Volume 26, No. 1, 2004

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(pp. 5-16)
Identification of Avena and Oryza Noxious Weed Seeds Using High-Performance Liquid Chromatography
G.W. Freeman*, J. C.Wang, and P. P. Lehtonen
Surveillance, sampling, and testing for federally listed noxious weeds costs the United States Department of Agriculture substantial amounts of money every year. Because some species of noxious weeds look like related crop species, visual identifications of the seeds are not always accurate. Reversed-Phase High-Performance Liquid Chromatography  (RP-HPLC) of cereal grain proteins has received much attention in recent years as a quick and efficient means of seed identification.

A study of Avena abyssinica Hochst., Avena barbata Pott ex Link, Avena fatua L., Avena longiglumis Durieu, Avena sterilis L., Avena strigosa Schreb., Avena hybrids, Oryza sativa L., Oryza longistaminata A. Chev. and Roehr,  Oryza punctata Kotschy ex Steud., and Oryza rufipogon Griff. was undertaken to determine if RP-HPLC could be adapted to the identification of these species. Prolamin and glutelin protein fractions of single seed extracts were separated using liquid chromatography and the chromatograms of the species were compared. It was demonstrated that all the species studied had distinct peak patterns, which enable them to be identified. Protein analysis of Avena hybrids appears to provide information of the parentage of those seeds. Dichotomous keys were developed to enhance the interpretation of the peak differences in the species chromatograms. RP-HPLC was shown to be a quick, repeatable and reliable method of Avena and Oryza species identification.
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(pp. 17-26)
Comparison of Purity Testing Methods of Weeping Alkaligrass (Puccinellia distans (Jacq.) Parl.)
D. J. Lionakis Meyer* and J. Effenberger
Weeping alkaligrass (Puccinellia distans (Jacq.) Parl.) is a small-seeded grass species similar in size to Kentucky bluegrass (Poa pratensis L.) and rough bluegrass (Poa trivialis L.). Two purity methods were compared: 1) the hand separation method (HSM), requiring microscopic examination of each seed unit to insure the presence of at least one caryopsis in each seed unit, and 2) the Uniform Blowing Procedure (UBP) similar to the procedure described in the Association of Official Seed Analysts’ Rules for Testing Seeds used for several species of Poa, in which empty and under developed florets are removed mechanically via air stream separation in a General type seed blower.

The study was conducted in two phases: Experiment I determined a UBP for weeping alkaligrass that would provide pure seed and pure live seed percentages similar to those obtained with the currently accepted HSM; and Experiment II consisted of a collaborative study among laboratories to validate the UBP as a viable alternative to the HSM for purity testing of weeping alkaligrass. These two experiments demonstrate that use of a mathematical factor of 0.76 in combination with the Kentucky bluegrass blowing point achieves pure seed percentages that are not statistically different from those obtained by the HSM. In addition, the UBP was demonstrated to be a 42% more time efficient method of purity testing among participating laboratories.
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(pp. 27-37)
Effect of Maturity Stage on Seed Germination and Vigor of Common Vetch (Vicia sativa L.)
N. H. Samarah* and R. E.Mullen
Common vetch (Vicia sativa L.) is an important legume crop for feed in the Mediterranean  regions where high vigor seed is needed to overcome limited moisture stress at planting time. Early harvesting of common vetch grown for seed may decrease seed losses due to shattering, but may result in reduced seed germination and vigor. Field experiments were conducted to study the effect of maturity stage on seed germination and vigor of common vetch.

