Location: Crop Production Systems Research2019 Annual Report
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.
Studies on the determination of metabolites of multiple herbicides in a metabolic resistant biotype of junglerice from Mississippi are in progress. International collaboration, with scientists from the United Kingdom and Japan, is being initiated for molecular characterization of metabolic resistance in junglerice from Mississippi. Absorption and metabolism of dicamba in dicamba-resistant soybean is currently being investigated. Characterization of resistance mechanisms in multiple herbicide resistant Phalaris minor is in progress. Investigation of dicamba tolerance in selected non-dicamba-resistant soybean germplasm is currently underway. Glyphosate-susceptible and -resistant Palmer amaranth populations with varying levels of betalin and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) copy numbers are being examined for differential traits of secondary plant metabolism. Hemp sesbania plants treated with hot water (45°C - 95°C), followed by applications of fungal spores of a bioherbicide (Colletotrichum truncatum) were controlled 85% in the greenhouse and field, respectively, 12 days after treatment. Results suggest that hot water may be an important tool for improving the infectivity and bioherbicidal potential of some plant pathogens. Characterization of a multiple resistant (glyphosate, PPO, ALS) Palmer amaranth accession from Mississippi is proceeding. Investigation of glyphosate metabolism in resistant Russian thistle is ongoing. Spores of the bioherbicide Colletotrichum gloeosporioides f. sp. aeschynomene formulated in a surfactant controlled three weed species (northern jointvetch, Indian jointvetch, and hemp sesbania) in greenhouse experiments. Results suggest that the host range of CGA can be expanded though formulation modification enabling this bioherbicide to control multiple weeds. Horseweed seedlings exposed to drought/desiccation survived less than 48 hours. The small seed (1 mm x 0.3 mm) has little survival capacity in the absence of continuous hydration, thus even though a single plant may produce 200,000 seed, its abundance and proliferation are limited under dry environments. Acetyl-coenzyme A carboxylase inhibitor resistance studies of Italian ryegrass populations from North Carolina were completed and a paper was submitted for publication. A non-technical summary was published describing how Palmer amaranth went from a weed relatively easy to control to a major herbicide resistant weed problem and assesses how agronomic practices influenced the rise and extent of the glyphosate-resistant Palmer amaranth problem. Additional plants (Amaranthus spp.) from Mississippi were identified through screening field populations for possible PPO resistance and are being crossed with traditional glyphosate and ALS resistant pigweed to determine the extent of resistance transfer. The 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) replicon in glyphosate-resistant Palmer amaranth was shown to be attached to chromosomes by tethering genes. These genes are being explored as targets for ribonucleic acid interference (RNAi) to inhibit binding.
1. Influence of water quality, formulation, adjuvant, rainfastness, and spray nozzle type on efficacy of fomesafen on Palmer amaranth (Amaranthus palmeri) control. The use of protoporphyrinogen oxidase (PPO) inhibitors is one of the few remaining post-emergence herbicide options for controlling Palmer amaranth in soybean in areas of Mississippi. Greenhouse studies conducted by ARS researchers in Stoneville, Mississippi, evaluated factors affecting the efficacy of fomesafen, a PPO inhibitor, on Palmer amaranth including: quality of spray carrier (water), formulations, adjuvant, rainfastness, and nozzle type. Water quality, formulation, adjuvant, rainfastness, or nozzle type did not affect the activity of fomesafen under optimal application conditions in the greenhouse. These research results are important since these application parameters can be modified to prolong the sustainability of PPO inhibitors as well as slow the spread of resistance to PPO inhibitors such as fomesafen, which is clearly the preferred treatment in glyphosate-resistant soybean.
2. Glyphosate-resistant junglerice (Echinochloa colona) from Mississippi and Tennessee: confirmation and resistance mechanisms. Recently, several incidents of glyphosate failure on junglerice control have been reported in the midsouthern U.S., specifically in Mississippi and Tennessee. ARS researchers in Stoneville, Mississippi, conducted research to confirm resistance to glyphosate, measure the magnitude of resistance, and to determine the mechanism(s) of resistance to glyphosate in junglerice populations from Mississippi (MSGR4) and Tennessee (TNGR). The resistance indices of MSGR4 biotype and TNGR population indicated a 4- and 7-fold resistance to glyphosate, respectively, relative to the susceptible MSGS population. The absorption patterns of 14C-glyphosate in the TNGR and MSGS populations were similar. However, the MSGS population translocated 13% more 14C-glyphosate out of the treated leaf compared to the TNGR population. EPSPS gene sequence analyses of TNGR junglerice indicated no point mutations, but several resistant biotypes including MSGR4 possessed a single nucleotide substitution of T for C at codon 106 position, resulting in a proline to serine substitution. Results from qPCR analyses suggested no amplification of the EPSPS gene in the resistant populations and biotypes. Thus, the mechanism of resistance in the MSGR population is, in part, due to a target site mutation at the 106 loci of EPSPS gene, while reduced translocation of glyphosate was found to confer glyphosate resistance in the TNGR population. The above results indicate the necessity of developing junglerice management strategies that include chemical, cultural, and mechanical tools.
