Gene Flow from Transgenic PPO-inhibiting Herbicide-resistant Rice to Weedy Rice, and Agronomic Performance by Their Hybrids

The introduction of Clearfield (CL) rice cultivars resistant to imidazolinone herbicides, acetolactate synthase (ALS) inhibitors, has raised concerns of gene flow to weedy rice genotypes collectively called “red rice” that infest rice-growing areas in the southern United States. This experiment was conducted to study hybridization between CL rice and red rice using simple sequence repeats (SSR) markers, identify mutations in the ALS gene of imazethapyr-resistant red rice, and to detect the introgression of the ALS-resistant gene from CL rice into red rice. Natural outcrossing experiments between CL rice and strawhull (SH) red rice were set up in Stuttgart, AR, in 2002 and 2003. Putative red rice hybrids were detected among volunteer plants in the following year. Hybridization was confirmed using SSR markers, and introgression of the resistant ALS gene from CL rice to red rice was detected by ALS gene sequencing. The ALS gene sequences of U.S. rice cultivars ‘Bengal’ and ‘Cypress’, SH red rice, CL rice (CL161), and imazethapyr-resistant red rice/CL rice hybrids were compared. Nucleotide sequences of the ALS gene from the rice cultivars were identical. Three point mutations were present in the SH red rice ALS gene coding region relative to Bengal/Cypress. One of these resulted in the substitution of Asp630for Glu630. The ALS gene sequences of confirmed hybrids were identical to that of the herbicide-resistant pollen source, CL161. We identified four ALS gene mutations in the herbicide-resistant red rice hybrids relative to the susceptible rice cultivars. One point mutation, resulting in a substitution of Ser653with Asn, was linked to ALS resistance in callus tissue derived from a Kinmaze rice line from Japan. The other three mutations (Ser186—Pro, Lys416—Glu, and Leu662—Pro) are novel. This experiment confirmed that gene flow from imidazolinone-resistant rice resulted in herbicide-resistant red rice plants.

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DETECTING GENE FLOW FROM ALS-RESISTANT HYBRID AND INBRED RICE TO WEEDY RICE USING SINGLE PLANT POLLEN DONORS

Experimental Agriculture ◽

10.1017/s0014479715000058 ◽

2015 ◽

Vol 52 (2) ◽

pp. 237-250 ◽

Cited By ~ 3

Author(s):

I. C. G. R. GOULART ◽

V. G. MENEZES ◽

E. D. BORTOLY ◽

V. KUPAS ◽

A. MEROTTO

Keyword(s):

Gene Flow ◽

Acetolactate Synthase ◽

Outcrossing Rate ◽

Weedy Rice ◽

Rice Cultivars ◽

Red Rice ◽

Single Plant ◽

Herbicide Resistant ◽

Pollen Donor ◽

Plant Pollen

SUMMARYGene flow from herbicide-resistant rice (Oryza sativaL.) cultivars can affect the biodiversity ofOryzaspp. and can result in the lack of opportunity to control weedy rice through selective herbicides. The aim of the present study was to quantify the outcrossing rate from the herbicide-resistant red rice and rice cultivars carrying three different ALS (acetolactate synthase) alleles using a single plant pollen donor approach. A field experiment was performed using the encircle population combination technique. The main plots comprised the pollen-receptor IRGA 417 cultivar or a susceptible biotype of weedy rice, and the subplots comprised the pollen-donor inbred cultivars IRGA 422 CL and PUITÁ INTA CL, the hybrid SATOR CL or a resistant biotype of weedy rice. Among the pollen-donors, the outcrossing rate for pollen receptor susceptible weedy rice and the IRGA 417 cultivar was 0.0344% and 0.0142%, respectively. Rice cultivars carrying theALSgene mutations Ala122Thr, Ser653Asn and Gly654Asn showed a similar outcrossing rate of 0.0243%. The outcrossing rate decreased over a distance of up to 3.5 m from the pollen-donor and was not affected by the wind cardinal direction. The risk of gene flow of herbicide resistance from rice to weedy rice should be reduced through the development of new strategies to contain and mitigate gene flow and of the elimination of weedy rice escapees.

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Coexistence of Weedy Rice and Rice in Tropical America — Gene Flow and Genetic Diversity

Crop Ferality and Volunteerism ◽

10.1201/9781420037999-22 ◽

2005 ◽

pp. 327-344

Keyword(s):

Genetic Diversity ◽

Gene Flow ◽

Weedy Rice ◽

Tropical America

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Pollen-mediated gene flow and transfer of resistance alleles from herbicide-resistant broadleaf weeds

Weed Technology ◽

10.1017/wet.2020.101 ◽

2020 ◽

pp. 1-15

Author(s):

Amit J. Jhala ◽

Jason K. Norsworthy ◽

Zahoor A. Ganie ◽

Lynn M. Sosnoskie ◽

Hugh J. Beckie ◽

...

