Patterns Of Resistance To Als Herbicides In Smallflower Umbrella Sedge (Cyperus Difformis) And Ricefield Bulrush (Schoenoplectus Mucronatus) 1 (original) (raw)
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Cross-Resistance of Rice Flatsedge to Als-Inhibiting Herbicides
Planta Daninha, 2017
Cyperus iria (CYPIR) is one of the main weeds in irrigated rice crops. The intense chemical control with acetolactate synthase (ALS) inhibiting herbicides favors the selection of cross-resistance. This study aimed to evaluate the crossresistance of CYPIR to ALS-inhibiting herbicides in irrigated rice in Rio Grande do Sul. Two experiments arranged in a factorial scheme, in a completely randomized design, with four replications were conducted. Experiment I consisted of resistant (CYPIR-R) and susceptible (CYPIR-S) biotypes and ALS-inhibiting herbicide doses: imazethapyr (106 g a.i. ha-1); pyrazosulfuron-ethyl (20 g a.i. ha-1); penoxsulam (36 g a.i. ha-1) and, as an alternative herbicide, bentazone (960 g a.i. ha-1); corresponding to 0; 1/16; 1/8; 1/4; 1/2; 1; 2; 4; 8 and 16x (x = maximum registered dose). Experiment II followed the same procedures, with doses of 0; 1/64; 1/32; 1/16; 1/8; 1/4; 1/2; 1 and 2x for CYPIR-S and 0; 1/2; 1; 2; 4; 8; 16; 32; 64 and 128x for CYPIR-R; including ...
Weed Science, 2015
Smallflower umbrella sedge is a problematic weed in direct-seeded rice in the midsouthern United States. It recently has evolved resistance to the acetolactate synthase (ALS) –inhibiting herbicide halosulfuron in Arkansas rice. Studies were conducted (1) to determine if the resistant biotype is cross resistant to other ALS-inhibiting herbicides, (2) to evaluate alternative herbicide control options, and (3) to determine the mechanism of resistance. Whole-plant bioassay revealed that halosulfuron-resistant plants were not controlled by bispyribac–sodium, imazamox, and penoxsulam at the labeled field rate of each herbicide. The level of resistance to these herbicides, based on the lethal dose needed to kill 50% of plants (LD50) was ≥ 15-fold compared to a susceptible biotype. Both biotypes were controlled >96% with bentazon and propanil and ≤ 23% with quinclorac, thiobencarb, and 2,4-D. Hence, effective control measures exist; albeit, the number of herbicide options appear limited....
Determining the extent of herbicide resistance in the rice growing regions of southern Australia
… people, planet, profit. …, 2004
Weed seed samples were collected in 1999 from across the rice-growing regions of southern New South Wales (NSW). These samples were tested against a relevant range of commercial herbicides to establish benchmark levels of resistance for each weed and herbicide combination. High levels of resistance to bensulfuron were detected in the three weed species tested. Approximately 50 % of dirty dora (Cyperus difformis), 40 % of starfruit (Damasonium minus R.Br. Buch.) and 38 % of arrowhead (Sagittaria montevidensis Cham. & Schlechter) samples were resistant. All dirty dora, arrowhead and starfruit samples were susceptible to all of the other herbicides tested. No barnyard grass samples were classed as resistant to any of the four herbicides tested. A total of six barnyard grass species (barnyard grass (Echinochloa crus-galli (L.) Beauv.), awnless barnyard grass (E. colona (L.) Link), hairy millet (E. oryzoides (Ard.) Fritsch), prickly barnyard grass (E. microstachya (Wieg.) Rydb), Japanese millet (E. esculenta (A Br.) H Scholz) and channel millet (E. inundata Michael et Vickery)) were detected. Four species were collected during a first survey (1999) and five in the second (2001). Three of the six species were present in both surveys. In a number of the samples two different species were present. These species had slightly different rates of germination that resulted in them being at slightly different growth stages at the time of herbicide application. Where mixed populations occur in the field this is of major importance when dealing with any herbicides that have a narrow range of growth stages for effective application. At present, herbicide resistance in weeds of rice appears to be confined to bensulfuron. However it remains important for farmers to implement appropriate herbicide resistance management in order to protect the viability of the herbicide options.
Weed Science, 2015
Overuse of acetolactate synthase (ALS)–inhibiting herbicides in rice has led to the evolution of halosulfuron-resistant rice flatsedge in Arkansas and Mississippi. Resistant accessions were cross-resistant to labeled field rates of ALS-inhibiting herbicides from four different families, in comparison to a susceptible (SUS) biotype. Resistance index of Arkansas and Mississippi accessions based on an R/S ratio of the lethal dose required for 50% plant mortality (LD50) to bispyribac-sodium, halosulfuron, imazamox, and penoxsulam was ≥ 21-fold. Control of Arkansas, Mississippi, and SUS accessions with labeled field rates of 2,4-D, bentazon, and propanil was ≥ 93%. An enzyme assay revealed that an R/S ratio for 50% inhibition (I50) of ALS for halosulfuron was 2,600 and 200 in Arkansas and Mississippi, respectively. Malathion studies did not reveal enhanced herbicide metabolism in resistant plants. The ALS enzyme assay and cross-resistance studies point toward altered a target site as the...
