|
2008 RESEARCH
PAPERS AND POSTERS
Moderator: Jack Peters at
jyr23@aol.com
The Research Paper session will be Sunday from
12:15-4:15pm (view research paper abstracts)
The Poster Session and Reception will be Monday from 4:00-6:00pm in
conjunction with the Seed Issues Forum (view
poster abstracts)
Research Papers
Session 1 12:15 – 2:15pm
Adriel Garay, Oregon State University
(two presentations)
- Methodology to Develop a Uniform Blowing
Procedure In Grass Seeds (Tall Fescue)
- Better Alternative to Breaking Multiple
Seed Units in Tall Fescue
Sabry Elias, Oregon State University
- Effect of Germination and Fluorescence on
Plant Type Produced in Ryegrass
Reed Barker, Grass Genomic Testing
- Allelic Discrimination as an Aid in
Determining Genetic Purity in Ryegrass
BREAK 2:00-2:15pm
Session 2 2:25 – 4:15pm
Miller McDonald, Ohio State
University (two presentations)
- American Seed Technology Using Distance
Education
- A New Educational Resource: Seed Testing
DVD
Jim Woltz, Syngenta Crop Protection
- Analysis of Seed Treatment Loading Rates
Cindy Finneseth
- Developing a Standard Seed Testing
Protocol for Eastern Gramagrass (Tripsacum dactyloides)
Sabry Elias
- Suggested Tolerances for Tetrazolium
Tests
Research Paper
Abstracts
Methodology to Develop A Uniform Blowing
Procedure in Grass Seeds: An Example with Tall Fescue
Adriel Garay*, Sabry Elias, and Heather Nott
Oregon State University Seed Laboratory
Uniform Blowing Procedure is a technology that
can be used to separate lightweight inert matter in grass seed samples.
The benefits of this method have been demonstrated for many years with
orchardgrass, Kentucky bluegrass and others. In 2006, the master
calibration sample concept and the use of air velocity calibration were
incorporated to the AOSA Rules. Based on these new innovations, a
systematic research was conducted to develop a uniform blowing procedure
for tall fescue. The studies started by finding an optimum blowing point
to separate light inert from heavy pure seeds and concluds with a rule
proposal to AOSA-SCST as follows:
First, a preliminary blowing point was
identified by blowing samples at increasing air velocity points and
assessing the blowings visually for presence of caryopsis, using the one
third-caryopsis size rule. The planting value of the fractions blown out
was evaluated by germination tests. The results led to a preliminary
identification of the “location of the optimum blowing point”.
Second, the blowing point was validated
across a larger number of samples representing different varieties, years,
production locations, and seed sizes, using the 1/3 caryopsis size rule.
The 100-seed weight of the material blown out and retained portions were
measured. Additionally, the germination of the structures blown out and
the retained heavy fraction was tested. All these studies made it
possible to understand the planting value of the light portion and the
retained heavy portion and demonstrated that the blowing point chosen
was adequate across the broad range of samples tested.
Third, master calibration samples of
proven uniformity were developed. This step is critical because seed
laboratories cannot use a blowing procedure unless calibration samples of
proven uniformity are available. This step made it possible to have
calibrations samples for the referee studies so that all labs can find
comparable blowing points in their specific blowers.
Fourth, uniformity across blowers was
tested. The first study was conducted in-house using seven blowers and
many blind samples. This study was followed by a national referee where
labs calibrated their blowers with the “tall fescue master calibration
samples” provided to them and used 3 blind samples with different levels
of light inert content. A second national referee was conducted in late
2007 to encourage more participation and familiarization with the new
method. Regardless of the amount of lightweight inert present in the blind
samples, all labs were able to blow out comparable amounts of light inert.
This proved that, the new standard blowing procedure contributes to
uniform separation of light inert. As a result, a rule was proposed to the
AOSA-SCST to add tall fescue to the list of species that use blowing
procedure.
