Redefining Seed Quality
by Erica Renaud

As an organic seed company specializing in open-pollinated varieties, we are often asked by our customers how we ensure genetically pure, high-germinating, viable seed year-in and year-out. We have all experienced at one time or another the pure excitement of seeding in late winter, to find no seedlings. Or, in the excitement of one's spring planting, to find that your purple-podded bean is actually green or your red radish, is well... see the middle row in the photo below.

The definition of seed quality is broad, incorporating several parameters, including genetic quality, physical quality, and seed health. Quality is assured through both proactive and retroactive methods. These include preventive maintenance, such as growing and evaluating every seed lot, as well as continually selecting for trueness to type, active quality programming from field to pack, third-party quality verification, customer quality input, and retroactive quality feedback to our seed producers. Through this multi-pronged approach, Seeds of Change ensures that only the highest quality organic seed is offered.

Seed quality parameters provide valuable information on the suitability of seed for planting, particularly their potential for germination, the promptness of their emergence from the soil, their ability to establish uniform, vigorous seedlings, and their production of healthy crops with good yields. Therefore, in the seed industry, quality serves as the basis for price differentials, facilitates the diagnosis of seed related problems and their probable causes, and provides seed producers with a decision tool for their various operations, including storage and marketing.

The concept of seed quality, as it relates to organic seed, is in its infancy and is actively being researched. Efficacious substitutes for the often toxic chemical inputs of conventional seed crop production and improved agronomic practices to improve seed yield are still being identified, but have come a long way as the organic seed industry has developed over the last two decades.

In the terminology of the industry, seed quality is measured by "seed quality attributes" while the factors that affect these attributes, either positively or negatively, are referred to as "seed quality determinants." These determinants and attributes interact with one another to determine the quality outcome of the seed.

What are Seed Quality Attributes?

	Micaela Colley and grower Randy Carey assess field quality.
	Steve Peters inspects the progress of tomatoes growing in an isolation tent.
	Erica Renaud gathers data on carrot seed grown in the pollination tent.

Genetic quality: often referred to as "trueness to type," cultivar purity or varietal purity. The strict control of seed generations, coupled with the careful monitoring of seed production at every stage, provides ways of ensuring the authenticity of a seed lot.

Physical purity: the range of components included in a seed lot. These include the seed of the stated species (i.e. pure seed), seed of other species (i.e. other crop species and/or weeds), and contaminants which may include materials from seeds, parts of plants, living organisms (not of plant origin) and soil particles. The Seed Cleaning & Quality Coordinator, Emily Skelton evaluates each individual lot of seeds for any of the above impurities upon its arrival on site, using a color sorter to remove any incorrect plant species or inert material of another color from the lots. Seeds of Change is developing seed specifications for its grower network that outline purity expectations. (See Steve Peters' article on weed contamination in this issue of the eNewsletter for further information on this topic.)

Seed health: defines the extent to which seed-borne pathogens and/or pests are present. Seeds of Change works collaboratively with the USDA Salinas Experimental Station to determine prevention, testing and treatments for seed-borne diseases. Lots are also tested for seed-borne diseases by a third-party certified laboratory.

Seed viability: refers to the potential germination and subsequent production of a seedling of the stated cultivar. Although the viability of an individual seed can be determined it is more usual to refer to the germination potential of a seed lot. In this context a seed lot is selected from a specific population and evaluated for germination.

Seed vigor: is defined by ISTA (International Seed Trade Association) as "the sum total of those properties of the seed which determine the level of activity and performance of the seed or seed lot during germination and seedling emergence." All Seeds of Change seed lots are not only tested by a third-party certified lab for germination, purity and pathology, but Seeds of Change's Greenhouse Manager, Emily Gatch tests every seed lot on our own Research Farm under applied conditions for germination rates, percentages, and seedling vigor. We then compare our results to the laboratory conditions and work together to determine best propagation and testing methods.

Moisture content: the percentage moisture of the seed lot. It is a factor in the longevity of the seed in storage. Seeds of Change checks each seed lot for moisture content and stores all seed in carefully climate-controlled conditions.

GMO testing: By law organic seed can not contain genetically modified organisms (GMOs). Where appropriate, such as with all corn varieties, Seeds of Change has every new lot of seed tested for GMO contamination by a third party.

What are Seed Quality Determinants?

Original seed source: impacts the purity of a seed lot, the incidence of noxious weed seed, the varietal purity of the crop, the incidence of seed-borne diseases, the effectiveness of seed treatment, and seed vigor.

Seed production method: Different crops require different isolation distances depending on their reproductive method.

Seed harvesting: should be completed as soon as the moisture content decreases to an appropriate level. Although germination potential and vigor are at their highest when the seed reaches physiological maturity, the moisture level present at that point makes it impractical to harvest and process the seed. After maturity, germination potential and vigor begin to deteriorate, thus making the timeliness of harvest fundamental to the quality of seed.

