The Experts below are selected from a list of 3480 Experts worldwide ranked by ideXlab platform
Bijay K. Singh - One of the best experts on this subject based on the ideXlab platform.
-
Imidazolinone-tolerant Crops: History, Current Status and Future
Pest management science, 2005Co-Authors: Siyuan Tan, Richard R Evans, Mark L. Dahmer, Bijay K. Singh, Dale L. ShanerAbstract:Imidazolinone herbicides, which include imazapyr, imazapic, imazethapyr, imazamox, imazamethabenz and imazaquin, control weeds by inhibiting the enzyme acetohydroxyacid synthase (AHAS), also called acetolactate synthase (ALS). AHAS is a critical enzyme for the biosynthesis of branched-chain amino acids in plants. Several variant AHAS genes conferring Imidazolinone tolerance were discovered in plants through mutagenesis and selection, and were used to create Imidazolinone-tolerant maize (Zea mays L), wheat (Triticum aestivum L), rice (Oryza sativa L), oilseed rape (Brassica napus L) and sunflower (Helianthus annuus L). These crops were developed using conventional breeding methods and commercialized as Clearfield* crops from 1992 to the present. Imidazolinone herbicides control a broad spectrum of grass and broadleaf weeds in Imidazolinone-tolerant crops, including weeds that are closely related to the crop itself and some key parasitic weeds. Imidazolinone-tolerant crops may also prevent rotational crop injury and injury caused by interaction between AHAS-inhibiting herbicides and insecticides. A single target-site mutation in the AHAS gene may confer tolerance to AHAS-inhibiting herbicides, so that it is technically possible to develop the Imidazolinone-tolerance trait in many crops. Activities are currently directed toward the continued improvement of Imidazolinone tolerance and development of new Clearfield* crops. Management of herbicide-resistant weeds and gene flow from crops to weeds are issues that must be considered with the development of any herbicide-resistant crop. Thus extensive stewardship programs have been developed to address these issues for Clearfield* crops.
-
Imidazolinone Resistance in Smooth Pigweed (Amaranthus hybridus) Is Due to an Altered Acetolactate Synthase
Weed Technology, 1999Co-Authors: Brian S. Manley, Dale L. Shaner, Bijay K. Singh, Henry P. WilsonAbstract:Seeds were collected from an Imidazolinone-resistant (R) population of smooth pigweed near Marion, MD, and from an Imidazolinone-susceptible (S) population near Painter, VA, and grown in the greenhouse. Acetolactate synthase (ALS) enzyme was extracted from both biotypes and assayed in the presence of CGA 152005, chlorimuron, halosulfuron, imazaquin, imazethapyr, nicosulfuron, primisulfuron, pyrithiobac, rimsulfuron, and thifensulfuron to determine if an altered ALS was the mechanism of resistance in the R biotype and to determine if this biotype was cross-resistant to other ALS inhibitor herbicides. The inhibitor concentration required to cause a 50% reduction in ALS activity (I 50 ) was calculated for each herbicide. ALS from the R biotype was approximately 71-, 109,000-, and 9-fold more resistant to imazaquin, imazethapyr, and rimsulfuron, respectively, than that from the S biotype. ALS from the R biotype was approximately threefold more sensitive to pyrithiobac and thifensulfuron than that from the S biotype. R ALS was also slightly more tolerant to CGA 152005 and nicosulfuron and slightly more sensitive to primisulfuron and chlorimuron. ALS from both biotypes generally responded similarly to halosulfuron. Resistance in the R biotype was due to an altered form of ALS that is insensitive to the Imidazolinone herbicides and rimsulfuron.
