ALS-Resistant Smallflower Umbrella Sedge (Cyperus difformis) in Arkansas Rice: Physiological and Molecular Basis of Resistance

Abstract

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 halosulfuronresistant 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 (LD 50 ) 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. Based on in vitro ALS enzyme assays, altered target site is the mechanism of resistance to halosulfuron and imazamox. Massively parallel sequencing with the use of the Illumina HiSeq detected an amino acid substitution of Pro 197 -to-His in the resistant biotype that is consistent with ALS-inhibiting herbicide resistance in other weed species. Nomenclature: Bispyribace-sodium; halosulfuron; imazamox; imazethapyr; penoxsulam; smallflower umbrella sedge, Cyperus difformis L.; rice, Oryza sativa L.

A resurrection experiment finds evidence of both reduced genetic diversity and potential adaptive evolution in the agricultural weed Ipomoea purpurea

“…Plants were harvested, dried at 72°C for 48 h and measured for total above ground biomass. Biomass values were adjusted to the nonsprayed controls by dividing each individual by the average biomass of its population grown in the nonspray control treatment following standard protocols (Tehranchian et al 2015). At the time of sampling survival and biomass remaining post-herbicide (3 weeks after herbicide application), none of the plants exhibited signs of regrowth indicating that our measure of resistance does not confound resistance with tolerance (see Baucom & Mauricio 2008).…”

Sensitivity Analysis of Alisma plantago-aquatica L., Cyperus difformis L. and Schoenoplectus mucronatus (L.) Palla to Penoxsulam

“…Calha et al [30] described cross-resistance to the SUs azimsulfuron, bensulfuron-methyl, cinosulfuron, and ethoxysulfuron, but not to imazethapyr (IMI) for A. plantago-aquatica populations collected in rice paddy fields in Portugal. Different patterns of cross-resistance to ALS-Inhibitors were also reported for Italian, North American, and Spanish populations of C. difformis [5,7,31,32], ranging from populations that are resistant only to SU to others cross-resistant to the SUs bensulfuron-methyl, halosulfuron-methyl, orthosulfamuron, imazethapyr (IMI), bispyribac-sodium (PB), penoxsulam (TP), and propoxycarbazonesodium (SCT) [7]. Similarly, previous studies reported S. mucronatus populations having different patterns of cross-resistance in Italy, USA and Chile [8,31,33]).…”

“…Pro197 to His is often associated to resistance to SU but low or moderate to IMI or TP, while Trp574 to Leu confers broad cross-resistance to different ALS-inhibitor groups [8,[33][34][35][36]. However, Pro197 to His has recently been detected in an American C. difformis population that is characterized by a cross-resistance to bispyribac-sodium (PB), halosulfuron (SU), imazamox (IMI), and penoxsulam (TP) [32], so the level of homozygosis for this point mutation in a given individual can probably influence the level and pattern of resistance to ALS-inhibitors. Since different levels of ploidy (diploid and tetraploid) have been reported for C. difformis [36][37][38], the existence of multiple copies of ALS genes could also contribute to modify the pattern and level of resistance conferred by a specific point mutation.…”

The determination of the critical parameters of a gasoline petroleum fractionSB-180 Trinity-Anastasievskoe oil

“…The authors [1,8] calculated the error ΔtPTS for a standard measuring circuit at different temperatures. Since our measurement scheme used a similar measuring potentiometric setting, we will use the results [5,8] to determine the error of temperature measurement. The data of temperature measurement errors are presented in table 3.4.…”

“…To estimate the random error, data on the measurement of specific volumes of water at six isotherms were used. The obtained values were compared with the literature data [8,9]. As an approximate estimate of the random error of our experimental data we can take the total for all isotherms estimate of the standard deviation of the measured specific volumes compared with the literature data:…”