Breeding Overview

Grace Troupe, Presenter Author

10/11/2018 Added

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After a soybean plant has gone through plant transformation and contains the new transgene, the process of genetic engineering is still far from over! This plant must be backcrossed to an elite variety to move the gene into soybeans that farmers want to grow. Watch this video to get an overview of that process.

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[00:00:06.410]Now that you finished the third step
[00:00:07.860]of genetic engineering,
[00:00:09.370]let's see where we are in the journey of this gene
[00:00:12.150]and do an overview of the breeding process.
[00:00:15.310]So, we started in the lab of Madan
[00:00:17.050]who's the transgene designer.
[00:00:18.480]He put a soybean promoter
[00:00:20.100]with an Arabidopsis coding region
[00:00:22.250]to make the transgene so he would have an SDS-resistant gene
[00:00:26.040]that's turned on in soybean roots.
[00:00:28.450]He then sent this transgene over in a test tube
[00:00:31.070]to Shirley in the plant transformation facility
[00:00:34.270]and she got this transgene into soybean plants.
[00:00:38.750]Shirley then sent these plants with the transgene
[00:00:42.090]over to George who then worked on breeding them
[00:00:44.910]with elite varieties.
[00:00:47.270]So, let's take a look at this process.
[00:00:50.280]George's goal was to breed this transgene
[00:00:53.160]into elite soybean varieties.
[00:00:56.260]And we'll talk about what we mean by elite soybean varieties
[00:00:59.050]in just a second.
[00:01:01.230]But my first question is why can't we just use the plants
[00:01:04.569]that Shirley made, those transformed plants?
[00:01:07.520]That gene is in a soybean plant, right?
[00:01:10.180]So, why do we do this breeding process?
[00:01:12.990]That's where the elite varieties come in.
[00:01:15.770]So, the types of soybean varieties
[00:01:17.940]that Shirley uses are really good
[00:01:20.560]at making it through this Petri dish process,
[00:01:23.540]at growing in these Petri dishes
[00:01:25.640]and accepting the transgene
[00:01:27.610]and working with the Agrobacterium,
[00:01:29.320]so she uses specialized varieties
[00:01:31.040]that work really well in that system
[00:01:33.490]but these varieties aren't the ones
[00:01:36.310]that the farmers are wanting to buy,
[00:01:38.400]they're not producing the most soybeans
[00:01:40.340]and they don't have all the latest traits
[00:01:43.460]but elite varieties do.
[00:01:44.840]These are the latest and greatest ones
[00:01:46.730]that farmers really wanna plant.
[00:01:48.840]So, what has to happen
[00:01:50.640]is once these soybeans get this transgene in it,
[00:01:54.827]it's easy for us to breed that transgene
[00:01:58.280]into these soybean plants
[00:02:00.090]that are the latest and greatest.
[00:02:02.070]So, we have this intermediate step
[00:02:04.180]where we get the transgene in
[00:02:05.900]but then we have to move it over
[00:02:07.210]to what farmers actually wanna grow
[00:02:09.470]and those are those elite varieties.
[00:02:12.630]Now that we've laid that framework,
[00:02:14.187]we can go back and look at what this breeding process is.
[00:02:18.760]So, the goal is to breed that transgene
[00:02:21.060]into those elite varieties,
[00:02:24.270]so we have our soybean plant
[00:02:25.990]and we only wanna move over that transgene
[00:02:30.220]and soybean plants actually have about 50,000 genes,
[00:02:34.120]so we wanna maintain as many of the 50,000 elite genes
[00:02:39.420]as possible and only move over that transgene
[00:02:42.689]from the plants that Shirley sent over.
[00:02:48.950]So, how do we move this gene across?
[00:02:52.660]We have to do breeding.
[00:02:54.640]We have to make crosses,
[00:02:56.570]so pause this video and think
[00:02:58.790]what are these parts, these flower parts here
[00:03:01.750]that we're trying to bring together to make a cross?
[00:03:07.140]Up here we have the stamen,
[00:03:10.190]so that is made up of that filament and the anther
[00:03:13.080]and that anther's this tiny speck up here
[00:03:15.010]that has the pollen
[00:03:16.107]and we need to get this pollen
[00:03:18.360]on the stigma, that's part of the pistol here,
[00:03:23.570]the stigma is what accepts the pollen
[00:03:25.250]so you can make seed
[00:03:27.380]that's a cross between these two varieties.
[00:03:32.050]So, we need to have a plan
[00:03:33.730]for how we're gonna make these crosses
[00:03:35.820]and when we're doing this process
[00:03:39.200]in genetic engineering it's called backcross breeding.
[00:03:42.850]So, why's it called backcross breeding?
[00:03:44.580]What is that?
[00:03:46.860]It's because you keep crossing it back to one variety,
[00:03:49.710]that elite variety.
[00:03:51.280]You only use that transgenic plant from Shirley once
[00:03:54.940]and in the original cross where you cross it with elite,
[00:03:58.460]and then every generation after that,
[00:04:00.800]you try and keep crossing it back
[00:04:02.890]to that elite variety,
[00:04:04.340]this green one, you keep crossing it to that
[00:04:06.590]and every generation you'll keep the transgene,
[00:04:09.360]you can do DNA testing
[00:04:11.260]to make sure that you're keeping it
[00:04:15.290]but you're getting more and more of those elite genes,
[00:04:17.750]you're trying to get as close
[00:04:19.390]as getting 50,000 of those elite genes as possible
[00:04:23.740]but keeping that transgene,
[00:04:25.070]so in the end, you have an elite variety
[00:04:27.560]with the new transgene.
[00:04:29.950]So, again it's called backcross breeding
[00:04:31.560]'cause you keep crossing it back to one parent,
[00:04:34.950]one parent line.
[00:04:39.740]So, this whole process you can see
[00:04:41.550]uses a lot of generations.
[00:04:43.540]It takes about seven years to get through this
[00:04:47.390]and the plants are also tested
[00:04:49.610]in different field environments
[00:04:51.130]to make sure that these are really great
[00:04:53.580]and they're ready for farmers to grow
[00:04:55.810]and they'll perform how we expect them to.
[00:05:00.300]So, now we're at the end of this breeding process
[00:05:04.330]and now we'll learn about DNA testing.
[00:05:06.890]In reality, this happens kind of alongside of breeding
[00:05:11.890]but we separate it out as a different step
[00:05:14.110]so you can see all the different parts of DNA testing
[00:05:17.590]and learn it in detail
[00:05:19.100]but this kind of happens in conjunction with breeding.
[00:05:22.510]So, we'll see you in step four.

Breeding Overview

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Breeding Overview

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