Location: Crop Production Systems Research
Project Number: 6066-21000-060-000-D
Project Type: In-House Appropriated
Start Date: Oct 26, 2015
End Date: Oct 25, 2020
Objective 1: Discover, identify and characterize physiological, biochemical and molecular mechanisms of resistance in herbicide-resistant weeds. Sub-objective 1A. Document distribution, nature, and level of resistance to herbicides, including cross resistance and multiple resistance, in weed populations of MS and Southeastern U.S. Sub-objective 1B. Determine the physiological/biochemical/molecular mechanisms of resistance to herbicides in weed populations where the level and nature of resistance is known. Sub-objective 1C. Determine the nature of metabolism-based non-target site herbicide (ALS inhibitors, propanil, quinclorac) resistance in Echinochloa spp. Objective 2: Determine the effects of herbicide resistance (especially for Amaranthus weeds) on plant fitness and growth characteristics (e.g., photosynthetic capacities, seed bank size and longevity, competitiveness, and stress responses) as compared to corresponding herbicide-sensitive biotypes. Sub-objective 2A. Evaluate the competitiveness of GR-hybrids of A. spinosus and A. palmeri, glyphosate-sensitive A. spinosus and GR-A. palmeri in soybean. Sub-objective 2B. Evaluate the persistence and level of glyphosate resistance in hybrids following glyphosate application. Objective 3: Characterize the extent of hybridization among Amaranthus weed species, and determine how hybridization impacts the spread of herbicide-resistance in this genus. Sub-objective 3A. In greenhouse crosses, evaluate the inheritance of resistance by examining fertility, morphological traits, and changes in copy number of EPSPS in F1 hybrids with and without glyphosate. Sub-objective 3B. Determine the viability of pollen and seeds from hybrids. Sub-objective 3C. Perform in situ hybridization to determine the distribution of the EPSPS amplicon among chromosomes. Sub-objective 3D. Determine if the size and contents of the EPSPS amplicon are consistent across populations from different locations. Objective 4: Discover biological and cultural weed control methods that can be integrated with herbicides and other chemicals to manage herbicide-resistant weeds. Sub-objective 4A. Determine the efficacy of field crop rotations on glyphosate-resistant pigweed populations. Sub-objective 4B. Determine efficacy of new 2,4-D and dicamba formulations alone and in combination with 1 or more additional herbicide modes of action on glyphosate- and acetolactate synthase inhibitor-resistant broadleaf weeds. Sub-objective 4C. Determine possible multiple herbicide resistance in horseweed, Palmer amaranth and other populations of weed species using bioassays with multiple herbicides. Sub-objective 4D. Determine compatibility and possible synergistic interaction of bioherbicidal pathogens (MV, X. campestris isolate LVA987, and others) with herbicides (2,4-D, dicamba and other auxinic herbicides, glyphosate, etc.) to be used on new multiple-herbicide resistant crops.
The overall project goal is to discover basic and practical knowledge of the occurrence, distribution, mechanism of resistance and management of weeds that are resistant to single or multiple herbicides. This holistic approach will generate more effective weed control and management practices. The development of weed management tools, aided by knowledge of resistance mechanisms and weed biology will foster the development of novel, sustainable practices for early detection and management of resistant weeds. Basic growth analyses, assays and bioassays using whole plants and plant tissues from laboratory, greenhouse and field experiments will determine major changes in resistant versus susceptible biotypes. Subsequent biochemical, genetic, proteomic, immunochemical and radiological studies will identify and characterize specific site differences in herbicide resistant and sensitive weed biotypes within species. The knowledge generated will provide a greater understanding of the biochemistry, physiology and genetics of resistance mechanisms and provide insight for recommendations to promote efficacious and sustainable weed control coupled with more efficient and economic crop production.