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Stoneville, MS, United States

Stetina S.R.,U.S. Department of Agriculture | Molin W.T.,Crop Production Systems Research Unit
Journal of Cotton Science | Year: 2014

Reniform nematode (Rotylenchulus reniformis) resistance is being transferred to Gossypium hirsutum from its distant relatives. Reports of fluometuron damage to LONREN lines with nematode resistance from G. longicalyx raised concerns about introducing herbicide sensitivity from other nematode resistance sources. The research objective was to evaluate 15 sources of reniform nematode resistance for their reaction to fluometuron three weeks after planting in a replicated greenhouse trial: two G. herbaceum accessions, four G. arboreum accessions, three G. barbadense accessions, three G. hirsutum accessions, and three G. hirsutum lines with resistance introgressed from G. barbadense (FR-05) or G. longicalyx (LONREN-1 and LONREN-2). The control genotype was G. hirsutum cultivar Deltapine 161 B2RF. Across all herbicide rates tested, mean herbicide injury ratings for G. arboreum accessions were greater than the control, whereas G. barbadense GB 713 and TX 110 were less. Regression analysis of herbicide rates indicated that injury increased linearly with increasing herbicide rate for all accessions, although G. arboreum A2-083 had more injury than the control. Regression analysis of herbicide rates indicated that biomass decreased linearly with increasing herbicide rate for all accessions, although G. barbadense GB 713 and Pima PHY 800 exhibited greater biomass reduction than the control. Across all herbicide rates tested, mean electron transport rates of all G. herbaceum and G. arboreum accessions and G. barbadense Pima PHY 800 were lower than the control. The relationship between herbicide rate and electron transport rate was curvilinear, with similar decreases in electron transport rate in response to increasing herbicide concentration for all lines. Increased sensitivity to fluometuron could be introduced into G. hirsutum through crosses with distantly related species, but with the exception of G. arboreum A2-083, the lines did not respond to the herbicide differently from the control. © The Cotton Foundation 2014.

Teaster N.D.,Samuel Roberts Noble Foundation | Teaster N.D.,Crop Production Systems Research Unit | Keereetaweep J.,University of North Texas | Kilaru A.,East Tennessee State University | And 6 more authors.
Frontiers in Plant Science | Year: 2012

N-acylethanolamines (NAEs are bioactive lipids derived from the hydrolysis of the membrane phospholipid N-acylphosphatidylethanolamine (NAPE. In animal systems this reaction is part of the "endocannabinoid" signaling pathway, which regulates a variety of physiological processes. The signaling function of NAE is terminated by fatty acid amide hydrolase (FAAH, which hydrolyzes NAE to ethanolamine and free fatty acid. Our previous work in Arabidopsis thaliana showed that overexpression of AtFAAH (At5g64440 lowered endogenous levels of NAEs in seeds, consistent with its role in NAE signal termination. Reduced NAE levels were accompanied by an accelerated growth phenotype, increased sensitivity to abscisic acid (ABA, enhanced susceptibility to bacterial pathogens, and early flowering. Here we investigated the nature of the early flowering phenotype of AtFAAH overexpression. AtFAAH overexpressors flowered several days earlier than wild type and AtFAAH knockouts under both non-inductive short day (SD and inductive long day (LD conditions. Microarray analysis revealed that the FLOWERING LOCUS T (FT gene, which plays a major role in regulating flowering time, and one target MADS box transcription factor, SEPATALLA3 (SEP3, were elevated in AtFAAH overexpressors. Furthermore, AtFAAH overexpressors, with the early flowering phenotype had lower endogenous NAE levels in leaves compared to wild type prior to flowering. Exogenous application of NAE 12:0, which was reduced by up to 30% in AtFAAH overexpressors, delayed the onset of flowering in wild type plants. We conclude that the early flowering phenotype of AtFAAH overexpressors is, in part, explained by elevated FT gene expression resulting from the enhanced NAE hydrolase activity of AtFAAH, suggesting that NAE metabolism may participate in floral signaling pathways. © 2012 Teaster, Keereetaweep, Kilaru, Wang, Tang, Tran, Ayre, Chapman and Blancaflor.

