Volume 34, No. 2, 2012

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Download Abstracts (free download) from oral and poster presentations given at the  102nd Association of Official Seed Analysts and the 89th Society of Commercial Seed  Technologists (AOSA/SCST) annual meeting held in Des Moines, Iowa on May 20–24, 2012

(pp. 163-172)
Lindera melissifolia Seed Bank Study in a Lower Mississippi Alluvial Valley Bottomland  Forest
K.F. Connor*, G.M. Schaefer, J.B. Donahoo, M.S. Devall, E.S. Gardiner, T.D. Leininger, A.D. Wilson, N.M. Schiff, P.B. Hamel and S.J. Zarnoch
Lindera melissifolia (Walter) Blume, or pondberry, is federally listed as an endangered shrub and grows in warm, humid lowland forests of seven states in the southeastern United States. The dioecious plants usually form clonal colonies as a result of rhizome sprouting. Although L. melissifolia can annually produce many bright red spicy scented drupes, information on reproduction of the species is limited to its clonal regenerative capabilities.

We examined the survival of L. melissifolia seeds held within bags for up to 1 y in a soil seed bank. Half of the bags were buried and the other half left on the soil surface. Additionally, bags contained seeds either with the oily fruit pulp removed or with drupes left intact. Results indicated that the presence or absence of the pulp does not  significantly affect seed survival. However,the viability of buried seeds was greater than 50% by the end of 1 y, whereas over 70% of the seeds left on the surface were rotten or missing. Buried seeds were seven times more likely to produce seedlings in the field than those left on the soil surface. Because L. melissifolia seedlings are not often observed in naturally occurring populations despite the production of viable seeds, it is likely that environmental conditions or other biotic factors limit the field distribution and  sustainability of seedlings.
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(pp. 173-182)
Ecotypic Differences in Switchgrass Seed Germination Responses to In Vitro Osmotic Stress
Ramdeo Seepaul, Bisoondat Macoon and K. Raja Reddy*
The use of switchgrass (Panicum virgatum L.) as a forage, conservation, and feedstock species is limited by its slow and erratic germination and inconsistent establishment, further exacerbated by variable soil moisture conditions. An in vitro study was conducted to determine osmotic stress effects on germination properties of four switchgrass cultivars, ‘Alamo’, ‘Cave-in-Rock’, ‘Kanlow’ and ‘Shelter’. Seeds were tested for germination in polyethylene glycol (PEG 8000) solutions at water potentials ranging from 0 to −2.0 MPa with 0.2-MPa increments, at 25 °C.

Six replicates of 100 stratified seeds were germinated and monitored at 6-h intervals from incubation. Maximum seed germination (MSG) and germination rate were estimated by fitting a 3-parameter sigmoidal function to germination time, which provided germination percentage, response shape and germination speed. Decreased osmotic potentials decreased MSG, while the time required for onset of germination increased across all cultivars. A cultivar by osmotic potential interaction for MSG (p < 0.0001) was observed. Cave-in-Rock had the greatest MSG followed by Shelter, up to −0.2 MPa. Responses were further analyzed by ecotype due to similar responses of Alamo and Kanlow (low land ecotypes) and Cave-in-Rock and Shelter (upland ecotypes). Theco types differed in median germination (p < 0.0001) and germination rate (p < 0.0001). Lowland ecotypes required 27% more time (24 h) to achieve 50% of MSG than upland ecotypes. Germination rate decreased with decreasing osmotic potential for both ecotypes. The developed ecotype-specific algorithms can be used in modeling germination under variable moisture conditions among switchgrass cultivars.
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(pp. 183-192)
Discriminating Pepper Landraces in Nigerian Gene Bank Collections by Digital Seed Image  Analysis
I.O. Daniel
Genotype discrimination of germplasm collections is an essential function of gene banks, enabling efficient delivery of genetic resources to researchers and the seed industry. Seed morphometric measurement by digital imaging analysis has been identified as a fast and reliable method for this task. In this study, 10 seed morphometric variables, namely seed length, seed width, seed thickness, seed diameter, seed area, embryo angle, shape factor, roundness factor, flatness index and circularity index were determined using captured seed images of 20 accessions of pepper (Capsicum annuum L.) landraces from germplasm collections

