Seed Quality and Storage: Definitions and Testing in Agriculture

Orthodox Seed

Can be dried to as low as 5% moisture content without damage, able to tolerate freezing temperatures, e.g., soybean, corn, wheat.

Recalcitrant Seed

Can't be dried to moisture content below 30% without injury, and unable to tolerate freezing. These seeds live for a short time, difficult to store, microbial activity due to high moisture levels causes deterioration.

PURE LIVE SEED

The portion of seed that is LIVE and capable of GERMINATION. This excludes inert matter, dormant, and hard seed, etc.

PLS%

Purity% x Germ% / 100.

Seed Quality

Combination of characteristics that define potential performance of seed lot, and determine its value.

Physical Seed Quality

Physical make up of a seed lot.

Physiological Seed Quality

Physiological state of seed that influences performance.

Genetic Seed Quality

Genetic characteristics of seed variety.

Seed Health

Presence of diseases and pests.

Germination

An indicator of the ability of the seed to emerge from the soil to produce a plant in the field under favorable conditions.

Vigor

The capacity of seed to emerge from the soil and survive under potentially stressful field conditions and to grow rapidly under a wide range of field conditions.

Cultivar

An assemblage of cultivated plants which is clearly distinguished by any characteristics and retains its distinguishing characters when reproduced.

Seed Damage

Broken, shriveled seed may not germinate, likely to be attacked by insects or micro-organisms.

Weed Seed & Inert Matter

High quality seed should be free of weed seeds, particularly noxious types, chaff, stones, dirt, and seed of other crops.

Uniform Seed Size

Mature medium and large-size seed will generally have higher germination and vigor.

Diseased Seed

Discolored or stained seed are symptoms that seed may carry micro-organisms.

Loss of Germination

The last step in a long process of deterioration; decrease in seed vigor and other physiological changes happen before loss of germination.

Yield

The amount of crop produced per unit area, influenced by genetic characteristics.

Disease / Pest Tolerance

The ability of a plant variety to resist diseases and pests.

Adaptability

The ability of a plant variety to thrive in different environmental conditions.

Value Added Aspects

Characteristics such as protein, oil contents, etc., that enhance the value of a seed variety.

Seed health testing

Can be carried out in seed laboratories.

Diseases in seed

Initially present diseases may give rise to progressive disease development in the field and reduce the commercial value of the crop.

Imported seed lots

May introduce diseases or pests into new regions (Phytosanitary Certificates).

Seed quality attributes

The most important attributes of quality are viability & vigor.

Trueness to variety

Indicates that the seeds in a bag are of the variety stated on the label.

Seed quality aspects

The presence of inert matter, seed of other crops, or weed seed; germination percentage; vigor; appearance; and freedom from disease are important aspects of seed quality.

High-quality seed lots

Should meet minimum standards for each of the characteristics of seed quality.

Role of seed quality

Plays a vital role in crop production.

Determining trueness

Usually determined by records of seed sources, lab tests, or field inspections of the plants/seeds that produce the seed.

Field inspections

Conducted by certification agencies or representatives of commercial seed companies.

Maximum seed quality

Germination and vigor are at their highest potential when the seed reaches physiological maturity.

Seed moisture at maturity

Is very high; most crops are not ready to be harvested at that time.

Harvesting seeds

Should be done as soon as the moisture content decreases to a safe level for harvest or storage.

Seed deterioration

An unavoidable process; like all living things, seeds will eventually deteriorate and die.

Irreversibility of seed deterioration

Once seed deterioration has started, it can't be reversed; low quality seed can't be turned into high quality seed.

Variability of seed deterioration

Varies among seed kinds, and even within seed lots.

Storage potential of seed

Variable; onion seed is short lived compared to watermelon seed.

Factors affecting seed quality

Rate of deterioration depends on weather environment during maturation, harvesting, conditioning, transportation, and storage practices.

Moisture content

Determines the life of a seed.

Developing stage of seeds

Moisture content of 35-80%; not harvested.

Physiologically mature seeds

Moisture content of 18-40%.

High respiration seeds

Moisture content of 13-18%; heat at 18%; increased microbial activity in seed lots.

Seeds for short-term storage

Moisture content of 10-13%; store well for 6-18 months in open storage.

Seeds for medium-term storage

Moisture content of 8-10%; 1-3 years in open storage (30-40% R.H.).

