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Ex DC (ex + dc)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Three New Arylnaphthalide Lignans from the Aerial Parts of Bupleurum marginatumWall. ex DC.

HELVETICA CHIMICA ACTA, Issue 12 2008
Ying Liu
Abstract Three new arylnaphthalide lignans, 5-(4-hydroxy-3-methoxyphenyl)furo[3,,4,:,6,7]naphtho[2,3- d]-1,3-dioxol-6(8H)-one (1), 10-(4-hydroxy-3-methoxyphenyl)furo[3,,4,:,6,7]naphtho[1,2- d]-1,3-dioxol-9(7H)-one (2), and 10-(3,4-dimethoxyphenyl)-6-hydroxyfuro[3,,4,:,6,7]naphtho[1,2- d]-1,3-dioxol-9(7H)-one (3), together with two known ones, chinensin (4) and isodiphyllin (5), were isolated from the aerial parts of Bupleurum marginatumWall. ex DC. The structures of the three new lignans were established by means of NMR spectroscopic studies, including HQSC, HMBC, and ROESY. [source]

Weed species shifts in glyphosate-resistant crops

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2008
Micheal DK Owen
Abstract The adoption of glyphosate-based crop production systems has been one of the most important revolutions in the history of agriculture. Changes in weed communities owing to species that do not respond to current glyphosate-based management tactics are rapidly increasing. Clearly, glyphosate-resistant crops (GRCs) do not influence weeds any more than non-transgenic crops. For most crops, the trait itself is essentially benign in the environment. Rather, the weed control tactics imposed by growers create the ecological selection pressure that ultimately changes the weed communities. This is seen in the adoption of conservation tillage and weed management programs that focus on one herbicide mode of action and have hastened several important weed population shifts. Tillage (disturbance) is one of the primary factors that affect changes in weed communities. The intense selection pressure from herbicide use will result in the evolution of herbicide-resistant weed biotypes or shifts in the relative prominence of one weed species in the weed community. Changes in weed communities are inevitable and an intrinsic consequence of growing crops over time. The glyphosate-based weed management tactics used in GRCs impose the selection pressure that supports weed population shifts. Examples of weed population shifts in GRCs include common waterhemp [Amaranthus tuberculatus (Moq ex DC) JD Sauer], horseweed (Conyza canadensis L), giant ragweed (Ambrosia trifida L) and other relatively new weed problems. Growers have handled these weed population shifts with varying success depending on the crop. Copyright © 2008 Society of Chemical Industry [source]

Differential response of Amaranthus tuberculatus (Moq ex DC) JD Sauer to glyphosate

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2005
Ian A Zelaya
Abstract Midwest USA farmers have reported inconsistent control of Amaranthus tuberculatus (= rudis) (Moq ex DC) JD Sauer by glyphosate in glyphosate-resistant crops. The potential of selection for decreased A tuberculatus sensitivity to glyphosate was therefore investigated in a reportedly resistant Everly, IA population (P0,EV). Evaluation of six A tuberculatus populations from the Midwest USA estimated a seedling baseline sensitivity of 2.15 mM glyphosate. Based on these results, three generations of divergent recurrent selection were implemented on P0,EV to isolate resistant and susceptible populations. A seedling assay was developed to screen large amounts of seeds and thus expedite the selection process. Whole-plant and seedling rate responses of P0,EV and a known pristine A tuberculatus population from Paint Creek, OH (P0,WT) identified no significant difference in response to glyphosate; however, greater phenotypic variance was ostensibly evident in P0,EV. The first recurrent generation selected for resistance at 3.2 mM glyphosate (RS1,R) had a 5.9- and 1.7-fold resistance increase at the seedling and whole-plant levels, respectively, compared with the susceptible generation selected at 32 µM glyphosate. After three cycles of recurrent selection, 14.6-fold difference in resistance at the seedling level and 3.1-fold difference at the whole-plant level were observed when comparing the populations selected for resistance (RS3,R) and susceptibility (RS3,S). Overall, recurrent selection increased the frequency of resistant individuals and decreased the variability to glyphosate at the population level. Nevertheless, variability for glyphosate resistance was still evident in RS3,R. Results herein suggested that A tuberculatus is inherently variable to glyphosate and that selection decreased the sensitivity to glyphosate. We purport that evolved glyphosate resistance in A tuberculatus may require multiple cycles of selection under field conditions. Historic estimated use of glyphosate alludes to the evolution of tolerant weed populations. Copyright © 2005 Society of Chemical Industry [source]