Herbicide-Resistant Crops: Utilities and Limitations for Herbicide-Resistant Weed Management

Since 1996, genetically modified herbicide-resistant (HR) crops, particularly glyphosate-resistant (GR) crops, have transformed the tactics that corn, soybean, and cotton growers use to manage weeds. The use of GR crops continues to grow, but weeds are adapting to the common practice of using only glyphosate to control weeds. Growers using only a single mode of action to manage weeds need to change to a more diverse array of herbicidal, mechanical, and cultural practices to maintain the effectiveness of glyphosate. Unfortunately, the introduction of GR crops and the high initial efficacy of glyphosate often lead to a decline in the use of other herbicide options and less investment by industry to discover new herbicide active ingredients. With some exceptions, most growers can still manage their weed problems with currently available selective and HR crop-enabled herbicides. However, current crop management systems are in jeopardy given the pace at which weed populations are evolving glyphosate resistance. New HR crop technologies will expand the utility of currently available herbicides and enable new interim solutions for growers to manage HR weeds, but will not replace the long-term need to diversify weed management tactics and discover herbicides with new modes of action. This paper reviews the strengths and weaknesses of anticipated weed management options and the best management practices that growers need to implement in HR crops to maximize the long-term benefits of current technologies and reduce weed shifts to difficult-to-control and HR weeds

Analysis, cloning, and high-level expression of 2,4-dichlorophenoxyacetate monooxygenase gene tfdA of Alcaligenes eutrophus JMP134.

Plasmid pJP4 of Alcaligenes eutrophus JMP134 contains all genes for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). Five of these genes, tfdB, tfdC, tfdD, tfdE, and tfdF, have recently been localized and cloned (R. H. Don, A. J. Weightman, H.-J. Knackmuss, and K. N. Timmis, J. Bacteriol. 161:85-90, 1985). Gene tfdA, which codes for the 2,4-D monooxygenase, has now been found by mutagenesis with transposon Tn5. A 3-kilobase fragment of pJP4 cloned in a broad-host-range vector could complement the 2,4-D-negative phenotype of two mutants which lacked 2,4-D monooxygenase activity. The cloned tfdA gene was also transferred to A. eutrophus JMP222, which is a cured derivative of JMP134. The recombinant strain could utilize phenoxyacetic acid as a sole source of carbon and energy. Pseudomonas sp. strain B13, containing the cloned tfdA, was able to degrade phenoxyacetic acid and 4-chlorophenoxyacetic acid. Gene tfdA was subcloned and analyzed by deletions. Expression of 2,4-D monooxygenase in Escherichia coli containing a 1.4-kilobase subfragment was demonstrated by radioisotopic enzyme assay, and a protein of 32,000-dalton molecular mass was detected by labeling experiments. A 2-kilobase subfragment containing tfdA has been sequenced. Sequence analysis revealed an open reading frame of 861 bases which was identified as the coding region of tfdA by insertion mutagenesis

Capabilities for Physical Activity by Turkish- and Russian-Speaking Immigrants Aged 65 Years and Older in Germany: A Qualitative Study

This study builds upon Sen’s seminal capability approach to analyze the interplay of individual and structural factors for immigrants’ physical activity (PA) in old age. The authors conducted software-assisted thematic analysis of group interviews with Turkish- and Russian-speaking immigrants aged 65 years and older in Germany (n = 19). The authors present how interviewees perceive diverse resources, environmental, social, and individual factors that shape their capabilities for PA. Age-related health literacy, family support, and access rules to sport opportunities shape both groups’ capabilities for PA. Turkish interviewees’ continuous bilocation and Russian interviewees’ past experience with PA as workplace exercise are two major differences between those groups. Results indicate that capabilities are ambiguous—managed and shaped by individuals, which makes more static terms like barriers and options less helpful for an analysis. Systematically applying the capability approach in intervention research would allow to analyze interaction and to ultimately better reach underserved groups like immigrants 65 years and older.</jats:p

Purification and properties of an Arthrobacter oxydans P52 carbamate hydrolase specific for the herbicide phenmedipham and nucleotide sequence of the corresponding gene.

Arthrobacter oxydans P52 isolated from soil samples was found to degrade the phenylcarbamate herbicides phenmedipham and desmedipham cometabolically by hydrolyzing their central carbamate linkages. The phenylcarbamate hydrolase (phenmedipham hydrolase) responsible for the degradative reaction was purified to homogeneity. The enzyme was shown to be a monomer with a molecular weight of 55,000. A 41-kb wild-type plasmid (pHP52) was identified in A. oxydans P52, but not in a derivative of this strain that had spontaneously lost the ability to hydrolyze phenylcarbamates, indicating that the gene for phenylcarbamate degradation (pcd) is plasmid encoded. Determination of two partial amino acid sequences allowed the localization of the coding sequence of the pcd gene on a 3.3-kb PstI restriction fragment within pHP52 DNA by hybridization with synthetic oligonucleotides. The phenylcarbamate hydrolase was functionally expressed in Escherichia coli under control of the lacZ promoter after the 3.3-kb PstI fragment was subcloned into the vector pUC19. A stretch of 1,864 bases within the cloned Pst fragment was sequenced. Sequence analysis revealed an open reading frame of 1,479 bases containing the amino acid partial sequences determined for the purified enzyme. Sequence comparisons revealed significant homology between the pcd gene product and the amino acid sequences of esterases of eukaryotic origin. Subsequently, it was demonstrated that the esterase substrate p-nitrophenylbutyrate is hydrolyzed by phenmedipham hydrolase