-
Tolerance to Imidazolinone Herbicides in Wheat
Plant physiology, 1992Co-Authors: Keith Elling Newhouse, Wendy A. Smith, Mark A. Starrett, Thomas Joseph Schaefer, Bijay K. SinghAbstract:An Imidazolinone-tolerant wheat (Triticum aestivum L. em Thell) mutant in the winter wheat cultivar Fidel has been identified and characterized. The mutant was isolated from a population derived through seed mutagenesis of the variety with an aqueous solution containing sodium azide. Imidazolinone-tolerant wheat seedlings were selected from the M(2) generation of the population in the presence of imazethapyr herbicide and identified as herbicide-insensitive individuals. The trait is inherited as a single semidominant gene and confers high levels of tolerance to imazethapyr. Acetohydroxyacid synthase activity in extracts from Imidazolinonetolerant plants was less inhibited by imazethapyr than the enzyme from the wild type. The herbicide-tolerant plants have a completely normal phenotype and display no negative effects on growth and yield in either the absence or presence of imazethapyr.
-
Imidazolinone-induced loss of acetohydroxyacid synthase activity in maize is not due to the enzyme degradation.
Plant physiology, 1991Co-Authors: Dale L. Shaner, Bijay K. SinghAbstract:Acetohydroxyacid synthase (AHAS), the first enzyme leading to the biosynthesis of valine, leucine, and isoleucine, is inhibited by different chemical classes of herbicides. There is a loss in the extractable AHAS activity in Imidazolinone-treated plants. Immunological studies using a monoclonal antibody against AHAS revealed no degradation of AHAS protein in Imidazolinone-treated maize (Zea mays) plants. Therefore, the loss in AHAS activity is not due to the loss of AHAS protein.
-
Mutations in corn (Zea mays L.) conferring resistance to Imidazolinone herbicides.
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, 1991Co-Authors: K. Newhouse, Bijay K. Singh, Dale L. Shaner, Mark A. StidhamAbstract:Three corn (Zea mays L.) lines resistant to Imidazolinone herbicides were developed by in vitro selection and plant regeneration. For all three lines, resistance is inherited as a single semidominant allele. The resistance alleles from resistant lines XA17, XI12, and QJ22 have been crossed into the inbred line B73, and in each case homozygotes are tolerant of commercial use rates of Imidazolinone herbicides. All resistant selections have herbicide-resistant forms of acetohydroxyacid synthase (AHAS), the known site of action of Imidazolinone herbicides. The herbicide-resistant phenotypes displayed at the whole plant level correlate directly with herbicide insensitivity of the AHAS activities of the selections. The AHAS activities from all three selections have normal feedback regulation by valine and leucine, and plants containing the mutations display a normal phenotype.
Amit J Jhala - One of the best experts on this subject based on the ideXlab platform.
-
Efficacy of Pre-Emergence and Post-Emergence Soybean Herbicides for Control of Glufosinate-, Glyphosate-, and Imidazolinone-Resistant Volunteer Corn
2016Co-Authors: Parminder S Chahal, Greg Kruger, Humberto Blanco, Amit J JhalaAbstract:Glyphosate-resistant corn and soybean are grown in rotations in the Midwest, including Nebraska. Volunteer corn is a problematic weed in soybean fields because it causes harvest problems, reduces yield and seed quality, and potentially harbors insects, pests, and diseases. Several pre-packaged herbicides have been registered in soybean in recent years, but response of volunteer corn to these herbicides has not yet been documented. Greenhouse experiments were conducted to evaluate the response of glufosinate-, glyphosate-, and Imidazolinone-resistant volunteer corn to 20 pre-emergence (PRE) and 17 post-emergence (POST) soybean herbicides. Cumulative emergence of volunteer corn was not affected by PRE soybean herbicides compared with the nontreated control regardless of herbicide-resistant trait at 21 days after treatment (DAT). Although comparable with several other treatments, clomazone provided ≥ 90 % control of glufosinate- and Imidazolinone-resistant volunteer corn at 21 DAT. The POST soybean herbicides were applied when volunteer corn plants were at the 2 to 3 or 5 to 6 leaf stage. The ACCase-inhibiting herbicides, including clethodim, fenoxaprop plus fluazifop, fluazifop, quizalofop, and sethoxydim, provided ≥ 96 and ≥ 85 % control of the 2 to 3 or 5 to 6 leaf stage volunteer corn, respectively, regardless of the herbicide-resistance trait at 28 DAT. Glyphosate tank mixed with acifluorfen, chlorimuron-ethyl, or Imidazolinones usually provided> 83 % control o