at the National Centre for Genetic Resources and Biotechnology (NACGRAB) gene bank, Nigeria. Digital seed metric data were subjected to principal components analysis. Shape factor, seed area, length, width, diameter, roundness factor and flatness index had the highest eigenvectors in the first principal component, which accounted for 72.9% of total variance. These variables thus constitute potential descriptors for cultivar discrimination of pepper seeds by digital imaging analysis. Single linkage clustering analysis based on seed size and shape metrics resulted in two major clusters and two minor clusters of the Nigerian pepper landrace collections. Such clusters constitute a classification tool for genotype discrimination when evaluating cultivar identity by seed metrics, and can thus improve management efficiency of genetic resources for pepper breeding.
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(pp. 193-202)
Soaking Solution Temperature, Moisture Content and Electrical Conductivity of Common Bean Seeds
Érica Fernandes Leão*, Rafael Marani Barbosa, Juliana Faria dos Santos and Roberval  Daiton Vieira
Initial seed moisture content (SMC) and temperature during seed imbibition can interfere with the electrical conductivity (EC) test results. This study aimed to evaluate soaking solution temperature and SMC on results of the EC test of common bean seeds. For this purpose, two experiments were conducted.

The first used five seed lots to determine the physiological potential and the initial SMC of seeds. The SMC of the lots was then adjusted to 9, 11, 13, 15 and 17%, and seeds subjected to the EC test. The second experiment used four seed lots to evaluate the effect of water temperatures of 10, 15, 20, 25 and 30 °C, before and during imbibition, on EC test results. The EC readings in the first experiment decreased as SMC increased from 9 to 17%, but these values tended to stabilize at SMC higher than 11%. In the second experiment, EC values increased with increasing imbibition water temperature, with the highest values and lowest vigor observed when seeds were imbibed at 30 °C. Therefore, the EC test for common bean seeds should be done with seeds at moisture contents between 11 and 15% and a temperature of 25 °C during seed  imbibition.
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(pp. 203-215)
Occurrence and Trends of Weed Seed and Pathogen Contaminants in Bentgrass Seed Lots in Oregon
Steve C. Alderman*, Sabry G. Thelias and Andrew G. Hulting
Nearly all of the bentgrass seed grown in the United States is produced in Oregon. However, little is known about the occurrence of weed seed or pathogen propagule contaminants in bentgrass seed lots. This study was conducted to assess the diversity and frequency of occurrence of weed seeds,

ergot (Claviceps purpurea), and seed galls (Anguina agrostis) in colonial (Agrostis capillaris L.) and creeping [Agrostis stolonifera L. var. palustris (Huds.) Farw.] bentgrass certified seed lot samples submitted to the Oregon State University Seed Laboratory during 1986–1995 and 2002–2010 for purity analysis. For colonial bentgrass, 115 different weed seed contaminants were detected, with 79 identified to species, 35 to genus and 1 to family. For creeping bentgrass, 60 weed seed contaminants were identified to species, 29 to genus, and 3 to family. The percentage of seed lots per year with no weed contaminants ranged from 13% to 50% and 47% to 84% for colonial bentgrass and creeping bentgrass lots, respectively, depending on year. The number of new weed seed contaminants in colonial and creeping bentgrass increased at a rate of 2.7 and 1.9 per year, respectively. During 2002–2010, the percentage of seed lots with ergot per year was 44–77% for colonial bentgrass and 16–30% for creeping bentgrass. Seed galls were found in 2–15% of colonial bentgrass seed lots, but were not detected in creeping bentgrass. This study revealed a wide and increasing diversity of weed seed contaminants in colonial and creeping bentgrass, and provided evidence of increasing ergot severity in colonial bentgrass.
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(pp. 217-226)
The Valve Method of Decanting Seeds from a Flotation Solution
Jacob E. Lucero*, Jeremy S. Payne and Brock R. McMillan
Enumerating seeds present in the soil is an element of many studies in disparate fields. Chemical flotation, in which target material is floated to the top of a liquid solution, is a common methodology for recovering seeds from the soil. Traditionally, target material is then decanted from the flotation solution by repeatedly skimming the surface with a net. However, this traditional method can be biased toward species with low relative densities.

