Volume 37, No. 2, 2016

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Download Abstracts (free download) from oral and poster presentations given at the 106th Association of Official Seed Analysts and the 93rd Society of Commercial Seed Technologists (AOSA/SCST) annual meeting held in Portland, Oregon on June 3-9, 2016.
Seed Identification from ITS DNA Sequencing
Robert Price
Forages: the Seeds of Sustainability
David B. Hannaway

(pp. 119-135)
Catalase and Peroxidase Activities and Acquisition of Desiccation Tolerance in Hybrid Maize Seed
Enayat Rezvani*, Farshid Ghaderi-Far, Aidin Hamidi and Elias Soltani
Acquisition of desiccation tolerance (ADT) is an important process that determines seed  survival. Changes in catalase activity, peroxidase activity, and starch content of hybrid maize (Zea mays) were investigated and related to ADT, under different growing conditions imposed by different sowing dates.

Germination, vigor and seedling growth parameters were analyzed at development and maturity stages, measured as days after flowering, following 5 sowing dates, and related to ADT of developing seed on the female plant. Hybrid maize seed achieved maximum seed quality (physiological maturity) before the end of seed filling (mass maturity) and black layer formation. ADT began at the preliminary stages of development, and was completed before mass maturity. Comparing this process with changes in catalase and peroxidase activities and starch content confirmed the role of catalase activity and starch content in beginning and completion of ADT. When desiccation occurred at moderate temperatures, ADT was completed faster, and seeds reached maximum germination sooner. Mean germination time indicated that seed quality deteriorated after completion of ADT. Catalase and peroxidase activities had no strong relation to air temperature changes, but were affected by developmental and completion stages of the ADT process. This research also confirmed that environmental conditions at ADT, especially temperature, played a significant role in determining seed quality.
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(pp. 135-150)
Storage Environment Effects on Soybean Seed Emergence and Estimated Cost of Production
Michael Popp*, Elijah Wolfe, Ed Gbur, John Rupe, Craig Rothrock, Kimberly Cochran and Adele Steger
Soybean seed (Glycine max) were stored under climate controlled conditions and in different environments at a commercial warehouse in 2010 and 2011.  Stored seed were tested for germination and seed vigor in 2-wk increments, and subsequently field-planted to monitor seed emergence and assess differences in producer cost to attain target plant population densities.  

This cost was expected to vary with storage environment and initial seed quality.  In the first year and earliest planting date, initial seed quality differed among seedlots of cultivars stored, and more of the higher quality seed emerged than the lower quality seed, as expected. For subsequent planting dates, emergence declined, and the associated cost of achieving a desired plant count rose.  This change was attributed to differences in RH levels in the seed bags across a range of storage periods, storage environments, initial seed quality, and planting dates.  Avoiding a rise in RH in the seed bag during storage, as observed under non-ideal storage conditions in this study, led to lower estimated cost of production. Cost of plant establishment for early vs. late planted soybean varied as much as two-fold among storage environments in 2010 and to an even greater magnitude in 2011. With target plant populations of 25 plants per m2, variation in soybean seed storage environment during the planting season plays a large role for soybean profitability.
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(pp. 151-159)
Determination of Optimal Seed Harvest Timing for Panicum torridum Based on Growing Degree Day Heat Unit Accumulation
Scott B. Lukas*, Joseph DeFrank and Orville C. Baldos
The native Hawaiian annual grass Panicum torridum Gaudich. (Torrid panicgrass) has been selected for development of seed production protocols to aid in re-vegetation efforts throughout Hawaii.  The determination of harvest timing is an important factor needed to optimize mature seed yield.  Numerous studies have detailed the difficulties associated with rapid seed shattering in grass seed production systems, as seen in P. torridum.  The utilization of heat accumulation units as growing degree days (GDD) can be used to characterize mature seed development based on thermal time, thus providing a specific quantifiable harvest time to maximize seed yields.  