-
efficacy of pre emergence and post emergence soybean herbicides for control of glufosinate glyphosate and Imidazolinone resistant volunteer corn
The Journal of Agricultural Science, 2014Co-Authors: Parminder S Chahal, Greg R Kruger, Humberto Blancocanqui, Amit J JhalaAbstract:Glyphosate-resistant corn and soybean are grown in rotations in the Midwest, including Nebraska. Volunteer corn is a problematic weed in soybean fields because it causes harvest problems, reduces yield and seed quality, and potentially harbors insects, pests, and diseases. Several pre-packaged herbicides have been registered in soybean in recent years, but response of volunteer corn to these herbicides has not yet been documented. Greenhouse experiments were conducted to evaluate the response of glufosinate-, glyphosate-, and Imidazolinone-resistant volunteer corn to 20 pre-emergence (PRE) and 17 post-emergence (POST) soybean herbicides. Cumulative emergence of volunteer corn was not affected by PRE soybean herbicides compared with the nontreated control regardless of herbicide-resistant trait at 21 days after treatment (DAT). Although comparable with several other treatments, clomazone provided ≥ 90% control of glufosinate- and Imidazolinone-resistant volunteer corn at 21 DAT. The POST soybean herbicides were applied when volunteer corn plants were at the 2 to 3 or 5 to 6 leaf stage. The ACCase-inhibiting herbicides, including clethodim, fenoxaprop plus fluazifop, fluazifop, quizalofop, and sethoxydim, provided ≥ 96 and ≥ 85% control of the 2 to 3 or 5 to 6 leaf stage volunteer corn, respectively, regardless of the herbicide-resistance trait at 28 DAT. Glyphosate tank mixed with acifluorfen, chlorimuron-ethyl, or Imidazolinones usually provided > 83% control of glufosinate-and Imidazolinone-resistant volunteer corn when sprayed at the 2 to 3 leaf stage at 28 DAT, but control was ≤ 71% for the 5 to 6 leaf stage volunteer corn. Similar results were usually reflected in volunteer corn biomass. It is concluded that PRE soybean herbicides partially controlled volunteer corn; therefore, ACCase inhibiting herbicides are the only highly effective option for soybean growers.
Dale L. Shaner - One of the best experts on this subject based on the ideXlab platform.
-
Imidazolinone-tolerant Crops: History, Current Status and Future
Pest management science, 2005Co-Authors: Siyuan Tan, Richard R Evans, Mark L. Dahmer, Bijay K. Singh, Dale L. ShanerAbstract:Imidazolinone herbicides, which include imazapyr, imazapic, imazethapyr, imazamox, imazamethabenz and imazaquin, control weeds by inhibiting the enzyme acetohydroxyacid synthase (AHAS), also called acetolactate synthase (ALS). AHAS is a critical enzyme for the biosynthesis of branched-chain amino acids in plants. Several variant AHAS genes conferring Imidazolinone tolerance were discovered in plants through mutagenesis and selection, and were used to create Imidazolinone-tolerant maize (Zea mays L), wheat (Triticum aestivum L), rice (Oryza sativa L), oilseed rape (Brassica napus L) and sunflower (Helianthus annuus L). These crops were developed using conventional breeding methods and commercialized as Clearfield* crops from 1992 to the present. Imidazolinone herbicides control a broad spectrum of grass and broadleaf weeds in Imidazolinone-tolerant crops, including weeds that are closely related to the crop itself and some key parasitic weeds. Imidazolinone-tolerant crops may also prevent rotational crop injury and injury caused by interaction between AHAS-inhibiting herbicides and insecticides. A single target-site mutation in the AHAS gene may confer tolerance to AHAS-inhibiting herbicides, so that it is technically possible to develop the Imidazolinone-tolerance trait in many crops. Activities are currently directed toward the continued improvement of Imidazolinone tolerance and development of new Clearfield* crops. Management of herbicide-resistant weeds and gene flow from crops to weeds are issues that must be considered with the development of any herbicide-resistant crop. Thus extensive stewardship programs have been developed to address these issues for Clearfield* crops.