Keyword(s):

Gene Flow ◽

Reproductive Biology ◽

Interspecific Hybridization ◽

Herbicide Resistance ◽

Palmer Amaranth ◽

High Genetic Diversity ◽

Widespread Occurrence ◽

Common Lambsquarters ◽

Herbicide Resistant ◽

Giant Ragweed

Abstract Pollen-mediated gene flow (PMGF) refers to the transfer of genetic information (alleles) from one plant to another compatible plant. With the evolution of herbicide-resistant (HR) weeds, PMGF plays an important role in the transfer of resistance alleles from HR to susceptible weeds; however, little attention is given to this topic. The objective of this work was to review reproductive biology, PMGF studies, and interspecific hybridization, as well as potential for herbicide resistance alleles to transfer in the economically important broadleaf weeds including common lambsquarters, giant ragweed, horseweed, kochia, Palmer amaranth, and waterhemp. The PMGF studies involving these species reveal that transfer of herbicide resistance alleles routinely occurs under field conditions and is influenced by several factors, such as reproductive biology, environment, and production practices. Interspecific hybridization studies within Amaranthus and Ambrosia spp. show that herbicide resistance allele transfer is possible between species of the same genus but at relatively low levels. The widespread occurrence of HR weed populations and high genetic diversity is at least partly due to PMGF, particularly in dioecious species such as Palmer amaranth and waterhemp compared with monoecious species such as common lambsquarters and horseweed. Prolific pollen production in giant ragweed contributes to PMGF. Kochia, a wind-pollinated species can efficiently disseminate herbicide resistance alleles via both PMGF and tumbleweed seed dispersal, resulting in widespread occurrence of multiple HR kochia populations. The findings from this review verify that intra- and interspecific gene flow can occur and, even at a low rate, could contribute to the rapid spread of herbicide resistance alleles. More research is needed to determine the role of PMGF in transferring multiple herbicide resistance alleles at the landscape level.

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Transfer of resistance alleles from herbicide-resistant to susceptible grass weeds via pollen-mediated gene flow

Weed Technology ◽

10.1017/wet.2021.82 ◽

2021 ◽

pp. 1-51

Author(s):

Amit J. Jhala ◽

Hugh J. Beckie ◽

Carol Mallory-Smith ◽

Marie Jasieniuk ◽

Roberto Busi ◽

...

Keyword(s):

Gene Flow ◽

Herbicide Resistance ◽

Creeping Bentgrass ◽

Agricultural Landscapes ◽

Italian Ryegrass ◽

Weed Species ◽

Herbicide Resistant ◽

Wild Oats ◽

Rigid Ryegrass ◽

Grass Weed

Abstract The objective of this paper was to review the reproductive biology, herbicide-resistant (HR) biotypes, pollen-mediated gene flow (PMGF), and potential for transfer of alleles from HR to susceptible grass weeds including barnyardgrass, creeping bentgrass, Italian ryegrass, johnsongrass, rigid (annual) ryegrass, and wild oats. The widespread occurrence of HR grass weeds is at least partly due to PMGF, particularly in obligate outcrossing species such as rigid ryegrass. Creeping bentgrass, a wind-pollinated turfgrass species, can efficiently disseminate herbicide resistance alleles via PMGF and movement of seeds and stolons. The genus Agrostis contains about 200 species, many of which are sexually compatible and produce naturally occurring hybrids as well as producing hybrids with species in the genus Polypogon. The self-incompatibility, extremely high outcrossing rate, and wind pollination in Italian ryegrass clearly point to PMGF as a major mechanism by which herbicide resistance alleles can spread across agricultural landscapes, resulting in abundant genetic variation within populations and low genetic differentiation among populations. Italian ryegrass can readily hybridize with perennial ryegrass and rigid ryegrass due to their similarity in chromosome numbers (2n=14), resulting in interspecific gene exchange. Johnsongrass, barnyardgrass, and wild oats are self-pollinated species, so the potential for PMGF is relatively low and limited to short distances; however, seeds can easily shatter upon maturity before crop harvest, leading to wider dispersal. The occurrence of PMGF in reviewed grass weed species, even at a low rate is greater than that of spontaneous mutations conferring herbicide resistance in weeds and thus can contribute to the spread of herbicide resistance alleles. This review indicates that the transfer of herbicide resistance alleles occurs under field conditions at varying levels depending on the grass weed species.

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Modeling gene flow from genetically modified plants.

10.1079/9781789247480.0007 ◽

2021 ◽

pp. 103-117

Author(s):

Wei Wei ◽

Jun-Ming Wang ◽

Xiang-Cheng Mi ◽

Yan-Da Li ◽

Yan-Ming Zhu

Keyword(s):

Gene Flow ◽

Genetically Modified ◽

Predictive Ability ◽

Crop Wild Relatives ◽

Gm Crops ◽

Wild Plants ◽

Experimental Conditions ◽

Flow Models ◽

Herbicide Resistant ◽

Gm Plants

Abstract Gene flow from genetically modified (GM) plants is concerning because of its ecological risks. In modeling studies, these risks may be reduced by altering crop management while taking environmental conditions into account. Gene flow modeling should consider many field aspects, both biological and physical. For example, empirical statistical models deduced from experimental data simulate gene flow well only under limited conditions (similar to experimental conditions). Mechanistic models, however, offer a potentially greater predictive ability. Gene flow models from GM crops to non-GM crops are used to simulate field conditions and minimize the adventitious presence of transgenes to meet certain threshold levels. These models can be adapted to simulate gene flow from GM crops to crop wild relatives using parameters of sexual compatibility and growth characteristics of the wild plants. Currently, modeling gene flow from herbicide-resistant weeds has become very important in light of the increased application of herbicides and widely evolved resistance in weeds.

