Influential Literature: Gene Transfer and Pollen Movements
Citespace is a visualization tool that allows one to see trends in scientific literature. Using this tool we determined the most pivotal article for Genetically Modified foods and the sub-topics, or clusters, that are affiliated with it. Here is the link to the website: Citespace
Pivotal Article
"Pollen-Mediated Movement of Herbicide Resistance Between Commercial Canola Fields" was a study done in Australia and was published in June 2002. The study focused on genetically modified Brassica napus, more commonly known as Canola, that was herbicide resistant. Specifically, the pollen movement between the genetically modified Canola and other non-genetically modified crops was analyzed to determine whether it could cause "genetic pollution of the environment."
The GM Canola is resistant to acetolactate synthase (ALS) which makes it resistant to herbicides. Each chromosome contains one herbicide resistant gene, both of which are homozygous. This means that in cross pollination, it is likely that the non-GM crop will contain one copy of each gene. The question is, will that mean that it will become resistant?
The study showed that only 30% of the samples tested turned out to be herbicide resistant. The results from the study indicate that gene flow does in fact occur between Canola fields through pollen movement up to 3km from a source site. However, gene flow is less than 1%, even in adjacent Canola fields. Also, the further away the field, the less likely there will be any gene flow. No resistance was found in fields more than 3 km from the source site.
This study is thought to be unique for several reasons. Unlike most studies of pollen movements which used small, artificial sites, this one was conducted on large commercial fields, used very large sample sizes and was "conducted over one-third of Australia" meaning that it covered a range of different environments. It was also unique because the results did not show any genetic pollution in the environment. This article has been influential primarily in studies done on gene flow and pollen movement, focusing specifically on the environmental impacts and potential consequences. Others have used this study as an example for studying pollen movement and gene flow by using larger scaled sites and more natural environments. They have also built upon concepts developed in the study.
Pivotal Article
"Pollen-Mediated Movement of Herbicide Resistance Between Commercial Canola Fields" was a study done in Australia and was published in June 2002. The study focused on genetically modified Brassica napus, more commonly known as Canola, that was herbicide resistant. Specifically, the pollen movement between the genetically modified Canola and other non-genetically modified crops was analyzed to determine whether it could cause "genetic pollution of the environment."
The GM Canola is resistant to acetolactate synthase (ALS) which makes it resistant to herbicides. Each chromosome contains one herbicide resistant gene, both of which are homozygous. This means that in cross pollination, it is likely that the non-GM crop will contain one copy of each gene. The question is, will that mean that it will become resistant?
The study showed that only 30% of the samples tested turned out to be herbicide resistant. The results from the study indicate that gene flow does in fact occur between Canola fields through pollen movement up to 3km from a source site. However, gene flow is less than 1%, even in adjacent Canola fields. Also, the further away the field, the less likely there will be any gene flow. No resistance was found in fields more than 3 km from the source site.
This study is thought to be unique for several reasons. Unlike most studies of pollen movements which used small, artificial sites, this one was conducted on large commercial fields, used very large sample sizes and was "conducted over one-third of Australia" meaning that it covered a range of different environments. It was also unique because the results did not show any genetic pollution in the environment. This article has been influential primarily in studies done on gene flow and pollen movement, focusing specifically on the environmental impacts and potential consequences. Others have used this study as an example for studying pollen movement and gene flow by using larger scaled sites and more natural environments. They have also built upon concepts developed in the study.
Clusters
Oilseed rape
Upon using the Citespace map to determine the most pivotal article for Genetically Modified foods, we discovered a few clusters of articles that are directly affiliated with the main article about pollen movements and gene flow. This article describes the environmental consequences associated with GM crops and their potential cross-pollination effects, and relates also to the potential health risks which our controversy encompasses.
There are two main clusters from the Citespace map - a blue cluster and a yellow cluster - which feature articles that either focus on slightly different aspects of GM foods or are also related to the topics of gene flow and pollen movements. The blue cluster features articles which discuss gene flow, some more specifically referring to North American crops. According to one study, the Bacillus thuringiensis (Bt) gene added to wild sunflowers resulted in an unexpectedly large increase in seed production and implied that some genes could exacerbate weed growth (Snow, 2002). Another study which focused on cultivated rice also discussed gene flow and the potential associated risks as a result of out-crossing. The methods used in this study were experiments conducted in Korea and China to determine gene flow from cultivated rice to weedy rice, in addition to herbicide resistance and SSR molecular finger printing to predict gene flow frequencies (Chen et. al, 2003).