The stepwise methodology used will be
illustrated during the research presentation. The advantages of the new
method for testing Tall fescue will be discussed. The importance of the
methodology used to develop blowing procedures for other species will be
discussed.
Better
Alternative to Breaking Multiple Seed Units in Tall Fescue
Adriel Garay, Heather Nott and Sabry
Elias
Oregon State University Seed Laboratory
The AOSA Rules for
Testing Seeds treats multiple florets in grasses differently. For example
in tall fescue and ryegrasses, it requires the analysts to break them
apart manually to estimate the inert and pure seed units, which is time
consuming and can create variability. In orchardgrass and fine fescues,
it uses the factor method, which is more time efficient and reduces
subjectivity. Kentucky bluegrass, which uses a blowing procedure, multiple
seed units (MSU’s) are left intact. The last option is efficient,
eliminates subjectivity, does not change the nature of the sample and the
result reflects the true condition of the seed as it is being marketed and
planted.
Research was conducted to determine if a
better alternative to breaking multiples can be identified for tall
fescue. The research included the following steps:
First, the frequency of multiple
florets in tall fescue samples was measured using samples from 2006 and
2007 crop years. The results in both years indicated that 96% of samples
contained less than 50 multiples and less than 1% of samples showed 100
multiples or above. The low number of multiples present in the sample
suggested that even if all multiples are left intact, its potential to
influence purity and germination results would be small.
Second, blowing was used to determine
if light weight multiples, which contain no caryopsis, can be separated.
Regardless of the number of multiples present in the sample, blowing
lifted most empty multiples which did not show germination value. On the
other hand, most of the multiples that remained in the pure seed portion
contained caryopsis larger than 1/3 and the majority of them germinated.
This indicated that if a blowing procedure is used, tall fescue florets in
the light fraction (including multiples) can be considered inert; whereas
those in the heavy portion (including multiples) can be considered pure
seed.
Third, the new method (blowing tall
fescue first and leaving the multiples intact) was compared with the
current AOSA method (where blowing is not required and multiples have to
be broken apart). This comparison was performed in-house and followed by a
national referee study. The new method produced comparable results to the
current AOSA method, furthermore, when the number of multiple florets
neared 100 in the blind samples, the new method produced more uniform
results. A second year referee demonstrated that breaking or not breaking
multiples present in the heavy portion, produced comparable germination
results. This indicates that multiples found in the heavy portion (after
blowing) has planting like single pure seed units.
The time efficiency was measured during the
national referee study. All participant labs saved time using the new
method over the current AOSA method. Based on all the above studies, a
rule change is proposed. The sample would be blown using the proposed
blowing procedure for tall fescue, then, any multiple present in the light
portion would be considered inert and multiples present in the heavy
portion would be considered pure seed units. In essence, tall fescue would
be treated the same as Kentucky bluegrass. The beneficial implications of
the new method for testing tall fescue will be discussed.
Effect of Germination and Fluorescence on Plant Type
Produced in Ryegrass
Sabry Elias and Adriel Garay
Oregon State University Seed Laboratory
Some ryegrass samples may
achieve maximum germination and express maximum fluorescence or most of
the fluorescent trait before the 14-day test period. However, the
Cultivar Purity Testing Handbook states “Do not remove non-fluorescent
seedlings before 14 days”, regardless of whether the sample attains
maximum germination potential before the 14d test period. This study was
conducted to explore the possibility and conditions under which the
germination and fluorescence tests can be ended before 14 days. There is
no published data to quantify or explain the relationship between speed of
germination and rate of fluorescence over time. Research has been
conducted at the Oregon State University Seed Laboratory to study the
relationship between germination, fluorescence and grow out tests, and the
effect of pre-chilling treatment on the speed of germination and
fluorescence. The first study showed that the germination percentage of
117 out of 142 pre-chilled perennial ryegrass samples did not change from
the first count (7d) to the final count (14d) or increased by 1%.
Similarly, the fluorescence percentage of 132 out of the 142 samples did
not increase in the final count compared to the first count (7d). All
tests were conducted within 1-2 months after harvest in 2006. A
national referee study was conducted in 2007 to determine the rate of
germination and fluorescence of perennial, annual and intermediate
ryegrass samples at 7, 10, 12 and 14 days. Nineteen laboratories from CA,
FL, IA, IL, IN, KY, MI, MO, OR, PA, SD, TX, WA, WI, and Canada
participated in this referee. Ten seed lots were used in the study
representing various varieties from 2006 and 2007 crops. Perennial,
annual, and intermediate ryegrass samples that reached maximum germination
also expressed near full fluorescence at 7 or 10 days with some
exceptions. A study at the OSU seed lab is being conducted to determine
whether ending the germination/fluorescence test before 14 days would
result in missing some annual ryegrass contaminants. The preliminary
results indicated if a sample reached maximum germination and if the
variety fluorescence level (VFL) description of a ryegrass cultivar is low
(e.g., below 2%) and the number of the fluorescent seedlings in the first
count (7d) is low (i.e., below the VFL), it is unlikely that this sample
will have more fluorescent seedlings in the final count to affect the
final results. If the VFL and the number of fluorescent seedlings in the
first count (7d) is high, a full 14-day test period would be needed as a
safeguard to avoid the potential of missing annual plant contaminants.
Allelic Discrimination as an Aid in Determining Genetic
Purity in Ryegrass
Reed E. Barker*
Sharon Davidson
Grass Genomic Testing, Inc. Agri Seed
Testing, Inc.
1962 Davcor St., SE 1930
Davcor St., SE
Salem, OR 97302 Salem,
OR 97302
The seedling root fluorescence (SRF) test has
been used to distinguish perennial (Lolium perenne L.) and annual
(or Italian) (L. multiflorum) ryegrass since the 1930s. At times
the test has been unreliable and overestimates the amount of annual
contamination. The objective of our research for the past several years
has been to find and characterize specific genes that may be associated
with growth type. We have identified alleles (alternate forms of a gene)
of three genes associated with flowering control in grasses. Alleles from
two of the genes were effective in predicting growth type. Leaf tissue was
harvested from seedlings used in an SRF test and DNA extracted using
commercially available purification kits. To cut down on lab costs, only
seedlings with SRF, plus five to ten seedlings with non-SRF were analyzed
on a real-time PCR machine in Allelic Discrimination (AD) mode. Twenty
cultivars were tested in a proof-of-concept panel. Following the SRF test,
all seedlings were transplanted to a high intensity growth chamber under
continuous light for a grow-out test (GOT) that lasted for 84da. Plants
reached heading throughout the full time of the GOT, but approached a
plateau at about 70da. These results supported that the GOT should be
longer than the suggested 42da in order to be effective. Further, SRF was
high in the earliest heading plants and declined in later heading plants,
but never fell below 30% of the plants heading in each 7da increment
demonstrating the problems that the SRF test has in predicting
contamination. In contrast, however, AD using alleles from the two genes
detected growth type differences to about a 3% level, a level equivalent
to a 70da or greater GOT. Detection error rates for the non-SRF plants was
less than 0.5% based on presence of two out of three markers that included
SRF and alleles of the two genes we used in the study. Allelic
Discrimination at the single nucleotide level based on alleles of the
Vrn-1 and ID1 genes are an effective and rapid method to
predict growth type contamination in ryegrass.
