Lorentz, Lothar: Herbicide Resistance : Molecular and Physiological Characterization of the Glyphosate Resistant Weeds Amaranthus ssp. and Sorghum ssp.. - Bonn, 2014. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5n-34778
@phdthesis{handle:20.500.11811/5825,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5n-34778,
author = {{Lothar Lorentz}},
title = {Herbicide Resistance : Molecular and Physiological Characterization of the Glyphosate Resistant Weeds Amaranthus ssp. and Sorghum ssp.},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2014,
month = feb,

note = {Herbicides are an important tool for agricultural production to control weeds, avoid soil erosion, and maintain high yields. Highly competitive weeds like Amaranthus ssp. and Sorghum halepense have to be controlled in key crops like corn, cotton and soybean. During the past 30 years glyphosate has proven to be the most cost effective and environmentally benign herbicide controlling weeds without significant resistance development. Since the introduction of glyphosate tolerant crop varieties the development of glyphosate resistance has increased dramatically and is today in the Southeast U.S. the most important threat to cropping systems. In order to maintain a sustainable agricultural production, weed resistance mechanisms and their spread in weed populations have to be better characterized and understood.
The response of several Amaranthus palmeri and Amaranthus tuberculatus populations, to the herbicide glyphosate was studied and for most of them resistance was detected or confirmed. Neither a reduction of glyphosate uptake or translocation, nor a mutation in glyphosate target enzyme EPSPS at the amino acid position G101, T101 or P106 was detected in glyphosate resistant plants. The analysis of EPSPS gene copy number revealed that almost all glyphosate resistant populations possessed variable but high EPSPS gene copy number, correlated with its expression both at the RNA and protein levels and with the resistance level observed in the greenhouse. In resistant A. tuberculatus the EPSPS gene amplification and the expressed resistance factors found were lower than in A. palmeri. Nevertheless, one might conclude that the EPSPS gene amplification is the main glyphosate resistance mechanism in A. tuberculatus populations analyzed. In A. palmeri EPSPS gene amplification is the most common and most important resistance mechanism found so far as shown by its widespread geographical occurrence, but it is not the only resistance mechanism developed by this weed species. RAPD analysis of several glyphosate sensitive and resistant A. palmeri populations reveals a stronger relationship based on glyphosate response than based on geographical separation. This suggests that glyphosate resistant individuals have a common ancestor plant or population. These data are discussed related to plant migration, in particular plant seed dispersal, which seems often to be underestimated. These findings stress the importance of farm and field hygiene for weed management to prevent field infection with nearly uncontrollable weeds and lastly to protect efficient crop production.
A Sorghum halepense (Johnsongrass) population collected in AR, U.S.A. was found resistant to glyphosate and to APP ACCase inhibitors. The resistances were confirmed in greenhouse experiments. The resistance of mature plants to glyphosate was moderate, with a resistance factor of 3.6. The EPSPS gene sequence was analyzed for the known mutation sites G101, T102 and P106, but no changes were detected. A heterozygous target site mutation, W2027C, on the ACCase gene sequence was found to cause the resistance to the ACCase inhibitors fluazifop-p-butyl and decreases the sensitivity to quizalofop and clethodim. In this tetraploid species, plants possessing 2 mutated ACCase alleles, out of a total of 4, were shown to be less affected by APP ACCase inhibitor treatments than individuals possessing a single mutated ACCase allele. To our knowledge, this is the first S. halepense population with a reported multiple herbicide resistance showing a specific target site mutation conferring resistance to ACCase herbicides. Moreover it is one of the rare evidence showing that the herbicide resistance observed is directly correlated to the number of mutated alleles.},

url = {http://hdl.handle.net/20.500.11811/5825}
}

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