The yellow cluster features articles that focus mainly on pollen movements. In one study, a pollen dispersal experiment was conducted with herbicide-resistant transgenic oilseed rape by measuring the pollen dispersal from the entire source plot and then determining the distribution of pollen from a single plant through two different methods (Lavigne et. al, 1998). Their findings suggest that individual plants should be considered rather than entire plots because that tends to underestimate pollen dispersal. Another article in this cluster also focuses on pollen, but more specifically assessing the risks of pollen-mediated gene flow for oilseed rape (Walklate et. al, 2004). This assessment was conducted through the usage of a mathematical model for predicting spatial distribution of pollen dispersal and pollination (much like the previous study) but also includes the variables of wind and insect activity. Their findings suggest that target-crop fertility and source-crop size are the most important factors, and that the idea of isolation distance would only be useful for self-fertile target crops (Walklate et. al, 2004).
These questions are precipitating much of the debate among researchers because the extent of what negative effects GM crops have on the environment as well as human health are still uncertain. If GM crops are able to become resistant to herbicides, who's to say this couldn't also happen to weeds as well? And if GM crops spread their genes to their wild and weedy relatives through cross-pollination, could this potentially create stronger and more resistant weeds and insects that we are unable to exterminate?
There are two main clusters from the Citespace map - a blue cluster and a yellow cluster - which feature articles that either focus on slightly different aspects of GM foods or are also related to the topics of gene flow and pollen movements. The blue cluster features articles which discuss gene flow, some more specifically referring to North American crops. According to one study, the Bacillus thuringiensis (Bt) gene added to wild sunflowers resulted in an unexpectedly large increase in seed production and implied that some genes could exacerbate weed growth (Snow, 2002). Another study which focused on cultivated rice also discussed gene flow and the potential associated risks as a result of out-crossing. The methods used in this study were experiments conducted in Korea and China to determine gene flow from cultivated rice to weedy rice, in addition to herbicide resistance and SSR molecular finger printing to predict gene flow frequencies (Chen et. al, 2003).
The yellow cluster features articles that focus mainly on pollen movements. In one study, a pollen dispersal experiment was conducted with herbicide-resistant transgenic oilseed rape by measuring the pollen dispersal from the entire source plot and then determining the distribution of pollen from a single plant through two different methods (Lavigne et. al, 1998). Their findings suggest that individual plants should be considered rather than entire plots because that tends to underestimate pollen dispersal. Another article in this cluster also focuses on pollen, but more specifically assessing the risks of pollen-mediated gene flow for oilseed rape (Walklate et. al, 2004). This assessment was conducted through the usage of a mathematical model for predicting spatial distribution of pollen dispersal and pollination (much like the previous study) but also includes the variables of wind and insect activity. Their findings suggest that target-crop fertility and source-crop size are the most important factors, and that the idea of isolation distance would only be useful for self-fertile target crops (Walklate et. al, 2004).
These questions are precipitating much of the debate among researchers because the extent of what negative effects GM crops have on the environment as well as human health are still uncertain. If GM crops are able to become resistant to herbicides, who's to say this couldn't also happen to weeds as well? And if GM crops spread their genes to their wild and weedy relatives through cross-pollination, could this potentially create stronger and more resistant weeds and insects that we are unable to exterminate?
Sources:
Chen, L. (2004). Gene flow from cultivated rice (Oryza sativa) to its weedy and wild relatives. Annals of Botany, 93: 67-73.
Lavigne, C. (1998). A pollen-dispersal experiment with transgenic oilseed rape. Estimation of the average pollen dispersal of an individual plant within a field. Theor Appl Genet, 96: 886-896.
Reiger, M., Lamond, M., Preston, C., Powles, S., Roush, R. (2002). Pollen-Mediated Movement of Herbicide Resistance Between Commercial Canola Fields. Science, 296: 2386-2388.
Snow, A. (2002). Transgenic crops - Why gene flow matters. Nature Biotechnology, 20: 542.
Walklate, P.J. (2004). A model of pollen-mediated gene flow for oilseed rape. Proc. R. Soc. Lond. B: 271, 441-449.
Chen, L. (2004). Gene flow from cultivated rice (Oryza sativa) to its weedy and wild relatives. Annals of Botany, 93: 67-73.
Lavigne, C. (1998). A pollen-dispersal experiment with transgenic oilseed rape. Estimation of the average pollen dispersal of an individual plant within a field. Theor Appl Genet, 96: 886-896.
Reiger, M., Lamond, M., Preston, C., Powles, S., Roush, R. (2002). Pollen-Mediated Movement of Herbicide Resistance Between Commercial Canola Fields. Science, 296: 2386-2388.
Snow, A. (2002). Transgenic crops - Why gene flow matters. Nature Biotechnology, 20: 542.
Walklate, P.J. (2004). A model of pollen-mediated gene flow for oilseed rape. Proc. R. Soc. Lond. B: 271, 441-449.
