Volume 22, No. 1, 2000

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(pp. 5-14)
Reevaluation of Tolerances for Noxious Weed Seeds
S. G. Elias, H. Liu, O. Schabenberger, and L. O. Copeland*
This paper examines the background and validity of the current noxious weed seed tolerances used by the Association of Official Seed Analysts and tolerances for counts of other seeds used by the International Seed Testing Association. The effects of the two types of statistical errors (Type I and II), their relationship to sample size, and their impact on both the seed seller and consumer are discussed.

This study suggests that the formula for the normal approximation of the Poisson distribution used to calculate the present AOSA noxious weed seed tolerances in the AOSA Rules for Testing Seeds is in error. Furthermore, probabilities of the Poisson distribution can be derived directly without the need for the approximation for a wide range of means (average number of noxious weed seeds). Alternative tolerances are suggested based on appropriate statistical procedures. The problem of a zero standard for prohibited noxious weed seeds is discussed. No statistical basis or special tolerance exists for enforcement of labeling information for seeds of “undesirable agricultural species.”
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(pp. 15-22)
Hidden Fluorescence in the Seedling Root Fluorescence Test of Ryegrass
R.E. Barker*, S.K. Davidson, R.L. Cook, J.B. Burr,
L.A. Brilman,M.J.McCarthy, A.E. Garay, andW.D. Brown
The seedling root fluorescence (SRF) test has been used in the USA since 1941 to distinguish annual or Italian ryegrass (Lolium multiflorum Lam.), which generally has root fluorescence under ultraviolet light, from perennial ryegrass (L. perenne L.), which does not. The objective of this study was to determine the contribution to crop kind separation from seedlings with fluorescence hidden under the seedling root.

Roots of 63,996 seedlings were examined from 11 perennial ryegrass cultivars. Inflorescence formation was used to verify annual types. Hidden fluorescence was never observed in annual ryegrass check cultivars. Thus, the characteristic appears to be a phenomenon only of perennial ryegrass. Seven plants out of 480 seedlings with bright fluorescence produced a reproductive inflorescence in growout tests, but only one out of 418 seedlings with hidden fluorescence headed out. We concluded that hidden fluorescence did not contribute significantly to detection of contamination from ryegrass plants that flower without vernalization (annuals). Further, adding hidden fluorescence seedling counts to total counts adds additional variation to SRF test results. Simplification of the SRF test by eliminating the need for lifting each seedling to verify hidden fluorescence expression will save testing time by seed technologists, and that will reduce testing costs and avoid marketing delays.
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(pp. 23-33)
Germination and Vigor Response to Seed Maturity, Weight, and Size Within the Virginia-type Peanut Cultivar, VA-C 92R
J. F. Spears
Commercial seed lots of large-seeded virginia-type peanut (Arachis hypogaea L.) consist of a wide range of sizes and maturities. Determining how seed size and maturity affect germination and seed vigor is important in helping growers establish optimum plant stands. Research was initiated to determine the effects of seed maturity, size, and weight on germination and vigor.

Pods from the peanut cultivar ‘VA-C 92R’ harvested in 1993 and 1994 were separated into maturity classes based on hull mesocarp color. Maturity classes included yellow (YE), orange (OR), brown (BR), and black (BL), with BL being mature pods containing seeds at physiological maturity. Seeds within each maturity class were separated by size using a series of slotted screens consistent with those used in the seed industry. Seed weight, germination, and vigor increased as seed maturity increased when seeds of a common size were compared across maturity levels. When seeds of a common maturity were compared across sizes, seed weight increased for all maturity levels in both years; seed germination increased for seeds from YE, OR, and BR pods in 1993 and for YE and OR pods in 1994. Seed vigor increased for seed from YE,OR, and BR pods in both years.At physiological maturity, seed size did not affect germination or vigor. These data suggest seed size and weight influence peanut seed quality.Germination and vigor from seeds with similar size and weight were greatly influenced by maturity level.
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(pp. 34-42)
Alternative Residue Management and Stand Age Effects on Seed Quality in Cool-season Perennial Grasses
Thomas G. Chastain*, William C. Young III, Carol J. Garbacik, Paul D.Meints, and Thomas B. Silberstein
Field-burning based management of crop residue after seed harvest has been an important but controversial component of the production of cool season perennial grass  seed crops. On-farm trials were conducted in 26 commercial seed fields to examine the effect of residue management practices and stand age on seed quality. Species tested included:

perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.), creeping red fescue (F. rubra L.), Chewings fescue (F. rubra spp. commutata Gaud.), orchardgrass (Dactylis glomerata L.), and dryland bentgrass (Agrostis castellana Boiss. and Reut.). Residue management treatments included: (i) flail chopping with no straw removal (Straw), (ii) removal of straw by baling with or without further management of stubble (Bale), (iii) removal of straw by baling, followed by propane burning (Propane), and (iv) open-field burning (Burn). Growing cool-season perennial grass seed crops without open-field burning did not reduce seed purity or germination. Straw management without removal in Chewings fescue decreased purity and caused reduced seed germination. Seed purity was lower in older stands of perennial ryegrass, but tended to be higher in older stands of tall fescue. Seed germination was not consistently related to age of crop stand. Reduced seed purity was often accompanied by increased inert matter and sometimes by lower seed germination. Cool-season perennial grass seed growers can generally adopt alternative residue management practices without compromising seed quality.
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(pp. 43-55)
Determination of High Seed Moisture in Maize
Shande Tang, D.M. TeKrony*,M. Collins and C.McKenna
Corn (Zea mays, L.) seed moisture content is commonly used as an indicator of seed maturity. The objectives of this study were to determine seed moisture at various stages of corn seed development using a microwave oven and relate these results to several other methods for determining seed moisture. Two genotypes were harvested frequently during seed development and seed moisture was determined by two microwave methods;

microwave (intact seed) and microwave (ground seed) and three other methods: oven [intact seed (105 °C, 48 and 72h), oven ground seed (130 °C, 4h)] and DICKEY-John meter.Methods were compared by analyzing seed samples removed from the mid-section of ten ears harvested at four-day intervals from 31 to 87 days after pollination. The oven (ground) method was the most accurate even though less convenient because of grinding. The most accurate oven (intact seed) method was after drying for 72 hours at 105 °C. The DICKEY-John meter measurement of moisture was more variable, especially at seed moisture > 30%. Regression analysis showed an excellent linear relationship (r2 =0.98) between the weight loss of ground seed following microwaving (microwave, ground method) and oven (intact) seed moisture across all harvest dates and both genotypes. The microwave (intact) method showed a more variable relationship (lower r2 values) between weight loss and seed moisture. A model was developed to estimate seed moisture content based on weight loss using the microwave (ground) method. These results show that the microwave oven can provide a fast (~60min.) estimate of weight loss for high moisture corn seed, which can be used to accurately estimate seed moisture.
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(pp. 59-63)
Comparison of Two Methods of Purity Testing for Festuca pratensis Hudson and Lolium x hybridum Haussknecht
Deborah J. Lionakis Meyer
Comparisons among the AOSA purity testing methods for meadow fescue (Festuca pratensis Hudson) and intermediate ryegrass (Lolium x hybridum Haussknecht), and a new method in which only the large sterile structures are removed were made by the AOSA Purity Subcommittee. Pure seed percentage, number and types of seed unit attachments, amount of inert material recovered from the attachments and the time required for inert recovery were examined. The new method produced nearly identical purity results to the AOSA method for both species with a considerable time savings.
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(pp. 64-68)
The Effect of Replicate Size on Germination of Glycine max and Vigna unguiculata subsp. unguiculata
Aida Rosa Galarza
This referee evaluated seed spacing frequency on the standard germination test for two moderate quality soybean [Glycine max (L.) Merr.] lots (80% germination), one high quality (90%) and one low quality (67%) cowpea (Vigna unguiculata subsp. unguiculata) lot. Samples were sent to 27 laboratories with specific instructions to germinate each sample in three concurrent 400 seed tests by varying spacing using 25, 50, and 100 seeds per replicate.

Three different germination towel sizes, 10"x15", 12"x16" and 10"x30" were identified among participating laboratories. Twenty-two laboratories participated in the soybean referee. Improved germination was observed for both soybean lots with increased seed spacing. The greatest improvement was observed in the smallest towel size group (10"x15"). Nineteen laboratories participated in the cowpea referee. Improved germination was noted for both low and high quality seed lots in the smallest towel size group. The low quality seed lot demonstrated themost benefit fromincreased seed isolation. The larger towel size groups (12"x16" and 10"x30") showed limited improvement in germination with increased replicate size. Thismay be due to already improved seed spacing at those levels. Laboratories using smaller towel sizes might consider seed spacing at the 25 seed per replicate level, especially for low quality seed lots. Future germination referees should consider towel size used by laboratories since it may influence germination results.
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(pp. 69-73)
Leakage of Solutes from the Germinating Seeds of Pisum sativum, as Influenced by Thiamin
A. Ahmad*, S. Hayat and Shazia Khan
The seeds of Pisum sativum (L.) cv. Arkil were soaked in graded concentrations (10-9, 10-7, 10-5 and 10-3M) of thiamin (Vitamin B1), for 3 hours. The seeds pre-treated with 10-9M of the vitamin leaked lesser quantities of proteins, saccharides, nitrogen and phosphorus and exhibited higher germination percentage, than the control.

However, the rate of leakage increased and the per cent germination decreased as the vitamin content was increased. At the highest thiamin concentration (10-3M), the loss of solutes from the seeds was significantly higher and the germination decreased by about 30%. The electrical conductivity of the medium increased with an increase in the leakage of the electrolytes. An inverse relationship between per cent germination and leakage of the solutes was noted.
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