-
Imidazolinone-resistant wheat acetolactate synthase in vivo response to imazamox
Weed Technology, 2005Co-Authors: Curtis R Rainbolt, Donald C Thill, Robert S. Zemetra, Dale L. ShanerAbstract:Several experiments were conducted to evaluate the utility of an in vivo acetolactate synthase (ALS) assay for comparing sensitivity to imazamox among Imidazolinone-resistant wheat cultivars/lines. Ten single-gene Imidazolinone-resistant winter wheat cultivars/lines, one two-gene and four single-gene Imidazolinone-resistant spring wheat cultivars/lines, and three pairs of heterozygous and homozygous Imidazolinone-resistant winter wheat lines were evaluated in the assay experiments. Additionally, a dose-response assay was conducted to evaluate the tolerance of several Imidazolinone-resistant wheat cultivars to imazamox on a whole plant level. The I50 value (i.e., the imazamox dose that inhibited ALS activity by 50%) of the winter wheat cultivar ‘Above’ was 54 to 84% higher than the I50 values of 99-420, 99-433, and CV-9804. However, based on the results of this study, it is unclear whether genetic background or market class (hard red winter vs. soft white winter) influences the level of ALS inhibition by i...
-
Imidazolinone Resistance in Smooth Pigweed (Amaranthus hybridus) Is Due to an Altered Acetolactate Synthase
Weed Technology, 1999Co-Authors: Brian S. Manley, Dale L. Shaner, Bijay K. Singh, Henry P. WilsonAbstract:Seeds were collected from an Imidazolinone-resistant (R) population of smooth pigweed near Marion, MD, and from an Imidazolinone-susceptible (S) population near Painter, VA, and grown in the greenhouse. Acetolactate synthase (ALS) enzyme was extracted from both biotypes and assayed in the presence of CGA 152005, chlorimuron, halosulfuron, imazaquin, imazethapyr, nicosulfuron, primisulfuron, pyrithiobac, rimsulfuron, and thifensulfuron to determine if an altered ALS was the mechanism of resistance in the R biotype and to determine if this biotype was cross-resistant to other ALS inhibitor herbicides. The inhibitor concentration required to cause a 50% reduction in ALS activity (I 50 ) was calculated for each herbicide. ALS from the R biotype was approximately 71-, 109,000-, and 9-fold more resistant to imazaquin, imazethapyr, and rimsulfuron, respectively, than that from the S biotype. ALS from the R biotype was approximately threefold more sensitive to pyrithiobac and thifensulfuron than that from the S biotype. R ALS was also slightly more tolerant to CGA 152005 and nicosulfuron and slightly more sensitive to primisulfuron and chlorimuron. ALS from both biotypes generally responded similarly to halosulfuron. Resistance in the R biotype was due to an altered form of ALS that is insensitive to the Imidazolinone herbicides and rimsulfuron.
-
Imidazolinone-induced loss of acetohydroxyacid synthase activity in maize is not due to the enzyme degradation.
Plant physiology, 1991Co-Authors: Dale L. Shaner, Bijay K. SinghAbstract:Acetohydroxyacid synthase (AHAS), the first enzyme leading to the biosynthesis of valine, leucine, and isoleucine, is inhibited by different chemical classes of herbicides. There is a loss in the extractable AHAS activity in Imidazolinone-treated plants. Immunological studies using a monoclonal antibody against AHAS revealed no degradation of AHAS protein in Imidazolinone-treated maize (Zea mays) plants. Therefore, the loss in AHAS activity is not due to the loss of AHAS protein.
-
Mutations in corn (Zea mays L.) conferring resistance to Imidazolinone herbicides.