3. Multiple herbicide resistance in Italian ryegrass (Lolium perenne ssp. multiforum). ARS researchers in Stoneville, Mississippi, previously confirmed multiple resistance to glyphosate, sethoxydim, and paraquat in two Italian ryegrass populations (MR1 and MR2) in northern California. Preliminary greenhouse studies revealed that both populations were also resistant to imazamox and mesosulfuron, (acetolactate synthase (ALS)-inhibiting herbicides). Three sub-populations, MR1-A and MR1-P (from MR1), and MR2 (from MR2) were studied to determine the resistance level to imazamox and mesosulfuron, evaluate other herbicide options for potential control, and characterize the ALS inhibitor resistance mechanism(s). Based on I50 values, MR1-A, MR-P and MR2 plants was 712, 1104, and 3-fold and 10, 18, and 5-fold less responsive to mesosulfuron and imazamox, respectively, than susceptible plants. Whole-plant and in vitro assays indicated that both MR1 sub-populations were highly resistant to imazamox and mesosulfuron. A point mutation leading to substitution of tryptophan with leucine at 574 loci of ALS conferred resistance in MR1 plants. Plants from all populations were effectively controlled (>99%) with the labeled field rate of glufosinate. Results suggest an altered target-site mechanism of resistance to ALS inhibitors in MR1-A and MR1-P plants and a non-target site resistance in MR2 plants. A combination of chemical, mechanical, and cultural strategies is recommended for control of multiple resistant Italian ryegrass from California and other states in the U.S.
4. Bioherbicide and herbicide interactions for weed control. ARS researchers in Stoneville, Mississippi, previously showed that a strain of Myrothecium verrucaria (MV) exhibited bioherbicidal activity against several important weeds (including glyphosate-resistant Palmer amaranth), that some commercial formulations of glyphosate applied with MV resulted in synergistic interactions that improved weed control efficacy, and that some commercial formulations were inhibitory to MV. Further studies tested the effect of unformulated glyphosate (high purity, technical-grade glyphosate) alone and combined with MV for bioherbicidal activity on glyphosate-susceptible and -resistant Palmer amaranth biotypes under greenhouse conditions and examined technical-grade glyphosate effects on the growth of MV. High purity glyphosate (without adjuvants/surfactants) was not toxic to MV growth and sporulation at concentrations up to 2.0 mM when grown on agar supplemented with the herbicide. Both biotypes were injured by MV and MV plus glyphosate treatments as early as 19 h after application (3 h after a dew period of 16 h). These injury effects increased and were more prominent through the 6-day time course, and after 120 h the MV plus glyphosate treatment resulted in mortality of the glyphosate-susceptible and -resistant plants. The glyphosate plus MV interaction was synergistic toward the control of Palmer amaranth. Results demonstrated that MV can control both glyphosate-resistant and -susceptible Palmer amaranth seedlings and it can act synergistically with high-purity glyphosate to provide improved weed control.
Nandula, V.K., Riechers, D.E., Ferhatoglu, Y., Barrett, M., Duke, S.O., Dayan, F.E., Goldberg-Cavalleri, A., Tetard-Jones, C., Wortley, D.J., Onkokesugn, N., Brazier-Hicks, M., Edwards, R., Gaines, T., Iwakami, S., Jugulam, M., Ma, R. 2019. Herbicide metabolism: Crop selectivity, bioactivation, weed resistance mechanisms, and regulation. Weed Science. 67:149-175.
Hoagland, R.E., Boyette, C.D., Jordan, R.H., Stetina, K.C. 2018. Interaction of glufosinate and Colletotrichum truncatum on ammonia levels and glutamine synthetase activity in Hemp sesbania. American Journal of Plant Sciences. 9:2320-2337.
Hoagland, R.E., Boyette, C.D., Jordan, R.H., Stetina, K.C. 2018. Interaction of the bioherbicide Myrothecium verrucaria with technical-grade glyphosate on glyphosate-susceptible and -resistant Palmer amaranth. American Journal of Plant Sciences. 9:2306-2319.
Nandula, V.K., Molin, W.T., Bond, J.A. 2018. Influence of water quality, formulation, adjuvant, rainfastness, and nozzle type on efficacy of fomesafen on Palmer Amaranth (Amaranthus palmeri) control. American Journal of Plant Sciences. 9:1660-1676.
Nandula, V.K., Montgomery, G.B., Vennapusa, A.R., Jugulam, M., Giacomini, D.A., Ray, J.D., Bond, J.A., Steckel, L.E., Tranel, P.J. 2018. Glyphosate-resistant junglerice (Echinochloa colona) from Mississippi and Tennessee: Magnitude and resistance mechanisms. Weed Science. 66:603-610.
Boyette, C.D., Hoagland, R.E., Stetina, K.C. 2018. Hot water treatment enhances the bioherbicidal efficacy of a fungus. American Journal of Plant Sciences. 9(10):2063-2076.
Boyette, C.D., Hoagland, R.E., Stetina, K.C. 2019. Extending the host range of the bioherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene. Biocontrol Science and Technology. 29(7):720-726.
Molin, W.T. 2019. How Amaranthus palmeri evolved from an obscure plant of North America to become the biggest weed problem in the US corn and soybean belt. Outlooks on Pest Management. pp. 1-4.
Tehranchian, P., Nandula, V.K., Matzrafi, M., Jasieniuk, M. 2019. Multiple herbicide resistance in California Italian ryegrass (Lolium perenne ssp. multiforum) I: Characterization of ALS-inhibiting herbicide resistance. Weed Science. 67:273-280.
Reddy, K.N., Molin, W.T. 2019. Sustainable weed control in cotton. In: Korres, N.E., Burgos, N.R., and Duke, S.O., editors. Weed Control Sustainability, Hazards and Risks in Cropping Systems Worldwide. Boca Raton, Florida, CRC Press: Taylor and Francis Group. p. 306-324.