Volume 39, No. 1, 2018

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Download abstracts (free download) from oral and poster presentations given at the 108th Association of Official Seed Analysts and the 95th Society of Commercial Seed Technologists (AOSA/SCST) annual meeting held in Raleigh, North Carolina on June 1-8, 2018.

(pp. 7-24)
Radio-Frequency Electrical Seed Treatment to Improve Germination: A Review
Stuart O. Nelson
An historical background on electrical treatment to improve seed germination and seedling performance is presented. Studies on use of radio-frequency (RF) dielectric heating for increasing germination through reduction of hard-seed percentages, i.e., increasing seed-coat permeability to water, are reviewed.

Extensive studies on treatment of alfalfa seed with RF electric-field exposures for increasing germination through hard seed reduction and examination of seeds to explain effects of treatment are summarized. The influence of frequency, electric field intensity, seed moisture content, seed temperature, varietal variation and other factors are discussed, and aspects of practical application in the seed industry are considered. Experiments with RF treatment of seeds of sweetclover, other small-seeded legumes, cereals, vegetables, pine, and other woody plants and trees are also summarized.
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(pp. 25-34)
Mechanical Scarification Improves Seed Germination of Enterolobium cyclocarpum, a Valuable Neotropical Tree
Ana Salazar and Claudia Ramírez
Improving seed germination of native species is fundamental in aiding conservation and restoration practices, particularly for endangered ecosystems.  Seasonally dry tropical forests (SDTF) of Central and northern South America are among the most endangered ecosystems worldwide.  Enterolobium cyclocarpum, a distinctive legume tree species in SDTF, is widely used in restoration practices due to its extensive canopy and nutrient-rich leaves and fruits. 

However, seeds of this species exhibit low germination as a result of physical dormancy, limiting propagation on a large scale. In this study, we evaluated the effects of different pre-sowing treatments with the purpose of improving the germination of E. cyclocarpum seeds, to assist in largescale propagation programs of this valuable species. Specifically, we evaluated the effects of mechanical scarification, immersion in hot water (92° C for 2 min), and imbibition at room temperature of scarified and intact seeds.  Mechanical scarification with sandpaper and seed immersion in hot water improved final percentage germination and germination rate, while intact seeds germinated poorly (3%). Mechanically-scarified seeds, however, had higher germination (88%) than seeds immersed in hot water (40%). Soaking seeds in water at room temperature did not further improve germination of scarified or intact seeds. Our results indicated that mechanical scarification can significantly improve large-scale propagation of E. cyclocarpum, assisting in habitat restoration and conservation practices of degraded Neotropical ecosystems, such as seasonally dry forests.
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(pp. 35-52)
Soybean Seed Hormo-Priming Response to Gibberellin and Ethephon in Combination with  the Antioxidant N-Acetyl-L-Cysteine
Raman Manoharlal and G.V.S Saiprasad
Seed priming is a method to improve the germination performance of seeds.  Hormo-priming with gibberellin A3 (GA3) and ethephon (ET) has been shown to promote germination and antioxidant capacity of soybean seeds.  However, no systemic studies have been carried out to determine hormo-priming effects of GA3 and ET, in combination with antioxidants, on soybean seed/seedling germination and development indices.  This laboratory investigation explored the effects of soybean seed hormo-priming with GA3 (50 ppm) and ET (250 ppm), either alone or in various combinations with the dietary antioxidant N-acetyl-L-cysteine (NAC; 30 mM) on germination and seedling performance.

NAC-reversible effects were observed on different soybean seed and seedling attributes following GA3 and ET hormo-priming. Early and synchronized germination (improved speed and time of germination) and improvement in post-germination growth parameters (radicle length, thickness, fresh weight, length- and weight vigor indices, and stress tolerance index) indicated positive priming effects of GA3 and ET.  Our results, therefore, could serve as a model for other agronomically important cereals, legumes and vegetable crops, for improving germination, seedling growth, establishment, and yield.
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(pp. 53-62)
Imbibition and Vigor of Chemically Scarified Poncirus trifoliata Seeds
Marcela Andrea Catraro, Damián René Poggi, Agustín Ricardo Quadrelli,
Leonardo Martín García, Norberto Francisco Gariglio and Patricia Cecilia Flores
Poncirus trifoliata is the most important rootstock in citrus production in Argentina.  The seeds exhibit slow and uneven germination due to physical dormancy associated with the presence of seed coats.  The objectives of this research were to select the most efficient chemical scarification procedures for P. trifoliata seeds, and assess the effects of such procedures on imbibition and vigor.

A first experiment was conducted to assess the efficiency of three chemical scarification methods and their effects on seed vigor. Vigor
was determined as the germination velocity index (GVI) and mean time to maximum germination (MTMG). A second experiment was conducted to assess seed vigor and the role of seed coats in imbibition, by comparing the most effective chemical scarification method identified in the first experiment to manual removal of both seed coats and no removal of seed coats.  Percentage germination, the vigor indices GVI and MTMG, and the conductivity test (CT) were determined. Scarification with sodium hypochlorite showed the best results.  The imbibition curve of seeds with both seed coats reflected an exponential weight increase, seeds with only the testa removed had a linear weight increase, whereas fresh weight of seeds with both testa and tegmen removed followed a hyperbolic change. CT indicated that chemically scarified seeds had no significant increase in conductivity compared to seeds with intact seed coats. Scarification with sodium hypochlorite was the most effective treatment for removing the testa and also improved seed vigor.
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Optimization of Waltheria indica Seed Yield Using a Visual Evaluation Scale of Seed Head Cluster Maturity
Scott B. Lukas, Joseph DeFrank and Orville C. Baldos
The determination of seed harvest timing is important to maximize seed production yields. Indeterminate flowering patterns present a challenge to optimize the harvest of mature seed, before the point of seed shattering and subsequent losses.  A visual assessment of Waltheria indica seed heads was used to separate clusters into six discrete flower cluster categories (FCCs), based on visual parameters of flowering and green and necrotic tissue. The six FCCs were analyzed for mature seed yield and moisture content. 

Results indicated that the significantly greatest seed yield was obtained from the third FCC, containing 16.40 g of mature seed per 100 g of dried flower heads.  The flower cluster moisture content for the optimal harvest of FCC 3 was 52%, and represented the first drop in moisture content that peaked at 57%.  The initial decline in moisture content after FCC 2 can be used as a tracking indicator for the initiation of mature seed formation.  Tracking moisture content and applying discrete visual flower head attributes of FCCs could enable practitioners to optimize seed yield during harvesting efforts. This method is recommended for in-field decision making to optimize seed recovery for W. indica.
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(pp. 73-79)
Lauric Acid Composition of Cocos nucifera (Coconut) Oil
Jesse James Clarke, Andrea Goldson Barnaby and Raymond Reid
Lauric acid is the major fatty acid in coconut oil, imparting characteristic properties to the oil.  The fatty acid profile of coconut oil from different geographical locations was investigated by use of gas chromatography-mass spectrometry.  The acid value, °Brix and pH were also determined.  The percentage composition of lauric acid in the majority of samples was lower than that required by international standards.  The low lauric acid content may be due to the processing of dry coconuts that had been removed from
the tree for extended periods of time.
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