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, 1991Co-Authors: K. Newhouse, Bijay K. Singh, Dale L. Shaner, Mark A. StidhamAbstract:Three corn (Zea mays L.) lines resistant to Imidazolinone herbicides were developed by in vitro selection and plant regeneration. For all three lines, resistance is inherited as a single semidominant allele. The resistance alleles from resistant lines XA17, XI12, and QJ22 have been crossed into the inbred line B73, and in each case homozygotes are tolerant of commercial use rates of Imidazolinone herbicides. All resistant selections have herbicide-resistant forms of acetohydroxyacid synthase (AHAS), the known site of action of Imidazolinone herbicides. The herbicide-resistant phenotypes displayed at the whole plant level correlate directly with herbicide insensitivity of the AHAS activities of the selections. The AHAS activities from all three selections have normal feedback regulation by valine and leucine, and plants containing the mutations display a normal phenotype.
Valmir Gaedke Menezes - One of the best experts on this subject based on the ideXlab platform.
-
Rapid diagnosis of resistance to Imidazolinone herbicides in barnyardgrass (Echinochloa crus-galli) and control of resistant biotypes with alternative herbicides
Planta Daninha, 2013Co-Authors: Felipe De Oliveira Matzenbacher, A. Kalsing, Valmir Gaedke Menezes, J.a.n. Barcelos, A. Merotto JuniorAbstract:The resistance of barnyardgrass (Echinochloa crus-galli) to Imidazolinone herbicides is a worldwide problem in paddy fields. A rapid diagnosis is required for the selection of adequate prevention and control practices. The objectives of this study were to develop expedite bioassays to identify the resistance to Imidazolinone herbicides in barnyardgrass and to evaluate the efficacy of alternative herbicides for the post-emergence control of resistant biotypes. Three experiments were conducted to develop methods for diagnosis of resistance to imazethapyr and imazapyr + imazapic in barnyardgrass at the seed, seedling and tiller stages, and to carry out a pot experiment to determine the efficacy of six herbicides applied at post-emergence in 13 biotypes of barnyardgrass resistant to Imidazolinones. The seed soaking bioassay was not able to differentiate the resistant and susceptible biotypes. The resistance of barnyardgrass to Imidazolinones was effectively discriminated in the seedlings and tiller bioassays seven days after incubation at the concentrations of 0.001 and 0.0001 mM, respectively, for both imazethapyr and imazapyr + imazapic. The biotypes identified as resistant to Imidazolinones showed different patterns of susceptibility to penoxsulam, bispyribac-sodium and pyrazosulfuron-ethyl, and were all controlled with profoxydim and cyhalofop-butyl. The seedling and tiller bioassays are effective in the diagnosis of barnyardgrass resistance to Imidazolinone herbicides, providing an on-season opportunity to identify the need to use alternative herbicides to be applied at post-emergence for the control of the resistant biotypes.
-
regional scale distribution of Imidazolinone herbicide resistant alleles in red rice oryza sativa l determined through snp markers
Field Crops Research, 2010Co-Authors: A C Roso, Aldo Merotto, Carla Andrea Delatorre, Valmir Gaedke MenezesAbstract:Abstract Red rice is the main weed in rice paddy fields. Imidazolinone herbicides in resistant rice cultivars currently provide a unique opportunity to control red rice in large-scale rice fields. However, the continuous use of this technology has resulted in Imidazolinone-resistant red rice biotypes. This study aimed to identify the mechanism of herbicide resistance and the frequency and spatial distribution of the known Imidazolinone herbicide-resistant alleles in red rice. The nucleotide sequence of the ALS gene indicated that the G 654 E, S 653 D and A 122 T mutations are present in the Imidazolinone herbicide-resistant rice cultivars IRGA 422 CL, SATOR CL and PUITA INTA CL, respectively. This information and the nucleotide sequence surrounding these mutations were used for the development of single nucleotide polymorphism (SNP) molecular markers to identify the possible mutations that confer herbicide resistance in red rice. This analysis was carried out in a total of 481 plants from 38 populations collected as individuals that escaped control with the herbicides imazethapyr and imazapic in rice paddy fields in Southern Brazil. The G 654 E mutation was the most frequent, being found in 100% and 90.9% of the populations in the 2006/2007 and 20007/2008 seasons, respectively. In addition, the S 653 D and A 122 T mutations were also present either alone or as double or triple mutations in some plants. Target site insensitivity is the predominant mechanism of resistance in red rice resistant to Imidazolinone herbicides in Southern Brazil. The high frequency of the S 653 D mutation, the same mutation responsible for the resistance in the rice cultivar largely used in Southern Brazil, indicates that gene flow is occurring from the rice cultivar to red rice. Management practices related to increasing crop sanitation and decreasing of herbicide selection pressure through crop rotation should be enforced to prevent the evolution of herbicide resistance in red rice.