American
Seed Technology Using Distance Education
M. B. McDonald
Seed Biology Program
Department of Horticulture and Crop Science
The Ohio State University
Columbus, OH 43210-1086
mcdonald.2@osu.ed
Today’s
American seed industry is global in stature. Seeds are increasingly
produced in other countries based on advantages in personnel costs,
counter-season production locations in the southern hemisphere, geographic
location, and ability to produce a diversity of seed crops ranging from
recalcitrant to orthodox seeds. Because of these necessary and
increasingly complex international approaches to successful global
competition, the seed industry requires students with a broader and deeper
knowledge of various methods for high quality seed production. The
objective of this research is to provide a new approach to global seed
technology education that forges a consortium of five leading
international agricultural research institutions with strengths in seed
biology: The Ohio State University, USA; University of California Davis,
USA; Lincoln University, USA; Escola Superior Agricultura “Luiz de Queiroz,”
Brazil; and Pontificia Universidad Catolica de Chile. This consortium
provides higher quality education in seed biology by drawing on the
expertise of more faculty with a diverse knowledge of approaches to
successful seed production in differing countries. Results of the
consortium allow the use of advances in distance education technology that
permit the teaching of courses and offering workshops using internet
videoconferencing technology at any location in the world. Two courses
(International Seed Production, International Seed Physiology) have been
offered using this technology. The courses are listed on the web at
HUhttp://seedbiology.osu.eduUH,
click courses and HCS 630 and 631. Students can use the text, PowerPoint
presentations, and podcasts as preview and review of online interactive
videoconferencing classes. Each institution lists the courses as their
own courses with visiting faculty providing lectures. In this way, they
are able to obtain local student credit hours. Other results of the
consortium include the collaborative development of DVDs for coffee,
tropical forage grass, maize, and sunflower seed production. Each
institution is viewed as a node in the consortium with an ultimate
objective to provide a node in each country in the world thus expanding
expertise in seed biology. The provision of students with greater
international perspectives of the global seed industry and the continuing
development of educational seed production resources will build a more
globally competitive American seed industry.
A New Educational Resource: Seed Testing DVD
Miller B. McDonald
Department of Horticulture and Crop Science
The Ohio State University
Columbus, OH 43210-1086
mcdonald.2@osu.edu
Seed testing is a complex task requiring many
diverse skills. Because of this complexity, one of the important aspects
of professional meetings is to convene workshops to enhance analyst
standardization. Other approaches to improve standardization are
continuing education and publication of detailed handbooks such as the
Seed Technologist Training manual. But, these approaches require the seed
analyst to travel to the site of learning which requires time and cost.
The development of DVDs highlighting various aspects of seed testing is a
superior approach to education of seed analysts. Such a DVD has been
developed and contains the following modules: The importance of seed
testing, seed identification, seed sampling, physical purity testing,
germination testing, seed testing tolerances, vigor testing, seed health
testing, seed moisture testing, and genetic purity testing. Because the
Rules are dynamic and changing yearly, this DVD will necessarily require
periodic updating, but the digital format easily permits these changes
simply by cutting and pasting. The principal advantage of this DVD is
that it allows the professional seed technologist to prepare for
certification examinations and permits those in the industry to remain
current in latest technological developments. This approach also has
benefits for non-traditional students and students at community colleges
and agricultural technical schools that prepare students for four-year
programs. Finally, such an approach allows the student the opportunity to
learn at their own pace on a computer – an ideal and preferred approach
counter to contemporary classroom settings. Portions of this DVD will be
demonstrated.
Analysis of Seed Treatment Loading Rates
James Woltz, Syngenta Crop Protection, Stanton, MN and
Barbara Stefl, Cognis Corporation, Cincinnati, OH
Advances in seed treatment application and
formulation technology have resulted in more precise dosing based upon
“per seed” loading rates. This has led to treatment loading analysis
becoming an integrated component of quality assurance programs. Analysis
of seed treatment loading rates has traditionally been done using
chromatography following extraction of the treatment from the seed. Now,
a Fourier Transform Near Infrared (FT-NIR) method has been developed for
non-destructive analysis of the ai on the seed. In 2006 and 2007, studies
have been conducted to measure sample loading variability and assess the
suitability of new analytical technologies for determining chemical
loading analysis. There are several sources of variability: among
samples, treating machinery and analytical method. Within a seed lot,
seed weight from sample to sample could vary between from 0.7 to 2.5% for
corn (Zea mays L.), 1.2 to 3.5% for soybean (Glycine max
Merrill), and 0.8 to 2.9% for cotton (Gossypium spp.), depending
upon sample size. Across 10 samples from a single batch of treated seed,
loading results could vary as much as 9%. Comparisons of results from
different testing methodologies for the same sample showed standard
deviations of ~2% for High Performance Liquid Chromatography to ~6% for
FT-NIR. A ring test demonstrated that FT-NIR was an acceptable
alternative to other methods of analysis for rapid detection of gross
chemical misapplication.
