Introduction to Resistance Genetics: Traits

Amy Hauver Author

07/19/2022 Added

22 Plays

Description

You'll learn the genetic basis for resistance genetics through the example of herbicide resistant Palmer amaranth. This video describes genes, trait expression, and traits.

Searchable Transcript

Search:

[00:00:07.800]This video will act as an introduction
[00:00:10.110]to pesticide resistance genetics.
[00:00:17.310]Palmer amaranth is a common weed in agriculture
[00:00:20.070]and an important weed when discussing herbicide resistance.
[00:00:24.150]Glyphosate resistance in Palmer was first reported
[00:00:27.000]in the United States in the state of Georgia in 2014
[00:00:31.260]and has since emerged in different states
[00:00:33.300]throughout the Midwest.
[00:00:36.120]So how does resistance to pesticides
[00:00:38.610]like Palmer amaranth's resistance to glyphosate develop?
[00:00:43.050]Organisms have different traits
[00:00:44.820]like the height of the Palmer plant in this image.
[00:00:47.790]And they are expressed and can be selected for
[00:00:49.650]in suitable environments.
[00:00:52.050]To begin to understand development of herbicide resistance,
[00:00:55.050]we need to understand traits
[00:00:56.490]and how they express themselves in plants.
[00:01:00.720]Traits are characteristics or features controlled
[00:01:04.170]by genes that can be passed from one generation to another.
[00:01:08.130]Some examples are the height of individual plants,
[00:01:11.820]the flower colors of soybeans, or the ability of a plant
[00:01:15.210]to tolerate herbicides, like Palmer's resistance
[00:01:18.150]to glyphosate being controlled
[00:01:20.010]by the EPS synthase expression.
[00:01:23.190]Traits are genetic factors
[00:01:24.840]that predetermine certain characteristics about a plant,
[00:01:29.520]but there are outside factors
[00:01:31.080]that influence that plant as well,
[00:01:32.790]like the amount of nutrients or water it receives.
[00:01:36.540]The genes controlling
[00:01:37.560]the genetic factor of traits are encoded in DNA,
[00:01:41.700]or deoxyribose nucleic acid.
[00:01:44.190]So let's take a closer look.
[00:01:46.800]Continuing with our example,
[00:01:48.390]let's look at this Palmer plant.
[00:01:50.070]In order to look at its DNA
[00:01:51.750]we need to take an even closer look
[00:01:53.310]at its leaf and its cellular makeup.
[00:01:57.660]Palmer leaves are made up of millions of cells,
[00:02:00.180]each holding a nucleus which contains the chromosomes.
[00:02:03.840]Chromosomes are made up of DNA,
[00:02:06.360]the genetic material in all living things.
[00:02:09.510]Genes are segments of DNA that encode for specific proteins.
[00:02:13.950]Following the polymer example, on this chromosome
[00:02:16.890]the EPSP synthase gene is shown.
[00:02:19.710]Typically one gene is present,
[00:02:21.690]so when glyphosate is applied
[00:02:23.550]it renders the EPSP synthase inoperable.
[00:02:27.810]This paper details the molecular process
[00:02:30.030]by which Palmer amaranth is able
[00:02:31.740]to tolerate applications of glyphosate.
[00:02:34.710]The authors attribute glyphosate resistance
[00:02:36.870]in Palmer amaranth to gene amplification.
[00:02:40.200]Since there is originally only one EPSP synthase gene,
[00:02:44.220]Palmer was controlled easily by glyphosate applications.
[00:02:47.640]Over time and through selection,
[00:02:49.620]Palmer plants with more than one copy
[00:02:51.510]of the EPSP synthase gene became more prevalent
[00:02:54.390]in the population.
[00:02:56.880]The amplification of EPSP synthase genes is responsible
[00:03:00.780]for the glyphosate resistance trait.
[00:03:03.210]Massive overproduction of EPSP synthase
[00:03:06.030]produced by the additional EPSPS gene
[00:03:10.470]allows the plant to cope despite the presence of glyphosate,
[00:03:14.040]essentially acting as a molecular sponge
[00:03:16.170]to soak up the herbicide and allow the plant to survive.
[00:03:20.400]Having different traits means
[00:03:21.720]that there are some individuals that will thrive better
[00:03:23.910]to different environments.
[00:03:25.770]Like Palmer amaranth with glyphosate,
[00:03:27.720]some plants have traits that allow them
[00:03:29.370]to tolerate certain herbicides.
[00:03:31.590]Palmer's high reproductive rates
[00:03:33.210]and its ability to build a large population
[00:03:35.670]makes it difficult to manage and contributes
[00:03:37.710]to the development of resistance.
[00:03:40.860]Traits may only be visible
[00:03:42.390]if they're influenced by the environment.
[00:03:44.580]In the case of this Palmer amaranth,
[00:03:46.260]you can't see that it's a glyphosate-resistant plant
[00:03:48.870]because you cannot see its genes.
[00:03:51.090]But if you take a close look,
[00:03:52.560]you will see that this individual plant carries
[00:03:54.690]extra copies of the EPSP synthase genes
[00:03:57.870]that will make it glyphosate resistance.
[00:04:00.810]Once the environment changes,
[00:04:02.610]like glyphosate being applied by a farmer,
[00:04:05.040]you would be able to see the herbicide resistance trait.
[00:04:08.220]If the Palmer carries the amplified EPSPS genes,
[00:04:12.240]then it is fully resistant
[00:04:14.040]to the herbicide and will survive.
[00:04:16.410]If it only carries half of that amplified amount,
[00:04:18.870]it may be injured, but could still survive an application.
[00:04:22.680]If it carries the single EPSP synthase gene,
[00:04:25.830]then it is fully susceptible and will likely die.
[00:04:29.700]Under certain circumstances, traits like Palmer resistance
[00:04:33.210]to glyphosate can be selected for within a population.
[00:04:36.540]In this case, it would be herbicide applications.
[00:04:39.900]In the case of Palmer,
[00:04:41.220]large populations have a diverse gene pool
[00:04:43.590]with different traits that may be selected for,
[00:04:46.050]which can lead to a higher chance of resistance developing.
[00:04:49.950]Individuals that have these traits survive
[00:04:52.140]and become more prevalent in the population.
[00:04:54.810]As Palmer plants with resistance traits are selected,
[00:04:57.900]they're able to survive
[00:04:59.040]glyphosate application and reproduce.
[00:05:01.560]This increases the frequency
[00:05:02.880]of the resistance traits in the population.
[00:05:07.230]Weed biologists are utilizing tools
[00:05:09.750]of molecular genetics to uncover the genetic basis
[00:05:12.540]for the herbicide resistance traits observed in the field,
[00:05:16.020]like Palmer amaranth resistance to glyphosate
[00:05:18.360]being influenced by gene amplification.
[00:05:21.720]In summary, resistance to pesticides comes
[00:05:24.300]from traits in individuals that are expressed.
[00:05:27.180]These traits allow them to tolerate certain herbicides,
[00:05:29.730]like Palmer with glyphosate.
[00:05:31.680]Under certain environments these traits can be selected for
[00:05:34.170]in the population, like a herbicide application
[00:05:37.020]killing all glyphosate-susceptible Palmer plants
[00:05:40.050]and leaving the resistant plants to reproduce.
[00:05:42.870]These individuals with resistance traits
[00:05:45.180]become more prevalent in the population
[00:05:46.980]as they reproduce, leading to a resistance population.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Introduction to Resistance Genetics: Traits

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments