(pp. 7-18)
Seed Moisture and the Equilibrium Seed Moisture Content Curve
Miller B. McDonald*
ABSTRACT:
Seed moisture content constantly changes in relationship to the temperature and relative humidity of the air surrounding the seed. Because seed moisture content is important in determining seed longevity and many other aspects of seed quality, this report emphasizes the properties of water, the types of water bonding in a seed, and how water is attracted to seed compounds.
These relationships are examined with respect to various phases found in equilibrium moisture content curves (isotherms) for seeds. Understanding these factors permits greater insights into seed physiology and performance.
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(pp. 21-36)
Vigor Tests for Evaluating Establishment of Canola under Different Growing Conditions and Tillage Practices
R. H. Elliott,* L.W.Mann, E. N. Johnson, S. Brandt, C. Vera, H. R. Kutcher, G. Lafond and W. E. May
ABSTRACT:
Experiments were conducted to develop vigor tests for evaluating the establishment of open-pollinated Argentine canola, Brassica napus L., in conventional tillage (CT), minimum tillage (MT) and zero tillage (ZT). Sixteen seed lots of an open-pollinated cultivar were produced from swathing experiments in 2000 and 2001. Seed lots were assessed in 2003 in the standard germination test (SGT), accelerated aging test (AAT), controlled deterioration test (CDT), pre-chill test (PCT) and electrical conductivity test (ECT). Green seed content and 1000-seed weight were also determined. Establishment of the seed lots was evaluated at three sites with CT, two sites with MT and one site with ZT.
The six sites also differed in soil texture and rainfall. Establishment averaged 75–79% in CT, 42–56% in MT and 17% in ZT. Establishment was lowest at sites with reduced tillage, heavy-textured clay and below-average rainfall. Thousand-seed weights, along with germination in the SGT, AAT, CDT and PCT were positively correlated with establishment in CT and MT but not in ZT. Depending on the site, establishment improved by 8–11% with each 1.0 g increase in 1000-seed weight. Germination in the SGT, AAT and CDT provided a better indication of establishment in CT and MT than germination in the PCT. Establishment improved by1.4–2.4% with each 1.0% increase in germination in the SGT.
Green seed content and conductivity were negatively correlated with establishment at all sites. Establishment declined 2–3% with each 1% increase in green seed and 10 μS cm–1 g–1 increase in conductivity after soaking seeds for 24 h. Conductivity after 4 or 24 h soaking provided the best indication of stand establishment at most field sites. The effects of swathing time on the quality, germination and vigor of canola seed lots are also discussed.
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(pp. 37-49)
A Rapid and Inexpensive Test for Determining Optimal Hydrothermal Timing for Priming Lettuce Seed
Jennifer R. Bonina, Daniel J. Cantliffe,* Peter J. Stoffella, and Donald J. Huber
ABSTRACT:
The requirements for and results from priming lettuce seed can vary according to age, vigor, and thermosensitivity of the seed. This investigation determined the optimal hydrothermal timing for priming lettuce seeds, independent of cultivar, seed lot, and storage using an inexpensive gel assay for the enzyme endo-β-mannanase (EBM). Two lettuce cultivars ‘Bennett’ and ‘Connick’ and two seed lots of each were used.
Seeds were primed in an aerated –1.2 MPa polyethylene glycol 8000 (PEG) solution at 15 °C in constant light, and were sampled at 24 h, 48 h, or 72 h. Enzyme activity for each lot at each priming duration was determined by a single-seed gel assay for EBM. At 36 °C, germination of primed seeds was over 90%, while non-primed seeds germinated at 40%. EBM activity was non-detectable in dry seeds and in less than 5% of the seeds primed for 24 h. After priming for 48 h or 72 h, 30% or more of the micropylar section of the whole seed exhibited EBM activity, regardless of seed lot or cultivar. Since the percentage of seeds exhibiting EBM in the whole endosperm after 48 h or 72 h of priming were similar but total percent and rate of germination at 36 °C were optimal after 48 h of priming, 48 h was considered the optimal hydrothermal priming time. EBM activity was observed in 25% of seeds at 48 h priming duration. Therefore, it was proposed if at least 25% of seeds exhibit EBM activity, optimal hydrothermal time is achieved. The EBM test was estimated to cost $11.56 per 1000 seeds. This price does not include facilities or equipment costs. Determining priming time with the EBM test provides a method to improve optimization of the priming procedure for endospermic seeds such as lettuce.
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(pp. 50-59)
Genetic Variability in Phaseolus spp. as Revealed by SDS-PAGE Markers
R. H. Sammour,* S. A. Radwan and A. El-Koly
ABSTRACT:
Seed proteins for five species (Phaseolus vulgaris, P. acutifolius P. grayanus, P. lunatus and P. maculatus) were analyzed electrophoretically to assess genetic diversity between and within these species. A total of 31 subunits were resolved by SDS-PAGE. Each of the analyzed samples had a unique profile, although a few subunits were highly conserved.