Developing a standard Seed Testing Protocol for eastern gamagrass [Tripsacum
dactyloides (L.) L.]
Cindy H. Finneseth1* and Robert L.
Geneve2.
1Division of
Regulatory Services, 103 Regulatory Services Bldg., University of
Kentucky, Lexington, KY, 40546 USA. Email:
Cindy.Finneseth@uky.edu
2Dept. of Horticulture, N-318 Ag. Science N., University of
Kentucky, Lexington, KY 40546 USA. Email:
rgeneve@uky.edu
Eastern gamagrass (Tripsacum dactyloides
L.), a native warm-season perennial, is being promoted as a grass for
forage, wildlife, and conservation purposes. Widespread use, however, is
limited by germination and stand. Poor stands have been attributed to a
combination of seed dormancy and low seed quality. Additionally, current
AOSA Rules for Testing Seeds are limited in assessing seed quality. The
objectives of this study were to review the current purity guidelines and
develop preliminary recommendations for a standardized germination testing
protocol for eastern gamagrass. Seed counts were conducted on 40 seed
lots, including 8 cultivars and 10 ecotypes or selections. The average
number of seed per gram ranged from 7 to 18 (3195 to 8344 seed per pound,
respectively). The current AOSA Rules require analysis of 205 g., which
is adequate for many cultivars. However, for large-seeded cultivars and
collections the working weight for purity analysis should be increased to
340 g. The seed lot used to investigate germination temperature regimes
demonstrated typical performance for eastern gamagrass seed lots, with a
germination potential of approximately 67% based on initial TZ viability
assessment. Stratification and germination temperature had a significant
impact on germination percentage. Stratification between 2 and 8 weeks at
5ºC or 10ºC enhanced germination speed, total germination and reduced
dormancy compared to untreated seeds. Alternating temperatures were
generally more effective in promoting germination and minimizing dormant
seed than constant temperatures. Optimal germination occurred at 15/25,
15/35 or 20/30ºC (16 hr/8 hr), where germination averaged approximately
64% for seeds stratified at 10ºC for 6 weeks. In contrast, seeds
germinated at constant 15 or 20ºC germinated at less than 5 and 12%
without and with stratification, respectively. Germination temperature
contributes to inconsistent seed germination; therefore, it is important
that a standardized protocol is developed for this species. Based on
preliminary testing, 15/25, 15/35 or 20/30ºC are acceptable temperature
regimes for standard germination testing, however, before a Rules change
is proposed, testing must be completed using additional seed lots and
across laboratories to ensure low variability and repeatability.
Suggested Tolerances for Tetrazolium Tests
Sabry Elias, Stephanie Maguire, and
Annette Miller
Regulators use tolerances to test the
truthfulness of labeling and for comparing test results within and among
laboratories. Tolerances are also used for service tests and for quality
control purposes. The tetrazolium (TZ) test is increasingly used as a
viability test for many crops because of its advantages, yet the AOSA does
not have tolerances for that test. This year (2008), TZ tolerances are
proposed to be added to the AOSA Rules by the authors of this paper.
Tolerances are the largest non-significant differences between two values.