Pods were harvested at five developmental stages: beginning seed fill (BS), full seed pod (FS), greenish-yellow pod (GY), yellow pod (Y), and brown pod (B). Seeds harvested at different stages were germinated under osmotic stress levels of 0, –0.4, –0.8, –1.2, and –1.6 MPa, and after three accelerated aging (AA) treatments of 39°C for 72 h, 39°C for 96 h, and 45°C for 48 h). Seed germination percentage, germination rate index (GRI), shoot and root lengths, and electrical conductivity of seed leachate (EC) were measured for each of the germination environments. Maximum seed germination, GRI, and shoot and root length under no osmotic stress (0 MPa) were attained when seeds were harvested at or after the GY stage. Delaying seed harvest to the B stage improved seed germination, GRI, shoot and root lengths under osmotic stresses of –0.4 and –0.8 MPa.Maximum germination after AA and the lowest EC values were achieved when seeds were harvested at or after the yellow pod stage. Incubating seeds at 39°C for 94 h and at 45°C for 48 h under 100% RH were the best AA treatments to discriminate and evaluate seed vigor of common vetch. In conclusion, delaying harvest of common vetch seed until the yellow or brown pod stages may improve seed germination and vigor under a wide range of field conditions.
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(pp. 38-50)
Genetic Variation in Germination Attributes and Response to Seed Accelerated Aging in Western Hemlock
Y. A. El-Kassaby,* A. Benowicz and D.G.W. Edwards
Orchard produced seeds of western hemlock (Tsuga heterophylla (Raf.) Sarg.) clones were subject to standard germination (20 clones) and accelerated aging (12 clones) tests. Based on the first test, strong genetic control over the germination attributes (germination capacity, germination value, peak value and germination speed) was found as indicated by the high values for broad-sense heritabilities ranging from 0.88 to 0.92 and from 0.72 to 0.85 for stratified and unstratified seeds, respectively.

Seed stratification increased the speed of germination, but had no effect on germination capacity. In the accelerated aging test, seeds were exposed to 37.5°C and 100% relative humidity for 0 to 15 days at 3-day intervals and then germinated with or without stratification. Accelerated aging had significant effect on all germination attributes and accounted for between 32.3 to 88.3% of the total variation. The ability to germinate decreased at different rates across the clones as aging progressed. Stratification improved germination capacity of seeds aged for three days compared to unstratified seeds aged for the same period, but showed no benefits with respect to any germination attribute after three days of aging. Germination of stratified seeds was progressively more delayed as the duration of aging increased while germination speed of unstratified seed increased after three and six days of aging and decreased thereafter. Results have implications for the management of western hemlock genetic resources at the level of commercial seedling production and with respect  to the use of seed banks for ex situ gene conservation of this species.
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(pp. 51-64)
Effect of Differential Rates of Drying on Viability and Storability in Recalcitrant Sal (Shorea robusta C.F. Gaertn) Seeds
Boby Varghese, Georg von Wuehlisch and S.C. Naithani*
The effect of differential rates of drying on viability was examined in mature seeds of sal (Shorea robusta C.F. Gaertn) during storage at ambient conditions. The initial seed moisture content (fwb) was 42.1% and the percentage of seed germination was determined after drying slowly (air-dried naturally) and rapidly (over silica gel) compared to seeds held in vermiculite.

Seeds became non-viable when desiccated to 19.5% and 9.8% moisture content in natural (slow) and silica gel (rapid) drying, respectively. The seeds dried rapidly over silica gel retained higher germination (33%) at lower moisture content (13.3%) compared to the natural drying. Wet storage in vermiculite was not successful and eventually led to loss of seed viability despite higher moisture contents. Storage experiments carried out with undried (42.1%) and rapidly dried (37.5, 34.9, 31.8, 25.4 and 21.0% moisture content) seeds at temperatures of –196, –20, 0, 15 and 25°C, showed maximum viability for undried seeds at 15°C. The undried and dried seeds could not tolerate freezing, sub-freezing and cryo-temperatures and were killed within one day of storage. Results suggest that rapid drying of recalcitrant S. robusta seeds to lower moisture levels excludes the possibility of desiccation induced damage compared to the naturally dried seeds, though the long-term storage of these rapidly dried seeds at various temperatures was not possible.
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(pp. 67-74)
Saturated Salt Accelerated Aging (SSAA) and Other Vigor Tests for Vegetable Seeds
Mark A. Bennett,* Elaine M. Grassbaugh, Andrew F. Evans, and Matthew D. Kleinhenz
Obtaining uniform stands of vegetable crops in field or greenhouse environments is often challenging. Successful germination and seedling establishment is usually linked to several important factors, including