Analytical results of SDS-PAGE of seed protein demonstrated the plausibility of the SDS-PAGE marker system for organizing genetic diversity in the genus Phaseolus. It revealed the genetic relation between P. lunatus and P. maculatus and confirmed their monophyletic origin. It also showed the broad genetic diversity in P. acutifolius germplasm and suggested a gene flow among the parental entities of its accessions. Jaccard similarity index, cluster analysis and factor analysis revealed that P. grayanus had a high polymorphism with P. lunatus and P. maculatus, and P. acutifolius respectively, suggesting unidirectional introgression among them. The genetic distance between P. vulgaris and other species is discussed.
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(pp. 60-67)
Use of ELISA to Differentiate between Toxic and Non-toxic Endophytes in Tall Fescue Seeds
Simone Trento, Sabry Elias,* and Adriel Garay
ABSTRACT:
The fungal endophyte Neotyphodium coenophialum is known to enhance tolerance to biotic and abiotic stresses in grasses. However, most endophyte infected fescue contains toxic ergot alkaloids, which can induce a fescue toxicosis syndrome when consumed by ruminants and horses. Recently, new tall fescue cultivars infected with endophyte strains that do not produce toxic ergot alkaloids have been developed. The objectives of this study were to determine whether a commercially available ELISA kit for detecting ergot alkaloid (ergovaline) in plant tillers would detect alkaloids in tall fescue seeds, to determine whether mechanical scarification or crushing of tall fescue seed would facilitate alkaloid detection by ELISA, and to determine whether ergovaline alkaloid detection by ELISA was consistent with the HPLC method.
Cultivars included in the comparison were Jesup MaxQ, a proprietary tall fescue cultivar containing endophytes that do not produce ergovaline, and KY-31, a conventional cultivar containing endophytes that produce ergovaline. Seed lots of Jesup MaxQ and KY-31 had similar endophyte infection rates of 90% and 94%, respectively, as measured by the microscopic method. Percentage seeds with ergovaline in scarified, crushed, and whole seeds were 87.5%, 91%, and 7.5%, respectively, for KY-31, and 0.5%, 0.5%, and 0%, respectively, for Jesup MaxQ, based on ELISA. The ergovaline concentration of Jesup MaxQ was <10 ppb compared to 5290 ppb in KY-31 as determined by HPLC. The results of this study indicate that the ELISA kit was a viable alternative to HPLC for detecting the presence of ergovaline producing endophytes in tall fescue seeds. Scarifying or gently crushing the seeds were suitable techniques for extracting alkaloids from seeds.
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(pp. 68-75)
Effects of Seed Size, Sowing Orientation and Depth on Germination and Seedling Growth in Neem, Azadirachta indica
A. K. Uniyal,* Bhupendra Singh and N.P. Todaria
ABSTRACT:
Seed germination and seedling growth of A. indica were affected by seed size and seeding depth. Large seeds germinated earlier with 95% total germination compared to small seeds with only 57% germination. Also, longer shoot-root lengths were observed in plants from large seeds.
In seed orientation uniform germination and seedling growth were recorded. No significant impacts was recorded in different seed orientation on seed germination as well as seedling growth. Seedling morphology did not differ much among treatments. Similarly, seeds sown in the upper soil layer germinated more rapidly and proved better growth compared to sowing at 3 and 5 cm depths. Mean germination time, germination index, shoot and root growth, root collar diameter and number of leaves followed the similar pattern.
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(pp. 76-84)
Osmotic and Cold Treatments Prior to Drying on Germination of Common Vetch during Maturation
Nezar H. Samarah*
ABSTRACT:
The germination capability of freshly (before drying) harvested seeds of common vetch (Vicia sativa L.) was improved by air-drying when seeds were harvested at or after seed physiological maturity. Low osmotic potential may substitute for air-drying to improve seed germination. Field and laboratory experiments were conducted to study the effect of low osmotic potential or cold treatments prior to ambient-drying on seed dormancy and germination of common vetch seeds harvested at different maturity stages.
Pods were harvested at four stages of maturity: 1) full-size (FS) seeds, 2) greenish-yellow (GY) pod, 3) yellow (Y) pod, and 4) brown (B) pod. At each maturity stage, freshly harvested seeds were exposed to three drying treatments for 4 d prior to air-drying at ambient conditions: 1) low osmotic potential (–1.2 MPa; osmotic), 2) air-drying at 5 °C (cold), 3) air-drying at ambient conditions (24 ± 2 °C; ambient). Seed standard germination was measured on freshly harvested seeds and 4 d after imposing the drying treatments. Osmotic treatment improved seed germination at 4 d compared with the cold and ambient treatments for seeds harvested at the GY, Y, and B stages. Osmotic treatment improved seed germination of air-dried seeds at the Y stage. The germination of the air-dried seeds was higher than those seeds dried for 4 d at ambient or cold temperature, suggesting that air-drying was a prerequisite for improving seed germination. However, the osmotic treatment improved seed germination without the need for air-drying when seeds were harvested at maturity(brown pods), due to the reduction in dormant seeds.
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