Storage of Seeds
Storage of Seeds: A Standard Protocol
It’s really important and essential to maintain the seed in good physical and psychological conditions from the time it has been harvested until the time they are being planted. Also, storage of seed is necessary to protect them from pest, disease and to converse them until they germinate for subsequent crop production.
Before storing a seed, the variety of seeds should be well understood. Seeds are generally categorized into the following types:
Orthodox: Seeds that can be dried without damage maintaining low moisture contents and it should be much lower than those they would normally achieve in nature. Their longevity increases with reductions in both moisture content and temperature over a wide range of storage environments.
Recalcitrant: Seeds that do not survive drying to any large degree, and are thus not amenable for long term storage.
Intermediate: Seeds that are more tolerant of desiccation than recalcitrant, though that tolerance is much more limited in comparison to orthodox seeds, and they generally lose viability more rapidly at low temperature.
A general seed storing protocol is as followed,
1. Firstly, it is to determine whether the seeds chosen are eligible for storing or not. (As all seeds are not stored successfully)
2. Healthy and ripen seeds are collected.
3. The seeds are separated and cleaned properly and carefully without damaging.
4 (a) The seeds are dried to the correct moisture level for storage and (b) in between, some of the seeds are germinated to ensure that they are in good state.
5. The seeds are packed for storage.
6. Store the seeds.
7. If the seeds stored for a long time, then germinate a sample from time to time to make sure that they are still in good conditions.
8. Prepare the seeds for sowing: Seeds stored very dry need preparation before sowing.
9. Sow the seeds.
The elaborate seed storage for Cucurbits are described below:
• The seeds of pumpkins or some melons which form in the hollow cavity of the fruit require separating from the placental tissue, washing and drying. Embedded seeds of watermelon, cucumber, melon, wax melon and squash can be removed by chopping the fruits.
• When water is added to the mixture, seeds will sink and the flesh debris, which floats, can be poured off. Fermentation helps with removing the persistent placental material encasing cucumber and bitter melon seeds. The water and seed mixture is left for 1-2 days at a temperature of 20-35°C. When seeds settle to the bottom of the container and the placental material floats, the fermentation is complete.
• Then the seeds are rinsed and left to dry. Hydrochloric acid or ammonia solution can be used for more effective cucumber seed cleaning.
• By adding some enzyme (e.g. Rapidase®️ Smart) it is possible to stimulate tissue fermentation. Some 30 minutes of vigorous stirring will free the seeds of flesh. Before drying seeds require thorough rinsing.
• Mechanical seed cleaning is not recommended for bitter melon seeds or necked seeds of Cucurbitapepo which are fragile and can easily get broken.
• Seeds of loofah and bottle gourd, which are extracted from dry fruits, require little or no processing before storage.
• However, mature seeds of most cucurbits have adherent, wet flesh which has to be removed. Seeds should be dried as quickly as possible.
• Cucurbit seeds are typically spread out to dry under warm (less than 35°C), arid conditions.
• Drying at higher temperatures or in full sunshine will reduce the storability.
• After the first drying, the seeds can be packed in paper bags for further drying with silica gel or in an air-conditioned room with controlled air humidity and temperature.
• The storage conditions for dry seeds (5-6% moisture content) involve airtight containers kept in the dark at about 5°C and 25 RH. Silica gel can be added to adsorb moisture.
• Under such conditions cucurbit seeds can remain viable for at least 10 years.
• Frozen seeds (first dried down to safe moisture content) will keep their germ inability longer.
Dr. Atreyee Kundu,
Professor, Department of Microbiology,
Techno India University, West Bengal.
Senior Research Fellow, Presidency University(Ex)