Robert Shell Track1, Maria Erickson2, Steve Hanlin2, Mark Millard2, Carolyn Lawrence3, 4, and Candice Gardner2
1 Cannon Ball, ND
2 USDA-ARS-PIRU, and North Central Regional Plant Introduction Station, Department of Agronomy, Iowa State University, Ames, IA
3 Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA
4 USDA-ARS, CICGRU, Ames, IA
Germplasm conservation is the safekeeping of the genetic diversity of a crop and its related species. In learning more about germplasm conservation this summer, I collected data, managed plant pollinators, grew plants from seed as a part of viability testing, and entered data into a database repository called GRIN (the Germplasm Resources Information Network). Although the plant pollinator work was carried out with various plants, the rest of the work focused mainly on maize (Zea mays L. subsp. mays, also called corn). In learning about corn, I tested germination rates for various accessions and entered data, and helped with hand pollination. Controlling pollination and testing seed viability and vigor are just some aspects of what is required to maintain maize germplasm.
The purpose of this project was to gain an understanding of maize germplasm conservation and its impact and to gain experience with methods used in germplasm conservation.
Harvested corn seeds can be stored for 20 to 30 years, and must be tested for viability to find out whether an increase in the seed stock should be scheduled. Seed are tested on a 5 to 10 year basis to make sure accessions do not expire before the expected 20 to 30 years. Increases are accomplished by planting the corn, then controlling the pollination so that the accessions are not contaminated by pollen from neighboring plants. In addition, because the corn was originally selected from a variety of different environments, there can be problems with increases for some accessions due to lack of adaptation. For example, the Southwest maize collection was collected in the Four Corners area, which is quite dry. Growing those accessions in Ames, Iowa, is quite difficult given their susceptibility to mold in the relatively wet climate of the Midwest. Once the crosses are made and the ears are harvested, phenotypic descriptions are created and entered into GRIN. In summary, germplasm conservation has many steps.
This work was done at the North Central Regional Plant Introduction Station (NCRPIS) in Ames, Iowa. The mission of the NCRPIS is to collect, maintain, and make available seeds from their collection to researchers and educators all over the world. NCRPIS has a diverse collection of maize, cucurbits, sunflower, flax and others. The number of maize seeds distributed is normally 100 kernels, but is increased from 100 to 200 kernels when germination falls to the 50-84% range. Distribution stops completely when germination falls below 50%. To ensure there is a supply of viable seed, there are important steps to be taken, some of which are described in this paper.
Methods and Materials
Different types of maize seeds from the germplasm collection were selected and tested in four replicates of 50 per seed lot totaling 200 seeds for each type. The seed were then taken out of each pouch and placed onto wet paper towels, folded up tightly and placed into tubs and then into a germinator set at 20 °C (12 hours dark), 30 °C (12 hours light) for 7 days. The towel tests were taken out on day 7 and seedlings were evaluated on how well the seeds germinated and grew (Figures 1 and 2). The seedlings were scored as to whether they were normal, abnormal or dead according to rules of the Association of Official Seed Analysts (AOSA, 2005). Those counts were then entered in the database, GRIN (Figure 3). GRIN tracks all the data about the seeds and that information is accessed by the Curators to study and make determinations as to when to increase seed in order to maintain an adequate and viable germplasm stock in storage.
Some plant species utilize insect pollinators to accomplish fertilization. Seed increase and production are improved when the insect chosen for use as a pollinator is compatible with the plant’s reproductive system. There are six types of insects used for pollination at the NCRPIS: honeybees, osmia bees, bumble bees, flies (house and blue bottle) and alfalfa leafcutters (ALC). All insect pollination at the NCRPIS is controlled by physically separating the accessions being increased and by containing the insect pollinators in the same cages that physically separate the different accessions.
When the germination tests were evaluated, approximately 10% to 15% of the seedlings were abnormal or did not grow (Figures 1 and 2). That gave the curators the information they needed to find out the relative viability of those seedlots under the seed storage conditions.
The objective of this project has been accomplished. I gained understanding of the study and work of maize germplasm conservation and its impact. I’ve studied and worked with employees at the NCRPIS and collected data. It was a great summer to spend with the GWC Internship and everyone else who was involved with this project.
My name is Robert Shell Track. I am from North Dakota on the Standing Rock Sioux Tribe Reservation, Cannon Ball. I am part Navajo and part Sioux. I grew up on Sioux territory, raised by my (Sioux) father. I came to this program to get a college experience for my upcoming college years. I learned about the GWC program from people at a nearby college, Sitting Bull College, in North Dakota.
Lisa Burke: NCRPIS, Biological Science Technician, Plants
Joan Peterson: Department of Agronomy
George Washington Carver
Mary de Baca: Program Advisor, Director of Diversity Programs
Dustin Thunder Hawk: Graduate Student, Assistant R.A.
Aurelio Curbelo: Program Assistant, Graduate Student, Assistant R.A.
Krystal Vasquez: Graduate Student, Assistant R.A.
Marcus Glenn: Graduate Student, Assistant R.A.
AOSA (2005) Association of Official Seed Analysts, Inc. Rules for Testing Seeds, Stillwater, OK. pp 89-92.
Figure 1. Germination testing: corn seedlings after 7days in the growth chamber.
Figure 2. Germination testing: Checking the seedling roots to see if they are healthy or diseased.
Figure 3. GRIN spreadsheet for data entry.