Improving the identification, handling and storage of “difficult” seeds ...

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The process results in slow seed drying and takes 2 to 4 weeks to complete - resulting in the
seeds maintaining viability
Measuring Seed Moisture Content
▪ The MC of seed is routinely measured. After harvesting, before and after drying of accessions.
▪ Destructive method of MC Analysis is used. About 2.5g of seed is ground using grinder on a
small metal tray, then put on switched-on moisture analyser and then reading taken after few
minutes
▪ For germplasm conservation, the recommended MC for storing cereals is 4 – 7% and legumes 7
– 8% which is slightly higher due to their oil content
▪ Data is then entered in the Moisture Content Data File
Storage Containers
▪ SPGRC stores seeds in deep freezers, at –20 o C, in aluminium foil packets (for Duplicate
Collection) and in bottles (for Safety Duplicate Collection).
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Seed is kept under airtight conditions and frozen.
Gene bank is well ventilated. The ventilator sucks in cool dry air and pushes out warm, moist air
resulting in ideal conditions for germplasm to remain viable for a long time.
Viability Monitoring
▪ Seed viability is determined upon receipt of accessions and is monitored periodically during
storage. Germination tests are carried out to ensure if the entry is fit for storage. Seed is stored if
the viability is above 85%.
▪ Seed germination tests use distilled water, filter paper and Petri dishes, for small grains like
Sorghum bicolor (Sorghum), Pennisetum glaucum (Pearl millet). For large grains like Zea mays
(Maize), Phaseolus vulgaris (Beans), paper towels are used with distilled water.
▪ Replicates of 50 x 2 seeds are used per accession. A germinator is used to germinate accessions.
It is set in a way that it simulates growing field conditions of 100% (light), 20 o C (temperature)
and 90% (relative humidity).
▪ Viability monitoring is systematic, using a printed hard copy of accessions in the gene bank.
When an accession’s viability falls below 85%, regeneration is recommended.
▪ Accessions to be tested are withdrawn from the Gene bank and exposed for 48 hours (2 days) to
break seed dormancy, and then put in deep freezer for 48 hours (2 days) to kill fungi or bacteria.
On the 5th day, accessions are then placed in a switched-on Germinator. Germination normally
occurs after 5 – 10 days depending on the species being tested.
▪ Cross-pollination is avoided by covering plant flowers before flowering (booting stage) with
waxy pollination bags.
Species which demonstrate low viability levels during initial tests and after a period of storage
Glycine max Mucuna deeringiana Arachis hypogaea
Alium cepa Cleome gynandra Carica papaya
Challenges
▪ Need for additional freezers in the gene bank as it is received annually from NPGRC’s.
▪ Donor-dependent procurement arrangements for storage materials like aluminium foil packets,
bottles and adhesive labels, etc, which normally have to be imported from outside the SADC
region.
▪ Inadequate financial resources for regeneration, characterization and multiplication of the
existing germplasm at SPGRC and the SADC region in general.
▪ Need to disseminate and maximize information on the Use (utilization) of Plant Genetic
Resources to the end users.