Plant Germplasm Conservation
Robert Shell Track1, Maria Erickson2, Steve Hanlin2, Mark Millard2, Carolyn
Lawrence3, 4, and Candice Gardner2
1
Cannon Ball, ND
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
2
Abstract
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.
Introduction
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
Germination testing
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.
Insect Pollinators
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.
Results
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.
Conclusions
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.
About Me
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.
Acknowledgements
Mentors
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.
References
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.