Data of tetrazolium tests are expected to follow the binomial
distribution, assuming sampling variation in the absence of experimental
error, as do data of germination tests. However, in practice there are
sources of experimental errors in each test. Experimental errors have to
be identified, quantified and taken into consideration when calculating
tolerance values. Possible sources of experimental error in the TZ testing
may include but not limited to: improper cutting or piercing technique,
variation in seed evaluation due to analyst experience, using different
concentrations of TZ solutions, and using different methods and
temperatures in moistening or preconditioning the seeds. The principles of
calculating the TZ tolerances are established by Miles in his Handbook of
Tolerances in 1963 and were revised by Michael Kruse who quantified the
experimental error factor (f) by calculating the ratio between the
observed standard deviation (s) among replications and the expected
standard deviation (s)
based on the binomial distribution. Kruse developed tables for comparing
two TZ test results of 400 seed each. The authors of this paper computed
the tolerances for two tests of 200 seeds each, and for two tests, one 200
seeds and the other 400 seeds. This paper will explain the basis for
calculating the experimental error for TZ tests as well as for computing
the tolerance values.
An
index to quantify the relationship of seed moisture loss rate to seed
desiccation tolerance in common vetch
Nezar H. Samarah1’2, R. E. Mullen1, A. Alqudah2
1 Department of Agronomy, Iowa State University, Ames, IA 50011,
USA.
2 Department of Crop Production, Jordan University of Science
and Technology, Irbid, Jordan.
Common vetch
(Vicia sativa L.) seeds are desiccation intolerant when seeds are
harvested at immature stages of developme and extracted from pods before
drying. Drying immature seeds in intact pods may improve desiccation
tolerance in association with slow drying rate. Therefore the objective of
this experiment was to develop an index to quantify the rate of seed
moisture loss of common vetch seeds subjected to four drying methods to
their desiccation tolerance. During the reproductive growth stage, seeds
were harvested at four development stages: 1) beginning seed fill (BS), 2)
full-size seeds (FS), 3) yellow pods (Y), and 5) brown pods (B). Seeds
were dried at 20oC ± 2 by four methods: 1) dried in intact pods, 2)
extracted from pods and dried under ambient conditions (Ambient), 3)
extracted from pods and rapidly dried over low relative humidity for 6
days (Low RH), 4) extracted from pods and slowly dried over a gradually
declining relative humidity for 6 days (Gradually Declining RH). Seed
moisture content was measured during the drying period. Seed desiccation
tolerance was estimated by measuring the percentage of normal seedlings in
standard germination test for air-dried seeds. An index was developed to
quantify the drying rate over time. Drying seeds in intact pods improved
desiccation tolerance (the percentage normal seedlings in standard
germination) as compared with those seeds dried either under ambient, low
relative humidity, or gradually declining relative humidity when seeds
were harvested at the BS, FS, and Y stages. Slowly drying seeds under a
gradually declining relative humidity improved the desiccation tolerance
of the seeds harvested at FS stage as compared with those dried under
ambient or low relative humidity. Drying seeds in intact pods or over
gradually declining relative humidity slowed the drying rate as estimated
by seed moisture loss index. As seed moisture loss (SML) index increased,
seed desiccation tolerance decreased. A dramatically reduction in seed
desiccation tolerance was observed at SML index of 19. These data
emphasized that desiccation tolerance is an independent mechanism of seed
development which can be acquired in seeds harvested as early as beginning
of seed fill.
Stratification, hydrogen peroxide and germination temperature regime
influence germination and dormancy release in eastern gamagrass [Tripsacum
dactyloides (L.) L.]
Cindy H.
Finneseth1*, Robert L. Geneve2 and Joshua D. Klein3.
1Division of Regulatory Services, 103 Regulatory Services Bldg.,
University of Kentucky, Lexington, KY, 40546 USA. Email:
Cindy.Finneseth@uky.edu.
2Dept. of Horticulture, N-318 Ag. Science N., University of
Kentucky, Lexington, KY 40546 USA. Email:
rgeneve@uky.edu
3Institute of Plant Sciences, ARO-Volcani Center, Bet-Dagan, Israel.
Email: vcjosh@agri.gov.il.
