Genetic resources conservation is vital to global food security and poverty alleviation. IITA’s Genetic Resources Center (GRC) plays a major role in the conservation of seed crop germplasm in order to prevent the genetic erosion of these crop species and maintain a genetic base for crop improvement.

IITA conserves a collection of seed crops that includes cowpea (Vigna unguiculata), soybean (Glycine max), maize (Zea mays), Bambara groundnut (Vigna subterranea), African yam bean (Sphenostylis stenocarpa), wild vigna (Wild Vigna species) and some miscellaneous legumes (Annex 1). The seeds are maintained at both medium and long term cold storage at a temperature of 50C and -200C, respectively.

Accessions at IITA are conserved for the purpose of research, breeding and training for food and agriculture in the framework of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA). The Genetic Resource Center’s aim is to conserve its plant genetic resources under conditions that meet and exceed recognized international standards based on current technologies and scientific knowledge.

 

The purpose of this SOP is to give detailed instructions to ensure consistency in seed conservation activities while demonstrating compliance with international genebank standards.

 

Crops Number of Accessions
Cowpea (Vigna unguiculata) 15,379
Soybean.(Glycin max) 4,841
Bambara groundnut (Vigna subterranea) 1,913
Maize(Zea mays) 1,561
Wild vigna species 1,543
African Yambean (Sphenostylis stenocarpa) 456
Total 25,693

Processes

REGENERATION

Regeneration is the renewal of germplasm accessions by sowing seeds or planting vegetative materials and harvesting the seeds or plant materials which will posses the same characteristics as the original population.
Germplasm regeneration is the most critical operation in genebank management, because it involves risks to the genetic integrity of germplasm accessions due to selection pressures, out-crossing, mechanical mixtures and other factors. The risk of genetic integrity loss is usually high when regenerating genetically heterogeneous germplasm accessions. Germplasm regeneration is also very expensive. Is usually necessitated for the following reasons

Low seed stock, Seed not previously indexed for viruses and Low viability of seed lot

Conservation

PLANTING

PRE-PLANTING OPERATIONS

Seed scarification
Scarification is necessary for the effective germination of some of the seeds, especially the wild Vigna species. Mechanical scarification is done by gently scratching the seed coat with a surgical blade or any sharp object that can open up the seed coat to allow water absorption

Seed dressing
Add 0.15g of mancozeb (a fungicide) to each paper envelop. Shake the envelop gently to allow the seed to get full coating

Making of shallow furrow of about 0.5cm deep in the soil inside the pot and sow 4 to 6 seeds in two rows per pot.

Wedding and insect control
Hand weed the pots when necessary to maintain a weed ree- environment for the plant and apply insecticides, eg Karate 5EC, ACTELLIC 25EC and CLEPEST CCVP 1000g/LEC.

Pollination
Is a process in which pollen is transferred to female reproductive organ of the seed plants, thereby enabling fertilization and reproduction through growth of the pollen tube and eventual release of sperm Both Gymnosperms and angiosperms undergo species.

Fertilizer application and staking
Apply 12g of triple super phosphate to each plot and stake each pot as soon as plants begins to climb to avoid accession interlocking during twining.

CHARACTERIZATION

Characterization is the description of plant germplasm. It determines the expression of highly heritable characters ranging from morphological or agronomical features to seed proteins or molecular markers .Characterization of germplasm is essential to provide information on the traits of accessions assuring the maximum utilization of the germplasm collection to the final users.

HARVEST

The physiological maturity of the seeds is usually determined by their dryness and brown pod color as well as by the dehiscence ability of the pods. Before the commencement of harvesting.

SEED PROCESSING

Pre-drying:
Print out the list of newly harvested accessions are match with the accessions newly brought in for pre-drying. Any mismatching accession is kept aside and investigated. Newly harvested seeds are maintained in a clean glasshouse for pre-drying until further processing but not for longer than 2 weeks. Pods and seeds remain in their harvesting bags with associated data.

Threshing and purifying:
Seeds are separated from their pods and cleaned using mechanical threshing or blowing machines

Fumigation:
Fumigate seeds in batches of 100–150 accessions using 57% aluminium phosphide fumigation tablets. The fumigation chamber is kept closed for 72 hours following treatment. Seeds are then allowed to aerate for at least 3 hours before cleaning commences.