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Assessing environmental impact of pollen-mediated transgene flow.

10.1079/9781789247480.0001 ◽

2021 ◽

pp. 1-25

Author(s):

Bao-Rong Lu

Keyword(s):

Gene Flow ◽

Environmental Impact ◽

Case Studies ◽

Environmental Impacts ◽

Genetically Engineered ◽

Weedy Rice ◽

Fitness Effect ◽

Trade Disputes ◽

Transgene Flow

Abstract Potential environmental impact caused by pollen-mediated transgene flow from commercially cultivated genetically engineered (GE) crops to their non-GE crop counterparts and to their wild and weedy relatives has aroused tremendous biosafety concerns worldwide. This chapter provides information on the concept and classification of gene flow, the framework of the environmental biosafety assessment caused by pollen-mediated gene flow, and relevant case studies about transgene flow and its environmental impact. In general, gene flow refers to the movement of genes or genetic materials from a plant population to other populations. Crop-to- crop transgene flow at a considerable frequency may result in transgene 'contamination' of non-GE crops, causing potential food/feed biosafety problems and regional or international trade disputes. Crop-to- wild/weedy transgene flow may bring about environmental impacts, such as creating more invasive weeds, threatening local populations of wild relative species, or affecting genetic diversity of wild relatives, if the incorporated transgene can normally express in the recipient wild/weedy plants and significantly alter the fitness of the wild/weedy plants and populations. It is therefore necessary to establish a proper protocol to assess the potential environmental impacts caused by transgene flow. Three steps are important for assessing potential environment impacts of transgene flow to wild/weedy relatives: (i) to accurately measure the frequencies of transgene flow: (ii) to determine the expression level of a transgene incorporated in wild/weedy populations; and (iii) to estimate the fitness effect (benefit or cost) conferred by expression of a transgene in wild/weedy populations. The recently reported case of non-random allele transmission into GE and non-GE hybrid lineages or experimental populations challenges the traditional method of estimating the fitness effect for the assessment of environmental impacts of transgene flow. Furthermore, case studies of transgenic mitigation (TM) strategies illustrate ways that may reduce the impacts of a transgene on wild/weedy populations if crop-to- wild/weedy transgene flow is not preventable, such as in the case of gene flow from crop rice to its co-occurring weedy rice.

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Gene flow from Clearfield® rice to weedy rice under field conditions

Plant Soil and Environment ◽

10.17221/616/2015-pse ◽

2016 ◽

Vol 62 (No. 1) ◽

pp. 16-22 ◽

Cited By ~ 7

Author(s):

Engku AK ◽

M. Norida ◽

Juraimi AS ◽

Rafii MY ◽

Abdullah SNA ◽

...

Keyword(s):

Gene Flow ◽

Field Conditions ◽

Weedy Rice

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Pollen-Mediated Gene Flow of Sulfonylurea-Resistant Kochia (Kochia scoparia)

Weed Science ◽

10.1017/s0043174500080887 ◽

1995 ◽

Vol 43 (1) ◽

pp. 95-102 ◽

Cited By ~ 60

Author(s):

George P. Stallings ◽

Donald C. Thill ◽

Carol A. Mallory-Smith ◽

Bahman Shafii

Keyword(s):

Gene Flow ◽

Soil Temperature ◽

Wind Direction ◽

Spring Barley ◽

Growing Season ◽

Sulfonylurea Herbicide ◽

Kochia Scoparia ◽

Herbicide Resistant ◽

Resistant Trait ◽

Plot Design

The movement of sulfonylurea herbicide-resistant (R) kochia pollen was investigated in a spring barley field near Moscow, ID, using a Nelder plot design in 1991 and 1992. Each 61 m diameter plot had 16 rays spaced 22.5° apart and contained 211 kochia plants. There were 12 susceptible (S) plants and one R plant along each ray. The R and S plants were 1.5 m and 3.0 to 30.5 m from the center of the plot, respectively. Wind direction and speed in the 16 vectors, air and soil temperature, and rainfall were monitored continuously. Mature kochia seed was collected from individual plants, planted in the greenhouse, and sprayed with chlorsulfuron to test for resistant F1progeny. Results from the 2-yr study showed outcrossing of R pollen onto S plants at rates up to 13.1% per plant 1.5 m from the R plants and declining to 1.4% per plant or less 29 m from the R plants. At least 35% of the total R x S crosses occurred in the direction of prevailing southeastward winds. Predicted percentages of R x S crosses per plant ranged from 0.16 to 1.29 at 1.5 m, and 0.00 to 0.06% at 29 m. Thus, resistant kochia pollen can spread the sulfonylurea-resistant trait at least 30 m during each growing season.

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