAR of 18 g a.i. ha(-1), glyphosate at 0.0399 × FAR of 834 g a.i. ha(-1), and by aminopyralid at 0.005 × FAR of 123 g a.i. ha(-1), but only for 1 of 2 experiments. Reduced seed production occurred at less than the FAR that reduced shoot dry weight with sulfometuron and primisulfuron, whereas neither aminopyralid, cloransulam, nor glyphosate affected shoot dry weight. A short life cycle form of B. rapa could be used to indicate reduced seed production with plants grown only 1 week longer (∼35 DAE) than as the current vegetative vigor test for nontarget herbicide effects on plants.
authors.affiliation: US Environmental Protection Agency, Corvallis, Oregon 97333, USA. olszyk.david@epa.gov
authors.forename: David
authors.initials: D
authors.lastname: Olszyk
authors.forename: Thomas
authors.initials: T
authors.lastname: Pfleeger
authors.forename: E Henry
authors.initials: EH
authors.lastname: Lee
authors.forename: Milton
authors.initials: M
authors.lastname: Plocher
mesh_terms: D029741:Brassica rapa / Q000187:drug effects* / Q000254:growth & development* / Q000502:physiology; D004784:Environmental Monitoring / Q000379:methods*; D006540:Herbicides / Q000009:adverse effects*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D054817:Pollination / Q000187:drug effects; D012639:Seeds / Q000187:drug effects* / Q000254:growth & development*; D013997:Time Factors; D018675:Toxicity Tests / Q000379:methods*
chemical_list: D006540:Herbicides