Weaver M.A.,Biological Control of Pests Research Unit | Boyette C.D.,Biological Control of Pests Research Unit | Hoagland R.E.,Crop Production Systems Research Unit
Biocontrol Science and Technology | Year: 2016

Among the most important and visible weeds in the Southeastern USA is the exotic invasive vine, kudzu (Pueraria montana var. lobata). Efforts to eradicate it typically involve many years of application of restricted-use pesticides. Recent availability of effective, non-restricted-use pesticides and developments with the application of the bioherbicide Myrothecium verrucaria has made possible new control programmes for kudzu management. Field trials at three sites over two years with aminocyclopyrachlor, aminopyralid, fluroxypyr, metsulfuron methyl and combinations of these herbicides achieved 99–100% reduction in aboveground kudzu biomass. Additionally, programmes were developed that eradicated kudzu while simultaneously establishing native vegetation. One of these successful programmes integrated bioherbicide application, mechanical removal of kudzu biomass and planting switchgrass (Panicum virgatum) in an entirely chemical herbicide-free system. These field tests demonstrate a variety of methods that can be used independently or in an integrated approach for rapid kudzu eradication. ©, The work was authored as part of the Authors' official duties as employees of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105 no copyright protection is available for such works under U.S. law.

Ribeiro D.N.,Mississippi State University | Pan Z.,Natural Products Utilization Research Unit | Duke S.O.,Natural Products Utilization Research Unit | Nandula V.K.,Crop Production Systems Research Unit | And 3 more authors.
Planta | Year: 2014

The inheritance of glyphosate resistance in two Amaranthus palmeri populations (R1 and R2) was examined in reciprocal crosses (RC) and second reciprocal crosses (2RC) between glyphosate-resistant (R) and -susceptible (S) parents of this dioecious species. R populations and Female-R × Male-S crosses contain higher 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene copy numbers than the S population. EPSPS expression, EPSPS enzyme activity, EPSPS protein quantity, and level of resistance to glyphosate correlated positively with genomic EPSPS relative copy number. Transfer of resistance was more influenced by the female than the male parent in spite of the fact that the multiple copies of EPSPS are amplified in the nuclear genome. This led us to hypothesize that this perplexing pattern of inheritance may result from apomictic seed production in A. palmeri. We confirmed that reproductively isolated R and S female plants produced seeds, indicating that A. palmeri can produce seeds both sexually and apomictically (facultative apomixis). This apomictic trait accounts for the low copy number inheritance in the Female-S × Male-R offsprings. Apomixis may also enhance the stability of the glyphosate resistance trait in the R populations in the absence of reproductive partners. © 2013 Springer-Verlag Berlin Heidelberg.

Queiroz S.C.N.,EMBRAPA - Empresa Brasileira de Pesquisa Agropecuaria | Cantrell C.L.,National United University | Duke S.O.,National United University | Wedge D.E.,National United University | And 3 more authors.
Journal of Agricultural and Food Chemistry | Year: 2012

Conyza canadensis (L.) Cronquist syn. (horseweed) is a problematic and invasive weed with reported allelopathic properties. To identify the phytotoxic constituents of the aerial parts, a systematic bioactivity-guided fractionation of the dichloromethane extract was performed. Three active enyne derivatives, (2Z,8Z)-matricaria acid methyl ester, (4Z,8Z)-matricaria lactone, and (4Z)-lachnophyllum lactone, were identified. The lactones inhibited growth of the monocot Agrostis stolonifera (bentgrass) and the dicot Lactuca sativa (lettuce) at 1 mg mL-1, while the (2Z,8Z)-matricaria acid methyl ester was less active. In a dose-response screening of the lactones for growth inhibitory activity against Lemna paucicostata, (4Z)-lachnophyllum lactone was the most active with an IC50 of 104 μM, while the (4Z,8Z)-matricaria lactone was less active (IC50 of 220 μM). In a fungal direct bioautography assay, the two lactones at 10 and 100 μg/spot inhibited growth of the plant pathogenic fungi Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides. In a dose-response screening of the lactones against six different plant pathogenic fungi, (4Z,8Z)-matricaria lactone was more active than the commercial fungicide azoxystrobin on Col. acutatum, Col. fragariae, and Col. gloeosporioides at 30 μM and about as active as the commercial fungicide captan against Col. gloeosporioides, while (4Z)-lachnophyllum lactone was less active. © 2012 American Chemical Society.

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