Flow Chart for Seed Germplasm Conservation
I. Drying of germplasm
For long term conservation, seeds of each accession should be dried to a moisture content of 3-7%, depending on the species. At this moisture level, the seed tissues will contain only the tightly bound water molecules which do not contribute significantly to the ageing
Seed drying upto 3-7% moisture content *
Assessment of seed viability through germination test
Samples with more than 85% germination** are allotted IC numbers by AKMU
Samples are packed in labeled tri-layered aluminium pouches, vacuum sealed and stored in LTS
Page | 171 metabolism. For attaining the recommended moisture level, the seeds are dried at 15oC temperature and 15% relative humidity in standard walk-in or batch dryers. The duration of drying will vary with the species. Oil seeds dry rapidly and attain 3% moisture content within 7 days, whereas maize seeds require more than 20 days to dry upto 7% moisture content.
Seed Moisture Testing
After the anticipated drying duration, the samples are subjected to moisture testing using the crop-specific procedure, as recommended by the International Seed Testing Association (ISTA). As per ISTA rules, the only acceptable method for seed moisture testing is the Constant Temperature Oven Drying method. However, for preliminary screening, curators can use a well calibrated digital moisture meter. For the final moisture determination, ISTA protocol involving oven drying should be strictly adhered to.
Pre-drying
If in the initial screening, the seed samples are suspected to contain above 17% (10% for soya bean and 13% for rice), a pre-drying should be conducted before going ahead with the oven- drying.
If pre-drying is required, the following procedure should be adopted:
1. Weigh approximately 4–5 g of seeds in two replicates (taken in containers of known weight).
2. Pre-dry the samples by leaving it open overnight in a warm, dry place.
3. Weigh them again (along with their containers) and determine the loss of weight (loss of moisture) by subtraction.
4. Calculate the moisture content on a fresh-weight basis.
The percentage of moisture content on weight basis may be calculated by using the formula as mentioned in the Work sheet
After completing pre-drying, further moisture testing should be done for these samples using Oven-drying method. If moisture content of the received sample is apparently below 17%, the accessions may be directly subjected to oven drying.
Materials required for oven drying a) Grinding mill
b) Constant temperature oven
c) Moisture bottles made of glass or non-corrosive metal d) Desiccator and silica gel
e) Analytical balance f) Seed material
Page | 172 Procedure
The constant temperature oven method is the standard protocol for seed moisture testing in genebanks. Prior to drying, grinding is obligatory for large seeds, seeds with seed coats that impede water loss from the seeds and oily seeds (Table 1). The samples are always tested in two replicates. There are two methods of oven drying-
Low constant temperature oven method: This method is generally used for moisture estimation of oily seeds (Table 2). The seeds in moisture bottles with their lid open are placed in an oven maintaining a temperature of 103±20C for 17±1 hours. The lids and bottles should be properly labeled. After the recommended duration, replace the lids within the oven itself and shift the bottles to a desiccator containing silica gel, for cooling. The seeds in the bottles are then weighed, along with the lid.
High constant temperature oven method: This method is generally recommended for the seeds of field crops (Table 3). The procedure is same as above except that the seeds are placed in the oven at 130±20C for 2-4 hours.
Calculation of results: Calculation of seed moisture content is done using Eqn 1. All the weights should be taken in grams upto three decimal places and the result should be reported to the nearest 0.1%.
If the seeds required pre-drying, the moisture content is calculated twice i.e once after pre- drying and secondly, using oven method. If S1 is the percentage moisture lost in the pre- drying, and S2 is the percentage moisture lost in the second stage, then the original moisture content of the sample calculated as a percentage is:
(S1 + S2) – S1 × S2 100 Table 1: Species for which grinding is obligatory
Arachis hypogaea Oryza sativa
Avena spp. Phaseolus spp.
Cicer arietinum Pisum sativum
Citrullus lanatus Quercus spp.
Fagopyrum esculentum Ricinus communis
Fagus spp. Secale cereale
Glycine max Sorghum spp.
Gossypium spp. Triticum spp.
Hordeum vulgare Vicia spp.
Lathyrus spp. Zea mays
Lupinus spp.
Page | 173 Table 2: Species for which the low constant temperature oven method shall be used
Allium spp. Raphanus sativus
Arachis hypogaea Ricinus communis
Brassica spp. Sesamum indicum
Camelina sativa Sesamum orientale
Capsicum spp. Sinapsis spp.
Glycine max Solanum melongena
Gossypium spp.
Linum usitatissimum
Table 3. Species for which the high constant temperature oven method shall be used
Agrostis spp. Lactuca sativa
Alopecurus pratensis Lathyrus spp.
Anethum graveolens Lotus spp.
Anthoxanhum odoratum Lupinus spp.
Anthriscus spp. Lycopersicon lycopersicum
Apium graveolens Medicago spp.
Arrhenatherum spp. Nicotiana tabacum
Asparagus officinalis Oryza sativa
Avena spp. Panicum spp.
Beta vulgaris Papaver somniferum
Bromus spp. Phalaris spp.
Cannabis sativa Carum carvi
Phaseolus spp.
Chloris gayana Pisum sativum
Cicer arietinum Poa spp.
Secale cereale
Citrullus lanatus (C. vulgaris) Sorghum spp.
Cucuburbita spp. Trifolium spp.
Cuminium cyminium Triticum spp.
Cynodon dactylon Vicia spp.
Cynosurus cristatus Zea mays
Dactylis glomerate Daucus carota
Fagopyrum esculentum Hordeum vulgare
When the seeds are found to have attained moisture content of less than 7%, the accessions are tested for their seed viability.
Page | 174 Recording and Calculation of Seed Moisture Content
Accession no.
Replicate/
Moisture Bottle no.
Wt of empty Moisture
Bottle with lid (g)
Wt of Moisture
Bottle with lid + seed
before drying (g)
Wt of Moisture
Bottle with lid + seed after drying (g)
Moisture content % (wb)
W1 W2 W3 (W2-W3)/
(W2-W1) × 100
Average (R I + R II)/2
R I
R II
R I
R II
R I
R II
R I
R II
Example:
Calculation:
Rep 1: % Moisture content = (W2-W3)/(W2-W1) × 100 Rep 2: Moisture content =(W2-W3)/(W2-W1) × 100
Moisture content (fresh-weight basis) = (%MC Rep.1+ %MC Rep.2 )/2