Seed Storage

Seed storage is to minimize the loss of viability and vigor of seeds. Many seeds lose viability within days e.g., Cocaine (Erythroxylum coca Lamk,) and cinnamon in about 30 days and some lose in years e.g., Indian lotus, in 237 years and Silk tree (Albizia julibrissin Durazz) in 147 years. The loss in vigor is directly proportional to the loss in germination.

Types of Seed Storage

1. Short-term seed storage: Seeds are to be stored for about 6 months from one harvest to the next planting season.
2. Medium-term seed storage: Seeds may also be stored for 18-36 months to insure against a crop of poor yield and low quality, fluctuations in price and market demand against shortages during an outbreak of war, and when produce could not be sold in the current year.
3. Long-term seed storage:  Long-term storage of 5 to 50 years of germplasm and breeder seeds.

Orthodox and Recalcitrant Seeds

Seeds can be divided into 2 major groups according to viability characteristics.

Orthodox group. The period of viability increases with the decrease in seed moisture. Seeds of pulses, cereals, and oilseeds belong to this group and can be kept viable for one to many years depending upon storage.

• They can be roughly further divided into good storers e.g., okra, green gram; intermediate storers e.g., cotton, sorghum, wheat, maize, and poor storers e.g., soybean, onion, etc.

Recalcitrant group. The period of viability decreases with decrease in seed moisture. Normally they have short viability periods under ambient conditions. Seeds of oak, rubber, cacao, etc. belong to this group.

Safe places for seed storage in India

Seeds of most of the species can be stored under ambient condition to meet the minimum limits of germination for seed certification for at least 18 months, if seed moisture does not exceed 10%. When legume seeds are infested with bruchids, their viability is lost within 2-4 months of storage.

Relative humidity (RH) and temperature are two most important factors influencing seed viability during storage. Therefore, if seeds are stored in places where mean RH and temperature are not very high, the loss of viability of the seeds would be very slow. RH of 70% is usually acceptable as the maximum level permissible for safe storage. Temperature of 20 o C is considered very safe for seed storage.

Place which have been listed as good maybe considered for constructing seed storehouses with minimum of insulation and no temperature control while the places which are listed moderate, proper insulation may be given.

State	Places
Andhra Pradesh	Kurnool, Anantapur, Nizamabad
Telangana	Hyderabad, Hanamkonda
Bihar	Patna, Daltongani, Ranchi, Gaya, Hazaribagh (all places are moderate)
Gujarat	Bhuj, Dahod, Ahmedabad, Baroda, Bharuch, Jamnagar, Rajkot
Haryana	Hisar, Ambala, Karnal
Karnataka	Bellary, Bijapur, Bidar
Madhya Pradesh	Indore, Bhopal, Sagar, Gwalior, Raipur, Jabalpur (all places are moderate)
Maharashtra	Sholapur, Pune, Nagpur, Amravati, Akola, Aurangabad, Parbhani, Jalgoan, Malegaon and Buldana
Punjab	Ladhiana, Patiala, Amritsar, Pathankot, Ferozpur
Rajasthan	Jaipur, Ajmer, Bikaner, Kota, Ganganagar, Jaisalmer, Sikar, Abu, Jhalawar, Udaipur
Tamil Nadu	Coonoor, Madhurai, salem, Coimbatore, Palayankottai, Vellore, Tiruchirappalli
Uttar Pradesh	Aligarh, Agra, Bareilly, Dehra Dun, Gonda, Gorakhpur, Roorkee, Varanasi (all places are moderate)
Union Territory	Delhi

Types of Seed Storage Method

1. Commercial large-scale storage: A good store should have no window and one door. The entrance should be about 1m above the ground. Godowns must be rain-proof. There should be a rat-proof lip around the building at about 1 m height extending out 20 cm.
2. Cold seed storage: The ideal conditions for commercial seed storage are 10-14 o C temperature and 40-50% RH.
   • Seed Viability of different crops
   • 1 year= Onions, Spinach
   • 2 years Corn, Peas, Beans, Okra and Peppers
   • 3 years Carrot and Broccoli
   • 4 years= Pumpkin, Squash, Watermelons, Cauliflower, Cabbage, Eggplant and Tomato
   • 5 years Cucumber, Muskmelons, Lettuce, and Beetroot
3. Cryogenic Storage: Seeds are placed into liquid nitrogen at -196 o c, long-term storage of valuable germplasm.
4. Hermetic storage: Packing seeds in an air-tight hermetic sealed container for storage and marketing. Ex: Desiccants seed storage (germplasm seed storage).