This study reports on the development of a novel method of decantation—the valve method—and compares its performance to the traditional net-skimming methodology. Specifically, we compared effectiveness (proportion of seeds recovered from a known sample), rapidity (time required to decant that sample), efficiency (number of seeds decanted per second), and recovery bias (effect of relative density on seed recovery). We used each methodology to decant a flotation solution containing a known quantity of soil and seeds (20 replicates per method). Our proposed method was approximately 6% more effective, 425% more rapid, 447% more efficient, and significantly less biased than the traditional method. The differential results obtained using disparate decantation methods highlighted the importance of decantation in the flotation procedure and underscored the necessity of specifying the method of decantation used in any research employing chemical flotation. Any future work relying on flotation to analyze seed banks should clearly describe how samples were decanted and should consider the valve method as a potential means of enhancing the effectiveness and efficiency of chemical flotation.
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(pp. 227-242)
Pretreatment Effects on Germination and Vigor of Longleaf Pine (Pinus palustris) Seeds
Jill R. Barbour* and João P.F. Carvalho
Seed quality, prechilling and temperature affect longleaf pine (Pinus palustris Mill.) seed  cumulative germination and germination speed. Seedlots were grouped into germination classes according to seed quality based on their original laboratory germination, then subjected to different soak methods (water and benomyl), prechilling periods (0, 7, 14, 28,  42, 63 d) and germination temperatures (15, 20, 22, 25, 30 °C).

Seed quality and germination temperature explained 34% and 31% of cumulative germination variation, respectively, while prechilling explained 1.1%. For speed of germination, seed quality was less important (2.1%) than germination temperature (51%) and prechill factors (24%) in explaining variation. At 0, 7 and 14 d of pre -chilling, the best temperatures were 15 and 20 °C. Germination of poor quality seeds did not improve when prechilling exceeded 7 d. When germination class, prechill length and temperature were combined, high quality seeds responded best to prechilling of 14 to 28 d at optimal temperatures (15 to 22 °C). Highly vigorous seeds germinated in the first week following 28 d of prechilling, while low and medium vigor seeds required 42 or 63 d of prechilling. Seed vigor was negated with 42 d of prechilling. Germination speed was reduced from 13 d at 15 °C to 5 d at 30 °C, even though cumulative germination was lower. The best overall combination to maximize germination rate was 28 d of prechill at 22 °C to reach 50% germination in 7 d, with a final germination of 74.9%.
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(pp. 245-248)
Precision Seed Sorting to Improve Hybridity in Eggplant
Rakesh C. Mathad*, S.N Vasudevan, S.B Patil and B.L. Lokeshappa
Hybridity of a seed lot can be improved by precision seed sorting when seed sizes of the inbred lines vary significantly. In this study, eggplant (Solanum melongena L.) hybrid seed from a leading hybrid (No. 1461734) were used. Seed sizes of the male parent and the hybrid lots were comparatively bigger than the female parent.

The hybrid seed lot was subjected to a plant grow-out (PGO) test which showed that the hybrid seed lot was of low genetic purity. A physical purity test of the same lot showed that it contained 20% small seeds, which were then removed and effect of removal evaluated. The proportion of small seeds present clearly indicated the admixture of selfs in the hybrid seed lot. With the objective of removing these smaller seeds to improve hybridity of the seed lot, 10 different screen sizes were tried at the bottom of a gravity separator. Seed was sorted using a screen mesh size of 4.0 mm (round) on top, 3.5 mm (round) in the middle, and 10 variable sizes on the bottom. The 0.9 mm (slotted) bottom screen resulted in significantly higher hybridity (95.57%) when re-tested using the PGO test compared to other screen sizes and the control (81.00%).e 2.0 mm (round) mesh bottom screen significantly increased germination (79%) and usable transplants (76%) compared to other screens and the control (61 and 59%, respectively), and is the recommended screen size for sorting this hybrid compared to other bottom screen sizes and the control.
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(pp. 249-256)
Alternating Temperatures Promote Seed Germination of Miscanthus sinensis
Erik J. Christian* and A. Susana Goggi
Miscanthus sinensis can propagate through seed. However, there is little information regarding seed germination requirements. The objective of this study was to determine the optimal germination temperature requirements for the species. Seed germination was studied using a two-way thermogradient table without light.

