Introduction of simple breeding concepts to students using an array of different maize varieties

Caleb Wehrbein Author

07/27/2020 Added

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An introductory video showing simple breeding concepts in maize varieties to provide insight into the fundamentals of maize breeding as well as providing students a hands-on experience.

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[00:00:00.000]Hello, my name is Caleb Wehrbein. I am a senior undergraduate here at
[00:00:04.087]the University of Nebraska - Lincoln, and today we'll
[00:00:07.117]look at a project that introduces simple breeding concepts
[00:00:10.140]to students using an abundance of maize varieties.
[00:00:22.930]Maize is a monecious plant with imperfect flowers
[00:00:26.530]meaning the male flowers and female flowers are
[00:00:29.510]separated from each other on the same plant.
[00:00:32.650]The male flowers, the tassels, are located at the top of
[00:00:36.400]the plant while the female flowers, the ears and silks,
[00:00:40.150]are located at nodes along the side of the plant
[00:00:43.496]when the tassels become reproductively mature, they
[00:00:46.448]begin to shed pollen which would normally fall on
[00:00:49.273]receptive silks, thus resulting in pollination.
[00:00:53.157]There are many different types of maize, such as
[00:00:55.987]different dent corns, flint corns, sweetcorns, and
[00:01:02.047]popcorns, each with their own commercial and industrial
[00:01:05.607]uses. Here at UNL, a maize breeding project was
[00:01:09.677]started to give students a hands-on perspective as to
[00:01:12.634]how a breeder in the industry would cross-pollinate
[00:01:15.137]different assortments of maize (each with their own
[00:01:17.907]desirable traits) to create a new variety.
[00:01:21.577]Set up in an early and late planting block pattern,
[00:01:24.355]roughly 40 varieties of different dent corns,
[00:01:27.225]flint corns, popcorns, and sweetcorns were planted
[00:01:31.037]in ranges. The great diversity of maize types chosen
[00:01:35.173]for this project offer a mixture of characteristics to select
[00:01:38.913]for when breeding, including differences in coloration,
[00:01:42.913]agronomic performance, presence of sugary sweetcorn
[00:01:46.253]mutations, and mutations that impart increased
[00:01:49.705]nutritional qualities such as those found in the
[00:01:52.395]high-lysine quality protein maize.
[00:01:55.252]The sugary1 mutation, or Su1 for short, was the
[00:01:59.309]first mutation discovered in sweetcorn variants and is
[00:02:03.202]known for slowing down the starch synthesis process
[00:02:07.032]giving kernels their slightly shrunken appearance.
[00:02:10.666]The shrunken2 mutation, or Sh2 for short, is another
[00:02:14.666]mutation found in sweetcorn that doesn't allow starch to
[00:02:18.222]be produced at all, contributing to severely shriveled
[00:02:21.563]kernels in comparison to Su1 mutants.
[00:02:27.303]This allows us to accomplish three different objectives
[00:02:30.236]during the study, which includes cross-pollinating
[00:02:33.086]various colored and sweetcorn varieties to create
[00:02:35.838]new, colorful, and exciting sweetcorns,
[00:02:39.980]cross-pollinating quality protein maizes with other
[00:02:43.050]sweetcorn variants to create a more nutritious
[00:02:46.237]sweetcorn, and cross-pollinating quality protein maizes
[00:02:50.352]with colored popcorn variants to create more
[00:02:52.860]nutritious and colorful popcorn varieties.
[00:02:56.932]It is to note that student involvement in the project
[00:02:59.571]this year has been limited due to health and safety
[00:03:02.114]concerns brought about by covid-19.
[00:03:08.212]The first step in preparing crosses between different
[00:03:11.312]varieties of maize starts by scanning the ranges early
[00:03:14.272]each day for emerging ears. If there are emerging
[00:03:18.212]ears appearing on the plant, the ear is quickly white
[00:03:21.059]capped by placing a small, water resistant bag over the