Aldo Merotto - One of the best experts on this subject based on the ideXlab platform.
-
antagonism is the predominant effect of herbicide mixtures used for Imidazolinone resistant barnyardgrass echinochloa crus galli control
Planta Daninha, 2015Co-Authors: Felipe De Oliveira Matzenbacher, A. Kalsing, Giliardi Dalazen, Catarine Markus, Aldo MerottoAbstract:Herbicides mixtures are used in many situations without the adequate knowledge related with the effect on major target weeds. The objective of this study was to evaluate the effects of different herbicides mixtures used in irrigated rice in order to establish the adequate combinations for the prevention and management of herbicide resistance in barnyardgrass (Echinochloa crus-galli). Three experiments were performed at field conditions with all major post-emergent herbicides used in irrigated rice in Brazil. The first experiment was performed with barnyardgrass resistant to Imidazolinone herbicides and herbicides applied at label rates. The second and third experiments were performed with barnyardgrass resistant and susceptible to Imidazolinone herbicides applied at doses of 50 or 75% of the label rates. The occurrence of additive, synergistic and antagonistic effects was identified at 18, 18 and 64%, respectively, among the total of 50 different associations of herbicide and rates evaluated. In general, the mixture of ACCase inhibitors with ALS inhibitors, quinclorac, clomazone + propanil or thiobencarb resulted in antagonism. Sinergic mixtures were found in clomazone with propanil + thiobencarb, profoxydim with cyhalofop-butyl or clomazone, and quinclorac with imazapyr + imazapic, bispyribac-sodium or cyhalofop-butyl. The mixtures of quinclorac with profoxydim were antagonic. Rice grain yield varied according to the efficiency of weed control. Seveveral mixtures were effective for Imidazolinone resistant barnyardgrass control.
-
Identification of origin and analysis of population structure of field-selected Imidazolinone-herbicide resistant red rice ( Oryza sativa )
Euphytica, 2012Co-Authors: Ives Clayton Gomes Dos Reis Goulart, Marcelo Teixeira Pacheco, Anderson Luis Nunes, Aldo MerottoAbstract:Several red rice biotypes have evolved resistance to Imidazolinone herbicides. The origin of resistance has been attributed to gene flow from the herbicide-resistant rice cultivars, but independent evolution of spontaneous mutation can also contribute to the herbicide resistance. The objective of this study was to quantify the occurrence of gene flow and independent selection as the mechanisms of origin of Imidazolinone-resistance in red rice to correctly define the management practices for red rice control. Three single nucleotide polymorphism markers were used to identify acetolactate synthase (ALS) gene mutations, and four simple sequence repeat markers were used to identify hybrids of Imidazolinone-resistant rice cultivars and red rice. In addition, genetic diversity and population structure analyses were performed. Artificial hybrids were used as controls. Gene flow was the main origin of Imidazolinone herbicide resistance, but independent selection occurred in 1.1 % of the evaluated red rice plants. Two red rice plants that independently evolved herbicide resistance had the ALS gene mutation, Gly654Glu. Population structure analysis also indicated intense gene flow from rice cultivars to red rice, but some populations maintained a high genetic identity based on a small amount of gene introgression from the rice cultivars. These results indicate the importance of adopting controls of red rice escapees to avoid gene flow from the Imidazolinone-resistant rice, and the necessity of biotechnological approaches to mitigating gene flow in the development of new herbicide-resistant rice cultivars.
