Volume 27, No. 2, 2005

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(pp. 177-189)
Effect of High Temperature Stress During Different Stages of Seed Development in Soybean [Glycine max (L.) Merrill]
D. B. Egli,* D. M. TeKrony and J. F. Spears
Soybean [Glycine max (L.) Merrill] plants were grown in controlled environments to evaluate the effect of high temperature (38, 33 °C) stress on standard germination (SG) and vigor [accelerated-aging germination (AA) and electrical conductivity]. Initially, the effect of changing the standard temperature cycle in the phytotron from 10 and 14 hours at the maximum and minimum temperatures to a cycle that mimicked the sinusodial field temperature cycle (maximum temperature did not change) was evaluated.

The  maximum temperature of 38 °C reduced SG and vigor for soybean cultivars ‘Hutcheson’ and ‘McCall’, while only vigor was reduced at 33 °C, just as in the standard cycle. Secondly, the effect of short exposures to high temperature at various intervals during seed development was evaluated. Plants were moved to the growth chamber at weekly intervals during seed filling and returned to the greenhouse after a 7- or 14-day exposure to 38/27 °C. Exposure for 7-day periods during seed development did not affect SG and caused only small reductions in AA. Fourteen-day exposure periods caused larger reductions in SG (maximum reduction of 32 percentage points) and AA (maximum of 62 percentage points) when high temperatures occurred later in seed development, but had no effect early in development. The quality of seeds that matured (pods turned yellow or brown) during the high temperature treatment was the same as seeds that matured after treatment (pods were green at the end of treatment). High temperature represents another stress in addition to disease infection and mechanical damage, which can reduce soybean seed quality during seed production.
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(pp. 190-202)
A Computer-based System for Seed Identification
T. Daoust,* Fujimura, M. B. McDonald and M. A. Bennett
An image processing computer application was developed to collect statistics of physical characteristics from seeds. A machine learning technique ensured that the software was applicable to a wide variety of species so that it could be used in purity analysis tests. The method presented requires an inexpensive scanner and a modern personal computer. The software operates by locating seeds within the digitized image of the purity sample and takes measurements on each seed (width, height, area, perimeter, average color, etc.).

These measurements are inputted into a classification routine trained to recognize all potential seeds within the sample. The classification routine determines the closest matching species for each seed in the image and reports the results to the user. Because of the wide variation in seeds encoun- tered in purity tests, the automated system of measurement and classifica- tion is highly configurable. The seed identification system is designed to be rapidly adapted to specific seed types and trained without knowledge of artificial intelligence techniques.
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(pp. 203-210)
Germination of Switchgrass under Various Temperature and pH Regimes
D. Hanson* and H. A. Johnson
Switchgrass (Panicum virgatum L.), a native prairie grass, is being increasingly used as a biomass energy crop. To determine optimal conditions for germination, the effect of temperature and pH were studied using several switchgrass cultivars.

Seeds of eight cultivars were germinated at five temperatures and nine pH levels. The optimal conditions for germination were found to be 25 °C with a substrate of pH 6.0. The data indicated that germination occurs relatively well in substrates with pH values ranging from 6–8 if the temperature is within 25–35 °C. The interaction between pH and temperature provides strong management implications. For optimum stand establishment in the field, switchgrass should be planted in warm soils with a pH range of 5–8. These results indicate that switchgrass establishment in soils with pH values outside this range may not be successful.
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(pp. 211-222)
Detection of the CaMV-35S Promoter Sequence in Maize Pollen and Seed
Higinio Lopez-Sanchez, A. Susana Goggi* and Rai Satish
This study developed an extraction protocol for pollen DNA in corn, and screened current and new primers designed to detect the CaMV35S promoter in corn pollen and seed. Bt transgenic and non-transgenic corn hybrids were used to obtain the seed and pollen DNA. Polymerase Chain Reaction (PCR) and gel electrophoresis were used to evaluate the efficacy of the pollen DNA extraction protocol, and to test the efficiency of 11 primer pairs in detecting the CaMV35S promoter sequence. 

