Identifying patterns of heredity for cytoplasmic male sterility in Brassica rapa

Jaqueline Korth and Cambelle Johnson Author

04/05/2021 Added

3 Plays

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The project involves screening Wisconsin fast plants for the CMS phenotype to track their heredity.

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[00:00:00.370]Hello, my name is Jacquelyn Korth
[00:00:02.680]and I am a junior biological sciences student
[00:00:06.700]at the University of Nebraska-Lincoln.
[00:00:09.190]My UCARE project this year was done
[00:00:12.140]as a partner project with Cambelle Johnson,
[00:00:15.410]and this was in Dr. Christensen's lab.
[00:00:20.180]Our project was identifying patterns of heredity
[00:00:23.530]for cytoplasmic male sterility
[00:00:25.580]in the species Brassica rapa.
[00:00:29.330]Our UCARE project focused on cytoplasmic male sterility.
[00:00:34.040]Cytoplasmic male sterility is the inability of a plant
[00:00:37.540]to produce functional pollen grains.
[00:00:40.410]This phenotype is prized in agriculture and horticulture
[00:00:43.930]for its uses in crossbreeding crop plants
[00:00:46.410]without genetic modification.
[00:00:49.320]CMS is a trait that is naturally occurring in many species,
[00:00:52.820]but is rare in the wild.
[00:00:55.580]The plant we used for this project,
[00:00:57.860]Wisconsin Fast Plants, are a cultivar of Brassica rapa
[00:01:01.850]and provided a model organism for our research.
[00:01:05.570]On the right of this slide in figure one
[00:01:08.750]is a photo of a male sterile flower without anthers.
[00:01:14.840]Anthers are where the pollen is located within a flower.
[00:01:19.500]In the second figure, there is a normal flower
[00:01:23.850]with functional pollen.
[00:01:27.460]This is a very good indicator of the CMS phenotype.
[00:01:33.290]The hypothesis guiding our research
[00:01:35.610]is that rare random mutations that cause CMS
[00:01:39.590]are naturally occurring,
[00:01:41.520]and because CMS is a maternally inherited phenotype,
[00:01:45.920]the phenotype will increase in frequency
[00:01:48.300]when it is selected for.
[00:01:51.680]To test our hypothesis,
[00:01:53.300]we decided to examine our chosen cultivar of Brassica rapa
[00:01:57.900]for naturally occurring male sterile flowers
[00:02:00.500]in order to understand
[00:02:02.270]how often the phenotype occurred naturally.
[00:02:05.580]Additionally, we decided to pollinate
[00:02:07.870]all male sterile flowers found
[00:02:09.750]during the screening process in order to see
[00:02:12.700]if the phenotype is heritable in the next generation.
[00:02:18.453][Cambelle Johnson] First off,
[00:02:19.286]I'd like to introduce myself.
[00:02:21.090]I am Cambelle Johnson.
[00:02:22.760]I will be going through the next few slides.
[00:02:26.060]The data collection process for this project
[00:02:28.780]involved physically screening the Wisconsin Fast Plants
[00:02:31.970]for the CMS phenotype.
[00:02:34.250]Once discovered, these flowers were tagged with tape
[00:02:37.260]and the parent plant was denoted on that tag,
[00:02:40.510]so in future it would be easy to track their heredity.
[00:02:44.440]That flower was then manually crossed with pollen
[00:02:47.210]from a fertile flower on another plant,
[00:02:50.030]and then those seeds were collected
[00:02:51.760]and stored in packets for the next generation.
[00:02:55.830]The first generation of plants had a surprisingly high rate
[00:02:59.440]of CMS considering the small sample size of 14,
[00:03:03.750]and the standard low-frequency seen in other populations.
[00:03:07.940]The base rate was found to be about 8.79 steriles per plant.
[00:03:13.300]In addition to this data, there's the discovery
[00:03:16.070]of Wis Fast 2, a fully male sterile mutant.
[00:03:20.370]These flowers were also pollinated to obtain seeds
[00:03:23.440]and track heredity in the next generation.
[00:03:30.580]The naturally occurring CMS phenotype
[00:03:34.140]was identified in Wisconsin Fast Plants.
[00:03:37.230]However, it remains to be seen
[00:03:38.950]whether the base frequency of sterility in this sample
[00:03:42.700]increases through subsequent generations
[00:03:45.420]and thus supports the hypothesis.
[00:03:47.930]The baseline frequency of the CMS phenotype was obtained
[00:03:51.500]from the parent generation,
[00:03:53.430]fulfilling the first project objective
[00:03:55.490]or OB1 denoted on the slide.
[00:03:58.430]The screening of the progeny of the CMS flowers
[00:04:01.790]will reveal the patterns in heredity
[00:04:04.050]in accordance with objective two.
[00:04:06.840]As most of the collective data will be obtained
[00:04:09.340]through analysis of future generations of Fast Plants,
[00:04:12.990]majority of the results of this project remain to be seen.
[00:04:16.950]Through the exploration of both future generations
[00:04:20.040]and Wis Fast 2 progeny, the heritable tendencies
[00:04:23.200]of the phenotype will be established.
[00:04:27.720]We would like to acknowledge our principal investigator,
[00:04:31.140]Dr. Alan Christensen in biological sciences
[00:04:34.500]and the undergraduate and graduate students in his lab.
[00:04:38.260]Special thanks to the director
[00:04:39.910]of undergraduate research, Justina Clark,
[00:04:42.200]for all her guidance,
[00:04:43.450]and all the UCARE staff for their support of this project.

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Identifying patterns of heredity for cytoplasmic male sterility in Brassica rapa

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