Field contamination: includes biotic and abiotic agents. These contaminants could come from the original seed sown, volunteer plants of other previously grown crops, pesticide residue in the soil, disease innoculums in the field, and weed seed present in the land being used for cultivation. Therefore, the history of the land to be used, including the crop history, is very important in taking actions to avoid or limit contamination.

Seed storage: conditions can also greatly affect deterioration rates. It is important that seeds be stored under conditions of low humidity and low temperatures to ensure seed viability. Seeds of Change is located in an area that has extremely low humidity, which is beneficial to preserving seed viability. Also, Seeds of Change has a temperature and humidity controlled facility where all seed is stored in muslin bags.

Conditioning: refers to the techniques used to remove dead seed, off-colors, seed chaff, and broken seed from a seed lot. At the Seeds of Change Research Farm we have a state-of-the-art facility to mechanically clean seed lots.

Applied Approaches to Attain Quality:

Identifying the best available germplasm
Once the decision has been made to develop a certain variety or crop category, it is necessary to assess the current availability, intrinsic value, and desirable traits of available crop germplasm, as well as the time and resources necessary to develop a quality seedlot through breeding, selection, and production.

	Harvest data is gathered on the NM Research Farm.
	Emily Skelton explains the Seeds of Change seed cleaning equipment to a farm tour group.
	John Martinez tracks seed in the Santa Fe cold storage facility.

Quality checks
Seeds of Change performs annual field trials of all of our varieties in multiple locations. All lots contracted each year are trialed on the Seeds of Change Research Farm. Any lots that will be included in the bulk catalog are also grown in field-scale trials on farms in various parts of the country and are often evaluated for quality or vigor against "competitors" lots or possible new germplasm to compare performance and make decisions about appropriateness for our market(s).

Cultivar trials
As a prelude to a specific breeding program, all available material is evaluated. Varieties are screened to identify those suitable for a particular climate or a particular season. For example, lettuces are screened to identify mid-season performers for year-round lettuce production. Cultivar trials assist farmers and growers to select those cultivars that are suitable for particular production systems, maturity periods, and market outlets.

Stock seed development
Stock seed refers to the carefully selected and maintained seedlot from which subsequent lots of seed are grown for sale to our customers. This seed may come from existing cultivars or germplasm that require minimal selection to reach the stock seed development stage or may involve years of extensive breeding and selection. Through the use of Quality Assurance (QA) trials, our cultivars are compared to the same or comparable cultivars from other sources. Enough individuals of each entry are produced to use plants of a designated strain for stock seed production if a superior strain is identified. If the source of the cultivar or germplasm is variable but holds potential as a "finished variety" with selection alone ("revitalization"), then larger numbers of each trial entry are grown out to assure "room to select." This selected stock is then put through QA again to see if it requires more selection or is uniform enough to be deemed stockseed.

Research & development
If no current cultivars or germplasm exists for a desired variety, we must then decide the level of R&D that would be required to develop the variety from existing seed stocks. Key components of this process are understanding the breeding timeframe and resource allocation necessary to develop a quality variety and the needs for the variety in the marketplace.

Conclusion
In order to ensure that organic seed is of the highest possible quality, agronomic practices and pest control procedures appropriate for the organic seed crop production systems must be developed and adopted. These practices should ensure that the genetic, physical, and physiological integrity of the seed crop is maintained during the process of reproduction. These actions relate to, amongst other things, the choice of production inputs including careful selection of the plot of land to be used for organic crop production (for cleanliness from disease agents, fertility, and absence of chemical residue carried over from previous crops) and appropriate procedures for handling the seed crop at the production and harvesting phases—all of which could be checked through seed quality control procedures called "field quality control." When the crop is harvested it is subjected to laboratory quality control to determine seed moisture content, purity (physical and varietal), viability, vigor, weed content, freedom from noxious weed seed, and absence of chemical residues. The sum total of the results obtained from both the field and laboratory controls are used to certify the seed for sale to the grower, and to assure the best possible results in the field.

Erica Renaud
Research & Farm Manager

References

George, Raymond A.T. 2002. Vegetable Seed Production. 2nd ed. New York, NY: CABI Publishing.

Freeman, Orville L., and Alfred Stefferud, eds. 1961. Seeds. The Yearbook of Agriculture 1961. Washington, D.C.: United States Government Printing Office.

International Federation of Organic Agriculture Movements (IFOAM). 2004. Proceedings of the First World Conference on Organic Seed: Challenges and Opportunities for Organic Agriculture and the Seed Industry. FAO Headquarters, Rome, Italy: IFOAM.

Photo caption: (top) Three different radish lots demonstrate seed quality issues in the mixed colors of the middle lot.