Seed cleaning
Newly harvested accessions are transferred to GRC facilities. Seeds are separated from their pods and cleaned using mechanical threshing or blowing machines or manually (for small samples or when equipment is not available). For manual cleaning, harvesting bags containing the pods are beaten gently with a wooden stick. Each bag is emptied in an aluminium tray and seeds are separated from their pods by hand.

Purifying and identity verification
Empty each processing bag onto an aluminium tray and eliminate any debris (broken seeds, inert materials, infected seeds).

For each accession, compare seeds with their respective seed file (conformity check) Seed samples are cleaned by eliminating broken seeds, chaff, inert materials and off types.

For each accession, seeds are compared against the respective seed file (identity verification) If the seeds in the harvested sample match the seed file, the procedure continues.

If the seeds in the harvested sample do not match the seed file, the non-matching accession is set aside and compared against additional samples of the same accession, if available. Any samples that do not conform to available samples are eliminated. Seed file is used to verify the identity of the newly harvested sample. Clean seeds are returned to the processing bags with their respective tags.

Seed drying
Transfer the ranked trays to the drying room (relative humidity: 10–15%; Temperature: 16–18oC) Then arrange the seed bags serially on the dehydration shelves. Turn the seed bags upside down every 2–3 days to allow homogeneous dehydration.

Moisture content
Seed moisture content is an important factor that determines the rate at which seeds will deteriorate in gene banks and allows the prediction of the potential storage life of each seed sample. Seed moisture content may be determined with the use of a seed moisture reader or gravimetrically depending on seed quantity of each seed lot.

Once a new batch has been placed on the dehydration shelves, list of the samples is captured electronically, the moisture content is then monitored as follows using the seed moisture reader method (SINAR AGRIPRO

VIABILITY TESTING

The purpose of viability testing is to assess seed quality and seedling vigor and to predict the performance of the seed and seedlings in the field. Viability testing at the GRC is conducted using the “paper sheet” method (https://www.uaf.edu/files/ces/publications-db/catalog/anr/FGV-00249.pdf?). Germination in this procedure is defined as the emergence or development of essential plant structures from the seed embryo that would indicate normal plant development under favourable conditions in soil. Approximately 500 samples are viability tested weekly at the GRC.

CONSERVATION

In situ conservation

This type of conservation refers to the conservation of germplasm in ecosystems and natural habitats and the maintenance and recovery of viable populations of species in their natural surroundings. In the case of domesticated or cultivated species, it refers to their conservation in the surroundings where they have developed their distinctive properties. This is generally done in protected areas mostly for the conservation of wild relatives, and on-farm or in home gardens for the conservation of cultivated species. This type of conservation is not described further the Crop Genebank Knowledge Base.

Ex situ conservation

This type of conservation is the storage of seeds or plant material under artificial conditions (other than their natural environment), to efficiently and effectively guarantee its longevity viability and availability. It is the type of conservation mostly used in gene banks. It covers a range of methods suitable for various types of seeds or plant materials. It ranges from cold storage of seeds or propagules.

With ex situ conservation two types of storage are recognized: storage of samples for long-term security – referred to as base collections long-term storage and storage of samples for immediate use – referred to as active collections. medium term storage

The storage conditions and distribution arrangements of these stores vary.

SEED COUNTING AND WEIGHING

This step takes place when seeds have reached the minimal water content and the germination percentage is known. Weigh the total seed lot with an electronic balance. Sort 100 seeds with a counting machine, weigh them deduct from the total number of seeds in the seed lot.

PACKAGING

Packing and labelling materials used at GRC are impermeable to water, withstand freezing and are suitable for long-term use. Seed packaging is done in an air-conditioned room where the temperature and relative humidity is controlled to prevent the seed from re-absorbing moisture.

Seeds are packed for medium and long-term, for medium-term storage (50C) seeds are packed in an airtight plastic jar. For long-term storage (–20 0C) and safe duplication, seeds are packed under vacuum in laminated foil.

SAFETY DUPLICATION

This is the duplication of a genetically identical sub-sample of the accession to mitigate the risk of its partial or total loss caused by natural or man-made catastrophes. The safety duplicates are genetically identical to the base collection. Safety duplicates include both the duplication of material and its related information, and are deposited in a base collection at a different location, usually in another country. The location is chosen to minimize possible risks and provides the best possible storage facilities. We duplicate our accession in Svalbard (Norway) and Saskatoon (Canada).

SEED DISTRIBUTION

Germplasm distribution is the supply of representative samples of seeds or plant material accessions from a gene bank in response to requests from germplasm users. In general, seeds or plant material is only distributed from active collections.