-
differential germination pattern of rice cultivars resistant to Imidazolinone herbicides carrying different acetolactate synthase gene mutations
Weed Research, 2012Co-Authors: F O Matzenbacher, I C G R Goulart, Aldo MerottoAbstract:Goulart ICGR, Matzenbacher FO & Merotto A JR (2012). Differential germination pattern of rice cultivars resistant to Imidazolinone herbicides carrying different acetolactate synthase gene mutations. Weed Research52, 224–232. Summary Different mutations in the acetolactate synthase (ALS) gene can affect the germination pattern and facilitate the occurrence of ALS-inhibiting herbicide resistance in weedy red rice. The aim of this study was to evaluate the germination rates in Imidazolinone-resistant rice cultivars carrying three different ALS gene mutations. Plant material consisted of the Imidazolinone-resistant rice cultivars IRGA 422 CL, PUITA INTA CL and SATOR CL that carry the ALS mutations Gly654Glu, Ala122Thr and Ser653Asn, respectively, and the susceptible cultivar IRGA 417. Initially, the germination pattern of these cultivars was evaluated at temperatures of 15, 20, 25 and 30°C. Afterwards, five lots of each cultivar were evaluated at temperatures of 20 and 25°C to separate the environmental and genotypic effects. The environmental effect related to the different seed origin did not affect the germination rates of the rice cultivars. However, the germination pattern of the evaluated cultivars was different, mainly at 20°C. The time to reach 50% germination at 20°C for the Imidazolinone-resistant rice cultivars IRGA 422 CL, SATOR CL and PUITA INTA CL was 6, 16 and 24 h earlier, respectively, than the susceptible cultivar IRGA 417. The PUITA INTA CL cultivar, which carries the mutation Ala122Thr, showed faster germination than the other herbicide–resistant and the susceptible cultivars at 20°C. The faster germination that resulted from the resistance to ALS-inhibiting herbicides could have different consequences for the establishment and competition of weedy red rice.
-
regional scale distribution of Imidazolinone herbicide resistant alleles in red rice oryza sativa l determined through snp markers
Field Crops Research, 2010Co-Authors: A C Roso, Aldo Merotto, Carla Andrea Delatorre, Valmir Gaedke MenezesAbstract:Abstract Red rice is the main weed in rice paddy fields. Imidazolinone herbicides in resistant rice cultivars currently provide a unique opportunity to control red rice in large-scale rice fields. However, the continuous use of this technology has resulted in Imidazolinone-resistant red rice biotypes. This study aimed to identify the mechanism of herbicide resistance and the frequency and spatial distribution of the known Imidazolinone herbicide-resistant alleles in red rice. The nucleotide sequence of the ALS gene indicated that the G 654 E, S 653 D and A 122 T mutations are present in the Imidazolinone herbicide-resistant rice cultivars IRGA 422 CL, SATOR CL and PUITA INTA CL, respectively. This information and the nucleotide sequence surrounding these mutations were used for the development of single nucleotide polymorphism (SNP) molecular markers to identify the possible mutations that confer herbicide resistance in red rice. This analysis was carried out in a total of 481 plants from 38 populations collected as individuals that escaped control with the herbicides imazethapyr and imazapic in rice paddy fields in Southern Brazil. The G 654 E mutation was the most frequent, being found in 100% and 90.9% of the populations in the 2006/2007 and 20007/2008 seasons, respectively. In addition, the S 653 D and A 122 T mutations were also present either alone or as double or triple mutations in some plants. Target site insensitivity is the predominant mechanism of resistance in red rice resistant to Imidazolinone herbicides in Southern Brazil. The high frequency of the S 653 D mutation, the same mutation responsible for the resistance in the rice cultivar largely used in Southern Brazil, indicates that gene flow is occurring from the rice cultivar to red rice. Management practices related to increasing crop sanitation and decreasing of herbicide selection pressure through crop rotation should be enforced to prevent the evolution of herbicide resistance in red rice.