1) the use of high vigor seed; 2) planting at proper soil depths; 3) sowing into well prepared seedbeds with calibrated seeders and good seed singulation; 4) field selection and planting date decisions; 5) suitable cultivars; and 6) seed treatments. The emphasis of this presentation will be on seed vigor tests for vegetable seeds, yet all the factors listed above are closely tied to the concept of vigor. Definitions of vigor (Hampton and TeKrony, 1995) mainly describe the associated seedling establishment consequences of seed lots that differ in quality. The objectives of this manuscript are to 1) review the benefits of quality vegetable seeds; 2) discuss the connection of seed production and seed enhancement variables to seed vigor; and 3) summarize current and emerging vigor tests used for vegetable crop species.
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(pp. 75-85)
Applications of Hydrotime Analysis in Seed Testing
Kent J. Bradford* and David W. Still
Hydrotime is a way to describe the relationship between water potential (ψ) and seed germination rates and percentages. The minimum ψ that allows germination to be completed is called the base water potential (ψb). The germination rate (inverse of time to radicle emergence) increases linearly as the seed ψ increases above ψb to its maximum rate in water (ψ = 0 MPa).

As ψb values vary among individual seeds, germination rates also vary, resulting in lack of uniformity that can be quantified by the standard deviation in ψb values (σψb ). The hydrotime constant (θH) indicates the inherent speed of germination in a seed lot. Thus, hydrotime analysis quantifies the speed of germination (θH), the stress tolerance of germination (ψb) and the uniformity of germination for a seed lot (σψb ), which are all useful indicators of seed vigor. Hydrotime analysis of seed lots under diverse conditions allows them to be ranked according to their potential for successful emergence. It is also a valuable tool for developing and assessing seed enhancement treatments such as pelleting and priming. Hydrotime analysis can be simplified into an endpoint test that  could be useful for ranking seed lots according to vigor and for diagnosing seed lot  potential under stressful conditions.
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(pp. 86-91)
Update on Seed Priming: From Priming to Pregermination, and Back
Ir. G. Tonko Bruggink
Compared to untreated seeds, primed seeds (depending on the species and treatment)  have increased speed and uniformity of emergence, but one clear drawback is that their shelf life is reduced.

In recent years, methods were developed to improve longevity after priming, building on experience gained in research on induction of desiccation tolerance of pregerminated seeds. The benefits and limitations of priming and pregermination are discussed. Recently primed and pregerminated seeds have been used as model systems for studies on desiccation tolerance and shelf life and examples of such work are presented.
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(pp. 92-97)
The Paradigm SVA system
David C.McNertney
How would you like to be able to collect seed growth data, analyze that data, view it in simple graphical display and easily distribute it to your colleagues with just a few key strokes on your computer? With the Paradigm Research Corp.® Seed lot Vigor Assessment (SVA) System, version 4, a complete information system with functionality for data collection, analysis, display and distribution, that is what you can do. The SVA system provides automated objective data collection through the use of machine vision and image analysis.

The patented SVA system (US patent # 5,864,984) successfully measures seedling emergence and growth rate for a variety of crop species. In fact, the Paradigm SVA system can measure tiny seedlings such as tobacco and Lisianthus, many flower and vegetable crops such as Impatiens, pansies, lettuce, carrots, and tomatoes, and larger agronomic crops such as Canola, alfalfa, and sugar beets. With the new capability to handle both 4"x 4" and 6"x 9" sample dishes, the system can now accommodate even larger agronomic crop species such as corn and soybeans. Perhaps the most exciting new feature included with the Paradigm SVA, version 4 software is the PArZ ViewerTM (available via free download). It opens the new, easily distributed Paradigm Archive files automatically compressed or zipped by the program. Designed to function similarly to the Adobe® Acrobat® family of products, the Paradigm SVA system first collects and analyzes data, then ultimately packages this data in the form of .arz files (analogous to Adobe®.pdf files).Attaching these .arz files to an email message makes worldwide seed quality data distribution a simple, easy process. The PArZ ViewerTM then opens these .arz files to display and/or compare seed lot vigor data. In addition to providing easy test result data distribution, the functionality provided by the PArZ ViewerTM allows end users to independently specify their own minimum performance standards. In this fashion,the final results can be tailored to match various seed data consumers’ individual specifications.
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Ball Seed Vigor Index™

Robert Conrad
The Ball Vigor Index™ is a machine vision reading system to test the uniformity of seedling  cotyledons grown under commercial conditions in plug trays. The system has been in use for eight years to test the quality of bedding plants grown from seed. Some of the crops tested with this system are Impatiens, Petunia, Pansy, Marigold, Salvia, Begonia, Vinca and others.
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