The temperature gradient in the table had 30 cells with alternating day/night temperatures and 6 cells with constant temperatures. The constant temperature cells were 10, 16, 22, 28, 34, and 40 °C, and the alternating temperature cells were a combination of these same temperatures. Fifteen of the alternating temperatures were higher for 16 h and lower for 8 h. The other 15 alternating temperatures were higher for 8 h and lower for 16 h. Seeds exposed to alternating temperatures showed a higher germination percentage value than those at constant temperatures. The highest germination percentage was recorded in cells with a temperature combination of 16 °C for 16 h and 22 °C for 8 h. These results are important to seed analysts developing a standard germination protocol for Miscanthus sinensis seed.
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(pp. 257-262)
Influence of Ultraviolet Light on Germination Capacity of Kentucky Bluegrass
E.J. Nangle, D.S. Gardner*, M.A. Bennett, T.K. Danneberger, J.D. Metzger and L.E. Rodriguez-Saona
Kentucky bluegrass (Poa pratensis L.) is a commonly used turfgrass in the temperate climates of the United States. The grass is predominantly established from sod because of its slow germination (21 d). Ultraviolet (UV) light has been noted to enhance germination speed of other crops and it may similarly enhance Kentucky bluegrass germination.

Turfgrass seeds from two seed lots were placed in two separate germination chambers and set on an 8 h light/16 h dark schedule. One chamber received only visible light while the other received a supplemental UV light treatment (11.2 kJ m−2 d−1). The treatments were applied for 21 d. Seed germination was counted at 7, 14 and 21 d. Ultraviolet light increased germination capacity and speed in the newer but not older seed lot. Seed germination was greater (p ≤ 0.05) at day 7, and after 21 d germination was higher in UV light conditions than in control. These results suggest that treatment of bluegrass seed with UV light may enhance germination, although seed age may override the effect.
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(pp. 263-272)
Evaluating Sunn Hemp (Crotalaria juncea) Seed Viability Using the Tetrazolium Test
Clíssia Barboza da Silva*, Rafael Marani Barbosa and Roberval Daiton Vieira
The tetrazolium (TZ) test is a quick and potentially precise method for estimating seed viability. However, its efficiency depends on adapting the methodology for each species. The objective of this study was to determine the best seed preparation methodology for TZ testing of sunn hemp (Crotalaria juncea L.) seeds, as well as establish staining patterns for estimating seed viability.

Four seed preparation methods were studied for staining: seed coat removal; longitudinal cross-section cut through the embryonic axis without seed coat removal; longitudinal cut in the distal region of the embryo axis, from the thick-end of the seed through the cotyledons; and transversal cut in the distal region of the embryo axis, across the seed width through the cotyledons. Of the preparation methods studied, the most promising was seed coat removal. Staining patterns of seeds prepared in this manner could be easily classified into three classes. Class 1 included viable, vigorous seeds, class 2 included viable, non-vigorous seeds, and class 3 included nonviable seeds. Therefore, the TZ test with seeds prepared by removing the seed coat is a promising alternative for identifying possible causes of seed viability loss in production systems.
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(pp. 275-282)
Topographischer Nachweis der Keimfähigkeit der Getreidefrüchte durch Tetrazoliumsalze (Topographic Detection of Germination in Cereal Crops by Tetrazolium Salts)— A Translation of Lakon’s 1942 Paper on Tetrazolium Seed Testing
Michael Witty
This article is a translation of Lakon’s paper published in 1942, which is still cited but inaccessible to most scientists. Lakon’s paper was a significant milestone in the history of botany and provided technical descriptions of experiments which are still relevant today.

Live seeds and dead seeds are often indistinguishable using the unaided eye. is paper describes the origin and useful technical details about topological seed testing using the vital stain 2, 3, 5-triphenyl-tetrazolium-chloride (tetrazolium testing), which have previously had very limited circulation. is is because the research was originally published in a minor regional journal which, to complicate matters, suffered from reduced circulation during the 1939–1945 world conflict. The culture of science also changed after 1945, and while it was common for prewar research to be published in German, modern botanists today prefer to publish technical manuscripts in English.
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