Factors Affecting Seed Viability or Seed Storage

At physiological maturity, seeds generally have maximum germination and vigour if conditions during the growth of plants are optimum. However, seeds lose viability during storage and the loss of viability is largely dependent on the following factors.

Genetic effects:

• Inheritance of seed longevity is not limited to the species level but is also effective at the cultivar level.
• Pre-harvest factors: Effect of weather: The alpha-amylase activity was found to be significantly higher in rain-affected lots. An increased amount of water-soluble sugars was found in the rain-affected seed lots, which resulted in increased leaching of sugar during the imbibition of seeds. When the seeds were stored under insect-free ambient conditions, no decline a seed germination was observed in the lots that were unaffected by rains but a significant decline in germination was observed in rain-affected lots.
• Seed structure: Husk, chaff, or both have shown an inhibitory effect on the growth of mold and an increase in the lifespan of cereal seeds during storage. Generally, small seeds escape injury, whereas large seeds are more likely to be extensively damaged. Bean, lima-bean, and soybean are examples of seeds highly susceptible to damage.

Environmental Factors:

• Seed Moisture or Relative Humidity of Atmosphere: The amount of moisture absorbed by seeds depends upon relative humidity (RH). Seeds are hygroscopic, they lose or gain moisture depending upon the RH of the atmosphere in which they are stored.
• Temperature: In general, the higher the temperature, the more rapid the seed deterioration at a given moisture level. Seed moisture and storage temperature interact in influencing the seed viability during storage. A low temperature is more effective than a higher temperature for storing seeds.
  • Mites do not survive below 5° C and insects below 15° C.
  • Most storage fungi do not grow below 0° C.
  • The effect of temperature on an organism is correlated with the amount of moisture present because a rise in temperature corresponds with a decrease in the relative amount of moisture in the atmosphere.
• Harrington thumb rules are useful for assessing the effect of moisture and temperature on seed aging.
  • For every decrease of 5° C in storage temperature, the life of the seed doubles. This rule applies between 0 C and 50° C.
  • For every decrease of 1% in seed moisture content, the life of the seed doubles. This rule applies when seed-moisture content is between 5 and 14%.
  • Good seed storage is achieved when the % of RH and storage temperature in degrees Fahrenheit add up to a hundred but the contribution from temperature should not exceed 50°F.
• Oxygen during storage: It has been observed that oxygen is generally harmful for seed storage with a seed-moisture content of about 10% but it is beneficial for storing if seed-moisture content is sufficient (more than 25%) for repair mechanism to operate.
• Microflora and Insect: Storage fungi like Aspergillus and Penicillium, These fungi may damage seeds by
  • Decrease in germinability
  • Discoloration of embryo or whole seeds
  • Production of mycotoxin
  • Heating
  • Development of mustiness and caking
  • Total decay
• Insects can be excluded from seeds by adequate packing and storage but rodents may damage seeds. Insect multiplication can be reduced or eliminated by proper drying and storage of seeds at low temperatures.
  • Insects may be controlled by creating good storage facilities and by preventing infestation by adequate use of insecticides and fumigants.

Also visit List of Seed Born Disease, Types of Seed Dormancy, Seed Pelleting

Storage of germplasm or breeder seeds:

Storage of germplasm requires special attention if it is to be stored for a longer duration. It is very important to store breeder’s materials carefully so that they show minimum loss of viability and genetic damage.

Suggest conditions for storing breeder seeds and germplasam

Duration of storage (years)	Temperature (o C)	Relative humidity (%)
5-7	15-20	45-50
20-25	2-4	40-45
50 or more	-10	40-45