[00:03:24.081]ear. This prevents the ear from being pollinated from
[00:03:27.471]surrounding maize plants once the silks emerge
[00:03:30.274]since maize begins to shed pollen briefly after sunlight
[00:03:33.628]hits the tassel.
[00:03:36.718]Once the entire plot has been scanned for emerging
[00:03:39.663]ears, the next step in preparing crosses would be to
[00:03:42.613]identify tassels beginning to shed pollen. A quick
[00:03:46.021]way to check if the tassel is shedding pollen is by watching for
[00:03:49.491]open anthers hanging from the tassel as well as
[00:03:51.876]giving the tassel a few taps. If pollen is being shed, a
[00:03:55.876]labeled brown paper bag denoting the variety and date
[00:03:59.876]is placed over the tassels, folded at the bottom, and
[00:04:02.916]held together by a paper clip to collect pollen that will
[00:04:06.064]be shed the next morning. This ensures that the pollen
[00:04:10.064]collected is a fresh and pure sample of pollen shed
[00:04:13.284]from that specific plant since pollen shed from the
[00:04:16.174]previous day will have died off.
[00:04:20.423]On the following morning, after the plants have started
[00:04:23.443]shedding on mass and the bags are completely dry,
[00:04:26.073]the fresh pollen is collected by repeatedly slapping
[00:04:29.071]the brown paper bag and then pulling the bag off
[00:04:32.131]the tassel. The contents of the bag may include both dry
[00:04:36.131]anthers and pollen shed from the plant. Once the
[00:04:39.729]pollen is collected, another compatible plant that would
[00:04:42.959]produce offspring in line with our project's goals must
[00:04:46.469]be identified. In this demonstration, we are crossing
[00:04:50.019]Bloody Butcher pollen with the IA453 shrunken2 mutant
[00:04:55.399]female by spreading the pollen over the silks and
[00:04:59.219]quickly stapling the bag over the crossed ear.
[00:05:04.008]By crossing colored varieties such as the
[00:05:06.468]Bloody Butcher variety with parents used in
[00:05:09.226]sweetcorn hybrid production like the Golden Cross
[00:05:13.226]and Iowa Chief hybrid, we create parental lines
[00:05:17.226]that can be used to develop a colored, hybrid
[00:05:20.226]variety of sweetcorn boasting superior traits from
[00:05:23.656]from both parents from each respective cross.
[00:05:28.019]All of the crosses made from the parent material
[00:05:30.739]in the first year will result in the first crossed offspring
[00:05:34.739]also referred to as the F1 generation
[00:05:37.729]which we expect to be heterozygous for the traits
[00:05:40.485]crossed through Mendelian genetics. Going forward,
[00:05:44.845]in the coming years for the project, the F1 generation
[00:05:48.435]will be grown and self-pollinated to give rise to the
[00:05:51.129]F2 generation. It is in the F2 generation where we
[00:05:55.389]will observe the plants beginning to segregate
[00:05:58.360]phenotypically from the uniformity displayed in
[00:06:01.410]the F1 generation, giving rise to multiple plants with
[00:06:05.660]various combinations of traits
[00:06:08.420]which could be heterozygous at one locus while
[00:06:11.141]being homozygous at another. It is our hope
[00:06:14.715]that this study may achieve the goals of creating
[00:06:18.005]new, colorful sweetcorns, more nutritious sweetcorns
[00:06:22.384]and more nutritious popcorns in the coming years with
[00:06:26.384]the conclusion of the project.
[00:06:30.544]I'd like to thank Dr. Holding for his help in organizing
[00:06:33.543]and leading the project, Dr. Elowsky for assisting in
[00:06:36.473]organizing the project and providing material,
[00:06:39.513]Craig Chandler for help in collecting
[00:06:41.323]camera footage, Lydia Regier for help
[00:06:44.407]conducting crosses, and the UNL UCARE program for
[00:06:48.407]sponsorship. Thank you

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Introduction of simple breeding concepts to students using an array of different maize varieties

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