Seed Processing

For materials showing large morphological variation (genetically heterogeneous accessions), an accession should consist of at least 4000 seeds, but 12 000 seeds are ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

preferred. In genebanks, it is easier to work in weights, but seed number can easily be converted from weights if the 100-seed or 1000-seed weight is known. For example, to determine the number of seeds in a sample for which the 100-seed weight is known: Number of seeds in the sample = Sample weight (g) x 100 Weight of 100 seeds (g) Laminated aluminium foil packets are the most commonly used containers in genebanks as they occupy little space and it is easy to reseal them. Aluminium foil packets to be used in genebanks should have the following specifications: • an outer layer of 17 g m-2 Melinex, 4 g m-2 lacquer; • a middle layer 33 g m-2 (12 µm) aluminium foil, 4 g m-2 lacquer; and • an inner layer of 63 g m-2 polyethylene. 89 Manual of Seed Handling How should seeds be packaged? Packaging is best carried out in an air-conditioned room where the RH is ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

controlled. It is important to ensure that seeds taken from the drying room are exposed to ambient air for the shortest time possible so that they do not re-absorb water. 1. Decide on the most suitable container for storing the seeds. Different types of containers can be used depending on the size and shape of the seeds, and the purpose of conservation (whether for base or active collections—see section 6.2). 2. Prepare and label the containers for each accession; computergenerated self-adhesive labels and barcodes11 are now being used in many genebanks. Bar-coding ensures that information is accurate and that no mistakes occur during transcription. Prepare a label to include with the seeds inside the container. Labels should contain the following information: • Accession number • Genus and species • Container number • Weight of seeds • Date of storage 3. Weigh out ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

each empty labelled container. 4. Fill the containers with the seeds and weigh again. Calculate the actual weight of the seeds. 5. Add the label and seal the container immediately to protect the seeds from high ambient RH. 6. Check the quality of each container after sealing it by making a visual examination to ensure that there is no leakage. 7. Any container found to be below standard should be replaced immediately. 8. Move the containers into the storage room. 11 Bar-coding is a computerized coding system that uses a printed pattern of bars of varying widths to uniquely identify accessions. Bar-codes are read by optically scanning the printed pattern and using a computer program to decode the pattern. The data contained in a bar-code can vary: in its simplest form, it can ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

be just an accession number, while in other cases, the bar-code can hold more elaborate passport and inventory details. Bar-coding provides enormous benefits to genebanks by allowing data capture that is faster and more accurate to minimize errors and facilitate inventory management. Example: Sample weight = 275 g Weight of 100 seeds = 12.5 g Total number of seeds in the sample = 275 x 100 = 2200 12.5 90 Handbooks for Genebanks No. 8 9. Enter relevant data about each accession into the data file. A model for recording container and seed weight is shown in Table 6.1. Reference samples (seed herbaria) Seed herbaria are useful to check physical attributes of seeds without having to open sealed containers. Pack a small sample (five to ten seeds or pods of legumes, or 5 g of cereals) of the original seeds separately in a transparent re-sealable plastic envelope or glass vial to verify genetic ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

integrity after regeneration and during seed transfer. The samples can be stored in a cabinet with closely spaced shelves. Ensure that seeds of the original sample are never completely exhausted so that they may serve as a reference for identification.