Sealed storage for vegetable seeds

Moisture content of 4-8%.

Damage due to desiccation

Occurs at moisture content of 0-4%.

Seed conditioning

Used to eliminate or reduce undesirable contaminants such as diseased and immature crop seed, weed seed, inert matter, broken or split seed, or other crop seed.

Physical differences in seed separation

Includes seed size, length, weight, width, thickness, shape, color, surface texture (smooth vs rough), and density separations.

Quality improvement of seed lot

Can be achieved through conditioning.

Seed moisture levels for storage

May be higher than for safe storage.

Storage of high oil seeds

Don't store as well as starchy seeds.

Rule of Thumb for long-term storage

50:50- 50 F and 50% RH (or the temperature in F, plus the RH should not exceed 100).

Ideal storage conditions

Store seed in a cool and dry place.

Types of seed storage

Includes field storage, bulk storage, packaged storage, distribution storage, and farm storage.

Seed deterioration timeline

Starts from physiological maturity point onward, impacting seed capability and resulting in seed death.

Purpose of seed testing

To determine seed quality, value, obtain information for labeling, make marketing decisions, and decide on storage, planting, or selling as grain.

What does seed quality refer to?

The performance of a seed lot, including trueness to variety, germination percentage, seed count, moisture, appearance, and freedom from disease.

What is trueness to variety in seeds?

It indicates that the seeds in a bag match the variety stated on the label, determined by seed source records and field inspections.

What factors are important in seed quality testing?

Presence of inert matter, seed of other crops or weed seed, germination percentage, seed count, moisture, appearance, and freedom from disease.

What moisture content is ideal for harvesting soybean seeds?

Soybean seeds are harvested at 13-14% moisture.

What moisture content is safe for long-term storage of soybean seeds?

8-10% moisture.

What is the impact of harvesting seeds at the proper moisture content?

It minimizes mechanical injury to seeds and helps maintain seed quality.

What is seed vigor?

The property that gives seed the potential for rapid and uniform emergence and development of normal seedlings under a wide range of field conditions.

What is the significance of physiological maturity in seeds?

It is the point at which seeds reach maximum dry weight and potential for maximum germination and vigor.

What factors influence seed vigor?

Maturity level at harvest, age of the seed, mechanical injuries, disease infection, storage environment, and genetic factors.

What is the purpose of seed conditioning?

To eliminate or reduce undesirable contaminants such as diseased seeds, weed seeds, inert matter, and broken seeds.

What is the standard germination test?

A test that provides reproducible results under controlled conditions to determine seed germination potential.

What are the characteristics of a good vigor test?

Inexpensive, rapid, simple to conduct, reproducible, and correlates with field performance.

How does seed vigor affect seedling development?

High vigor seeds show faster germination speed and better emergence compared to low vigor seeds under non-optimal field conditions.

What is the Cold Test in seed vigor testing?

A method where seeds are exposed to cold conditions to evaluate their vigor before being placed under favorable growth conditions.

What is the Accelerated Aging Test?

A test that subjects un-imbibed seeds to high temperature and humidity for a short period to evaluate seed storability.

What role do certification agencies play in seed quality?

They set minimum standards for purity and germination that are accepted as requirements for high-quality seed.

What happens to germination potential and vigor after physiological maturity?

They begin to deteriorate as moisture content decreases and seeds are harvested.

What is the relationship between seed vigor and field emergence?

Seeds with higher vigor tend to have better emergence rates in less than optimal field conditions.

What can cause rapid deterioration of seed quality?

Excessive damage during harvesting and conditioning, as well as adverse weather conditions during maturation.

What is the role of genetic makeup in seed vigor?

Genetic factors influence the inherent vigor of the seed, affecting its performance and viability.

What is the importance of seed moisture levels during harvesting?

Harvesting at the correct moisture level ensures seed integrity and reduces the risk of damage.

What does the term 'seed lot' refer to?

A specific batch of seeds that are evaluated for quality and performance.

Why is seed vigor testing not legally required for labeling?

While it is not mandated, many seed producers use it as a quality control measure.

How do environmental conditions during seed development affect vigor?

Conditions such as high humidity, frequent rain, and warm temperatures can adversely impact seed viability and vigor.

What is the impact of mechanical injuries on seed vigor?

Mechanical injuries during harvesting and conditioning can lead to rapid deterioration of seed quality.