The DNA extraction method described here was very successful in releasing the DNA from pollen grains, as determined by the intensity of the 18 bands of genomic DNA samples amplified with the HMG-AF1/HMG-AR1 corn-specific primers. The strong intensity of the bands formed by primers P35S1/P35S2, P35SA/P35SB and P35S-aflu/P35S-ar1 showed these primers were the most efficient in amplifying transgenic pollen DNA; whereas, primers P35S1/P35S2 generated the strongest band intensity in seed DNA. The new primers 35S168F/ 35S317R showed higher sensitivity in detecting the CaMV35S promoter than any other primer included in this experiment. The proposed pollen DNA extraction method and the primer 35S168F/35S317R were very effective in extracting DNA from pollen samples and identifying the CaMV535S promoter sequence in transgenic varieties.
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(pp. 223-229)
Viability, Metabolic Heat and Respiration Rates of Paclobutrazol Treated Verbena and Marigold Seeds
Stanislav V. Magnitskiy, Claudio C. Pasian,* David W. Burger, Mark A. Bennett and James D. Metzger
This study was undertaken to determine whether soaking marigold (Tagetes patula L.) or verbena (Verbena X hybrida Voss.) seeds in various concentrations of paclobutrazol solution reduces the level of seed metabolism and seed viability.

Tetrazolium tests demonstrated that verbena seeds soaked in solutions of 50–500 mg · L–1 paclobutrazol were viable. Verbena or marigold seeds soaked in solutions of 10–500 mg· L–1 paclobutrazol had lower respiration and heat production rates than controls. These lower respiration rates were not found in washed verbena or marigold seeds suggesting that paclobutrazol had been leached from the seeds. Lowering seedling emergence in verbena with increasing paclobutrazol concentrations and corresponding inhibition of CO2 emission rates indicated that paclobutrazol imposed dormancy in verbena seeds.
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(pp. 230-239)
Identification of Prosopis L. Seeds Using High Performance Liquid Chromatography
Glenn W. Freeman* and Jeremy L. Snyder
Seed storage proteins of thirteen species of the genus Prosopis L. were investigated by reversed-phase high performance liquid chromatography (RP- HPLC). The resulting chromatograms demonstrated that the species studied could be separated into three classical taxonomic sections previously established by plant morphology.

Individual species showed enough variation to be accurately identified based on their respective chromatograms, except for P. glandulosa Torr var. glandulosa, P. glandulosa var. torreyana (L. D. Benson) M. C. Johnst., and P. velutina Wooton. Peak retention time ratios to a reference peak were used to identify individual peaks. The presence or absence of these peaks allowed for identification of individual species. A synoptic key was devised to help interpret the chromatograms. Protein analysis by RP-HPLC appears to be a quick and easy method for species identification within Prosopis and should be a useful tool to plant biologists and seed analysts as an aid to species identification.
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(pp. 243-247)
Moisture and Temperature Effects on Maize and Soybean Seedlings Using the Seed Vigor Imaging System
R. Otoni* and M. B. McDonald
Fast and reliable results from seed quality tests are essential for producers. The Seed Vigor Imaging System (SVIS) was developed to improve assessment of seed quality. This study had the objective of identifying the optimum paper towel moisture contents and temperatures for maize and soybean seed germination during a three-day test period.

Seeds were planted on paper towels with seven different moisture contents for maize and eight for soybean. Three different temperatures (24, 25 and 26 °C) were used for germination of the two crops. Decreased speed of growth and overall vigor indices were observed when the moisture content of the paper towels had less than 96% saturation in maize and 79% saturation in soybean. When the germinator temperature varied 1 °C less than 25 °C, no difference was detected in the SVIS indices. However, a difference of 1 °C more than 25 °C caused a significant increase in seedling growth. These results demonstrate the importance of monitoring paper towel moisture contents used for the SVIS test, particularly for maize seeds, and show that moisture and temperature variables must be carefully controlled during standard germination and vigor tests to assure standardization of reported results.
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(pp. 251-261)
Asteraceae: Determination of the Pure Seed Unit
Susan Alvarez*
The pure seed unit as applied in seed purity analysis is poorly defined and difficult to determine for many native species belonging to the Asteraceae. This paper reviews the history of the pure seed unit for Asteraceae as defined in the Association of Official Seed Analysts’ Rules for Testing Seeds from 1955 to the present.