Archives of Biological Sciences
Acetolactate synthase (ALS)-inhibiting herbicides play an important role in controlling broad-leaved weeds. Populations of Sagittaria trifolia L. showed resistance to ALS-inhibiting sulfonylurea herbicides (e.g. bensulfuron-methyl) in paddy fields in the northeast of China. In our study, whole-plant bioassays were performed on eight suspected resistant S. trifolia populations that showed high levels of resistance to bensulfuron-methyl, with resistance indices from 31.06 to 120.35. The results of ALS-activity assays were consistent with the observed whole-plant dose-response data. This confirmed that resistant populations displayed significantly higher ALS activity than the sensitive population due to prevention of normal enzyme-herbicide interaction. The mutations Pro-197-Ser, Pro-197-His, Pro-197-Thr and Pro-197-Leu were identified in the ALS gene of resistant populations. Pro-197-His and Pro-197-Thr mutations conferring resistance to bensulfuron-methyl are reported for the first time in S. trifolia. All resistant populations were resistant to sulfonylurea (SU) herbicides, but not to imidazolinone (IMI) herbicides. HLJ-5 and JL-3 populations were resistant to bispyribac-sodium of the pyrimidinylthiobenozoate (PTB) class of ALS herbicides, JL-2 to penoxsulam of triazolopyrimidine (TP) class and JL-1 to pyribenzoxim, also of PTB class. The eight S. trifolia populations were susceptible to other herbicide modes of action tested.
Weed Science, 2019
Multiple resistance to glyphosate, sethoxydim, and paraquat was previously confirmed in two Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] populations, MR1 and MR2, in northern California. Preliminary greenhouse studies revealed that both populations were also resistant to imazamox and mesosulfuron, both of which are acetolactate synthase (ALS)-inhibiting herbicides. In this study, three subpopulations, MR1-A (from seed of MR1 plants that survived a 16X rate of sethoxydim), MR1-P (from seed of MR1 plants that survived a 2X rate of paraquat), and MR2 (from seed of MR2 plants that survived a 16X rate of sethoxydim), were investigated to determine the resistance level to imazamox and mesosulfuron, evaluate other herbicide options for the control of these multiple resistant L. perenne ssp. multiflorum, and characterize the underlying ALS-inhibitor resistance mechanism(s). Based on LD 50 values, the MR1-A, MR1-P, and MR2 subpopulations were 38-, 29-, 8-fold and 36-, 64-, and 3-fold less sensitive to imazamox and mesosulfuron, respectively, relative to the susceptible (Sus) population. Only MR1-P and MR2 plants were cross-resistant to rimsulfuron, whereas both MR1 subpopulations were cross-resistant to imazethapyr. Pinoxaden (ACCase inhibitor [phenylpyrazoline 'DEN']) only controlled MR2 and Sus plants at the labeled field rate. However, all plants were effectively controlled (>99%) with the labeled field rate of glufosinate. Based on I 50 values, MR1-A, MR-P, and MR2 plants were 712-, 1,104-, and 3-fold and 10-, 18-, and 5-fold less responsive to mesosulfuron and imazamox, respectively, than the Sus plants. Sequence alignment of the ALS gene of resistant plants revealed a missense singlenucleotide polymorphism resulting in a Trp-574-Leu substitution in MR1-A and MR1-P plants, heterozygous in both, but not in the MR2 plants. An additional homozygous substitution, Asp-376-Glu, was identified in the MR1-A plants. Addition of malathion or piperonyl butoxide did not alter the efficacy of mesosulfuron on MR2 plants. In addition, the presence of 2,4-D had no effect on the response of mesosulfuron on the MR2 and Sus. These results suggest an altered target site is the mechanism of resistance to ALS inhibitors in MR1-A and MR1-P plants, whereas a non-target site based resistance apparatus is present in the MR2 plants.
Pest management science, 2014
Yellow nutsedge is one of the most problematic sedges in Arkansas rice, requiring the frequent use of halosulfuron (sulfonylurea) for its control. In the summer of 2012, halosulfuron at 53 g ha(-1) (labeled field rate) failed to control yellow nutsedge. The level of resistance to halosulfuron was determined in the putative resistant biotype, and its cross-resistance to other acetolactate synthase (ALS) inhibitors from four different herbicide families. ALS enzyme assays and analysis of the ALS gene were used to ascertain the resistance mechanism. None of the resistant plants was killed by halosulfuron at a dose of 13 568 g ha(-1) (256× the field dose), indicating a high level of resistance. Based on the whole-plant bioassay, the resistant biotype was not controlled by any of the ALS-inhibiting herbicides (imazamox, imazethapyr, penoxsulam, bispyribac, pyrithiobac-sodium, bensulfuron and halosulfuron) tested at the labeled field rate. The ALS enzyme from the resistant biotype was 254...