The objective of this study was to optimize mature seed harvest timing of P. torridum by creating a quantifiable heat accumulative unit (GDD) indicator value.  Results indicated that maximum seed yield occurred when accumulated GDD values after anthesis initiation were 249 and 259 for August and January planting periods in Hawaii, respectively. In cases where GDD calculation is not practical, the recommended harvest time for maximum seed yield in P. torridum is 9 d after anthesis for August plantings, and 12 d for January planting, in Hawaii. This research can be utilized by restoration practitioners to maximize P. torridum seed harvesting, and the methods can be adopted for other seed production candidates.
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(pp. 161-172)
Upgrading Seed Quality of Ryegrass Using a Blowing Procedure
Gizele Gadotti, Sabry Elias* and Adriel Garay
Upgrading seed quality through removing light-weight inert matter (LWIM), immature, broken and damaged seeds is critical for good stand establishment.  In seed testing, using seed blowing procedures with appropriate air velocity can achieve quick and efficient separation of such contaminants, rather than using visual-manual separation, which is cumbersome, time consuming and with potential variability in test results among laboratories.  The objective of this research was to identify a reasonable blowing point (RBP) that separated LWIM from pure seed units (PSUs) of ryegrass, using morphological and germination assessments.

Two studies were conducted.  The first included six perennial (Lolium perenne), two annual (L. multiflorum) and two intermediate (L. x hybridum) ryegrass samples, differing in variety, production year, seed weight and LWIM content. Five grams from each sample were blown at air velocities ranging from 1.8–3.5 m s−1. Morphological assessments and germination tests were conducted on the heavy and the light portions of the blowings to identify a RBP.  The second study was conducted to
validate the selected RBP of the first study, and included 37 annual, perennial and intermediate ryegrass samples differing in variety, production year, seed weight, and LWIM content.  The same general blower was used in both studies.  An air velocity of 2.8 m s−1 was found to be the RBP to separate LWIM and underdeveloped seeds from PSUs of the three ryegrass types. Further refinement of the RBP may be needed depending on seed size, weight and the environmental conditions under which seeds were grown and developed.
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(pp. 175-183)
Delayed Nitrogen Application Influence on Production and Physiological Potential of Soybean Seeds
Larisse Pinheiro Schmid, Carla Michele da Silva, João Carlos Medeiros and Fabio Mielezrski*
Biological nitrogen fixation is responsible for most of the supply of this element to the plant.  However, the plant does suffer from reduced efficiency during the reproductive period.  The objective of this research was to study the yield and physiological quality of soybean seeds subjected to different doses of N with delayed application till the early grain filling stage.

Treatments consisted of six different rates of N application: 0, 30, 60, 90, 120 and 150 kg ha−1), using urea as the source. Productivity and thousand seed weight were the variables evaluated for yield, while physiological seed quality was evaluated by measuring germination, seedling length with the associated seedling dry matter of the aerial plant part and the root dry weight, electrical conductivity, field emergence and the associated length and dry weight of normal seedlings. No significant increase in soybean yield was observed following delayed N applications.  Physiological seed quality was affected by different N doses when evaluated using dry matter of the aerial plant part and the root dry weight, as well as electrical conductivity. Soybean production was not influenced by the addition of nitrogen fertilizer, but applying N during grain filling improved physiological seed quality, as demonstrated by some vigor tests.
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(pp. 185-194)
Color as Maturation Indicator for Maximum Seed Quality of Sterculia urens
Maitreyee Kundu* and Shilpee Singh
Determining optimum harvest and collection time before natural dispersal of seeds of many species is critical for securing better collections.  Sterculia urens seeds, a commercially important tropical deciduous tree, have a short maturation period and disperse within a very short time after full maturation.  Though seed color is the most suitable maturation indicator, not all seeds mature at once.  This study aimed to identify the optimum harvest date for seed quality by evaluating maturation indicators.  

A seed changes color during maturation from white to brown, black and then gray. Seeds were harvested at different stages of development; percentage of each color category, dry mass, moisture content, germination, desiccation tolerance and seed vigor were evaluated at each developmental stage.  At 53 days after anthesis (DAA), dry mass was highest regardless of color.  Seed moisture content declined with development for each color. Germination capacity of white and brown seeds was low compared to black and brown seeds at all maturation stages.  However, maximum desiccation tolerance was observed in seeds at 45–50% moisture content, irrespective of color and maturation stage. At 57 DAA, post-harvest drying increased germination of white and brown seeds to comparable levels as black and gray seeds, but did not improve vigor.  From 53–57 DAA, maximum seed quality was achieved by gray and black seeds, a good indicator for the best collection period.
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