In the 1950s, only eight Asteraceae species were listed in the AOSA Rules and these were widely cultivated and highly milled due to their thick, opaque fruit walls. However, there are now at least 90 species of Asteraceae listed in the AOSA Rules and these taxa are not highly cultivated or milled. Furthermore, the pure seed unit definitions have fundamental differences between the AOSA, ISTA and the Canadian purity methods. Recently, Artemisia tridentata has been studied to determine an accurate pure seed unit definition. It is important to promote such work to foster standardization of the pure seed unit as it applies to the large number of species in the Asteraceae.
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(pp. 262-265)
Seed Dormancy— Where Do We Go Now?
Gil Waibel
This article presents an evolution of seed dormancy testing as published in the AOSA Rules for Testing Seeds over the years, and thoughts about the future of dormancy testing. The most important question is whether dor- mancy testing is needed, and, if so, how? This article is not an endorsement of a technique, but it is an attempt to stimulate thought and efforts toward re- evaluating how we test seed lots containing dormant seeds, and finding better ways to test these seed lots.

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(pp. 269-272)
A Single Nucleotide Polymorphism Linked to the Quantitative Trait Locus of Soybean Cyst Nematode Resistance
Huabang Chen, Jamal Faghihi, Virginia Ferris, Pam Hogue, Karen Miller and Rick Vierling*
We previously mapped four unlinked restriction fragment length polymorphism (RFLP) markers associated with soybean cyst nematode (SCN) resistance. The partial coefficient of determinations (R2) of the major quantitative trait locus (QTL) A006 is 91%. A single nucleotide polymorphism (SNP) linked to the major QTL of soybean cyst nematode resistance was detected by comparing sequences amplified from “Hartwig,” a broad-based SCN resistant line, and “Williams 82,” an SCN susceptible line. The SNP was validated using SCN bioassay data at Purdue University. This SNP is located within the site of Fau I, which makes it possible to distinguish resistant allele T from susceptible allele C by PCR followed by Fau I digestion. The discovery of this SNP and its easy detection are of significant importance to plant breeders and to quality assurance managers.

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(pp. 273-285)
Vigor Tests for Evaluating the Performance of Argentine Canola (Brassica napus L.) under Different Growing Conditions
H. Elliott,* L. W. Mann and O. Olfert
Experiments were conducted in 1998–2000 to develop vigor tests for evaluating the performance of Argentine canola, Brassica napus L., under different growing conditions. Seed lots were evaluated annually in 5–7 seed laboratories using the standard germination test (SGT) and prehill test (PCT). Germination was assessed after 7 d in the SGT and after 11 or 12 d in the PCT.

The vigor index of seed lots was calculated by multiplying the 1000- seed weight by percent germination/100. Seed lots were evaluated annually at 3–6 locations. Seeds were planted into warm dry soil in 1998, cool moist soil in 1999 and cool dry soil in 2000. Statistical correlations and linear regression were used to identify seed attributes that provided the best indication of seedling establishment, shoot weight and biomass. In all field trials, germination in the SGT and PCT was strongly correlated with seedling establishment and poorly correlated with shoot weight. Establishment improved as germination increased. Germination in the SGT and PCT provided an equally good indication of establishment in warm soil and cool soil. Thousand-seed weights were poorly correlated with establishment and strongly correlated with shoot weights. With a 1.0 g increase in seed weight, shoot weights increased by 105 mg in warm soil and by 18–50 mg in cool soil. Vigor indices of seed lots in the SGT and PCT were highly correlated with biomass in all field trials. With a 1.0 unit increase in the vigor index, bio- mass increased by 1.4–1.6 g/m-row in warm soil and by 0.4–1.1 g/m-row in cool soil. Vigor indices in the PCT provided the best indication of biomass in warm and cool soils.
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