Eastern gamagrass (Tripsacum dactyloides L.)
is a warm-season perennial grass recommended for forage, wildlife, and
conservation purposes. However, its widespread adoption has been limited
by poor germination and stand establishment. Less than adequate stands
have been attributed to a combination of seed dormancy and low seed
quality. The seed lot used for this study demonstrates the typical seed
performance for eastern gamagrass with a germination potential of
approximately 67% based on pre-treatment TZ viability assessment and lab
germination in untreated seeds at approximately 15%. The objective of this
study was to investigate whether germination temperature contributes to
inconsistent seed germination following dormancy release by stratification
or H2O2. Stratification between 2 and 8 weeks at
5ºC or 10ºC as well as H2O2 application enhanced
germination speed, total germination and reduced dormancy compared to
untreated seeds. Stratification was more effective than H2O2
for dormancy release, but the impact on germination speed was similar.
Germination temperature had a significant impact on germination percentage
in both stratified and H2O2 treated seeds.
Alternating temperatures were generally more effective in promoting
germination and minimizing dormant seed than constant temperatures.
Optimal germination occurred at 15/25, 15/35 or 20/30ºC (16 hr/8 hr),
where germination averaged approximately 64% for seeds stratified at 10ºC
for 6 weeks and 32% for seeds imbibed in 20% H2O2
for 18 hours. In contrast, seeds germinated at constant 15 or 20ºC
germinated at less than 12 and 15% for stratified and H2O2
treated seeds, respectively. These data suggest that germination
temperature contributes to poor stands observed for stratified seeds sown
under field conditions. Additional work will determine if there is a
benefit for combining stratification and H2O2
treatments to decrease seed sensitivity to germination temperature and
possibly improve stand establishment.
Red to Far-Red Ratio during Seed Development Affects
Lettuce Seed Germinability and Storability
Samuel Contreras1, Mark A. Bennett2*,
David Tay3, James Metzger2, Haim Nerson4
1Departamento
de Ciencias Vegetales, Pontificia Universidad Católica de Chile, Casilla
306-22, Santiago, Chile
2Department of Horticulture and Crop Science, Ohio State
University, Columbus, OH 43210-1086, USA
3Ornamental Plant Germplasm Center, Ohio State University, Columbus,
OH 43210-1086, USA (current address: International Potato Center, Apartado
1558, Lima 12, Peru
4Agricultural
Research Organization, Department of Vegetable Crops, Newe Ya’ar Research
Center, P.O. Box 1021 Ramat Yishay, 30095, Israel
Lettuce
(Lactuca sativa) is one of the most important vegetable crops in
the world. Thermoinhibition and photodormancy are two characteristics of
lettuce seed that frequently reduce germination and seedling emergence in
the field. In addition to germinability, storability is an important
aspect of lettuce seed quality. The main objective of this study was to
evaluate the effects of producing lettuce seeds under light with
contrasting red to far-red ratios (R:FR) on seed germinability and
storability. ‘Tango’ lettuce seeds were produced in growth chambers under
one of two treatments: i) Red-rich light (R-treatment), and ii)
Far-red-rich light (FR-treatment). Seeds produced under the FR-treatment
were 5% heavier than seeds from the R-treatment, but in both cases the
percentage normal seedlings germinated at 20°C-light was approximately
100%. When germinated in the dark, seeds from the R-treatment germinated
100% between 12 and 23°C, and over 50% at 30°C, while seeds from the
FR-treatment germinated less than 35% between 12 and 23°C and less than 5%
at 30°C. When germinating under light, seeds from the R-treatment had
higher germination percentages and rates under a broader range of
temperatures, having less thermoinhibition than seeds from the
FR-treatment. Seeds from the R-treatment had lower abscisic acid (ABA)
content and were better able to germinate when exposed to external ABA
concentrations and reduced water potentials than seeds from the
FR-treatment. Seed storability as assessed by the accelerated aging test
was higher in seeds from the FR-treatment. These results suggest that seed
production under environments with higher R:FR light represents a novel
approach to the production of lettuce seeds with lower thermoinhibition
and photodormancy; however, reduction in seed size and storability are two
undesired consequences.
Temperature During Seed Development Affects Size,
Germinability and Storability of Lettuce Seeds
Samuel
Contreras1, David Tay2 and Mark A. Bennett1*
1Dept. of Horticulture and Crop Science, Ohio State University, 2021
Coffey Rd, Columbus OH 43210-1086, USA
2Ornamental Plant Germplasm Center, Ohio State University, 670
Vernon Tharp St, Columbus OH 43210-1086, USA
Seed germinability and storability are
important aspects of seed quality determined by the genotype and
environment of seed development. Lettuce (Lactuca sativa) is one of the
most important vegetables in the world. The objective of this study was to
determine how temperature of the mother plant environment affects lettuce
seed quality. Seeds of cv. Tango were produced in growth chambers under
one of two treatments: i) high temperature (HT), with day/night
temperatures of 30/20°C, respectively, and ii) low temperature (LT), with
temperatures of 20/10°C. Seeds produced at LT were 25% heavier than seed
from HT, however germination at optimal conditions (20°C-light) was
similar for both treatments. Seeds from HT presented better dark
germination at 18, 24 and 29°C. Germinability (% and rates) under light at
temperatures between 20 and 33°C was similar for seeds from both
treatments, however at temperatures between 33 and 40°C seeds from HT
performed better than those from LT. When germinated at negative osmotic
potentials, germinability of seed from HT was less affected than LT. After
accelerated aging (41°C, ~100%RH, 72 h) germination of normal seedlings
was higher for seeds from HT. Germination after 1, 2 and 3 months of
storage at 30°C and 74% RH was better for seeds from HT. The critical
moment for temperature effects was also studied. Seed weight, dark
germination at 30°C and germination at low osmotic potential were shown to
be determined earlier during seed development (before 5 and 4 days after
flowering for seeds from LT and HT, respectively). On the other hand, seed
storability was determined at the end of seed development, after
physiological maturity (~15 and 10 days after flowering for LT and HT
seeds, respectively). In conclusion, for the lettuce cv Tango, higher seed
germinability and storability were attained when seeds were produced at
higher temperatures.
Comparison of Two Paper Towel Media Methods on Triticum
aestivum Germination Results.
S.K.
Dammen, K.A. Fiedler, A.L. Patin
SGS Mid-West Seed Services, Inc.
Brookings, South Dakota USA
The objective of this study was to evaluate
two paper towel methods; horizontal unrolled towels versus vertical
positioned rolled towels, as germination test methods for Triticum
aestivum (wheat). Twenty commercial seed lots of Triticum aestivum
were evaluated. The methods, substrata type, temperature and
duration of the germination tests were identical. Four sheets of
38#, 12” x 24” paper toweling were utilized for the vertically positioned
rolled towel method and two, 76#, 16” x 24” paper towels were used for the
horizontal unrolled towel method. Germinations were conducted at
20°C and evaluations were performed at 7 days. The rolled paper
towel (T) method had 100 seeds placed on a pre-moistened flat towel.
After planting, the towel was folded over, rolled up and placed
vertically in a container. This planting process was repeated four
times for each sample. The horizontal paper towel method utilized
two 76# towels flat on a tray. Water was applied to the tray and
paper towel as tray was conveyed under a spraying device. Four 100
seed replicates were planted on the tray while the towel remained
horizontal and unrolled. After planting, the trays were inserted
into a food service type germination cart and incubated at 20ºC. No
significant differences in standard germination percentages were observed
between the two methods. However, the horizontal paper towel method
eliminated three planting and evaluation steps (watering, rolling up and
unrolling to evaluate) thus producing a more streamlined and lower labor
cost method.
Creped Cellulose Paper covered with Sand as a Germination Medium
Laura Carlson, Larry Prentice
SGS Mid-West Seed Services, Inc.
Brookings, South Dakota USA |