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

Measuring seed moisture status
Using refrigeration drying, seed moisture will be reduced to between 3-7% within 30-40 days.
Moisture tests are performed on a few random samples before seeds are sealed for storage.
Destructive methods are used – oven method or infra-red.
Storage containers
High quality aluminium foil packets.
Viability monitoring (question 5.5)
Germination is tested before sealing and storage and then every 5-10 years. The NPGRC is situated
within the same building as the Official Seed Testing Station that is ISTA accredited. All
germination tests are done for the NPGRC by the Official Seed Testing Station using the ISTA
rules.
Species that exhibits initial low viability include tree species and wild species (i.e. Solanum sp. and
Aneilema sp.) of which germination protocols are unknown. Although the NPGRC has not been in
existence long enough to provide accurate examples of species losing viability over longer periods,
a general observation has been that vegetable species are more prone to losing viability.
Possible germination problems that can be encountered
Avena Dormancy may occur in freshly harvested seed. Can be broken by placing the
planted seed samples for 5 days at -2°C and thereafter at 20°C for the required
germination period.
Beta Difficulties in evaluation of seedlings infected with fungi (Phoma betae) may arise
and the following is recommended:
▪ Pre-washing, i.e. placing the seeds in running water at 25°C for 1 hour and then
drying back overnight on a piece of filter paper, to remove the inhibitory
substance.
▪ A fungicide pre-treatment may be applied before planting the seeds to reduce
the occurrence of the spread of fungi on the substrate.
▪ Use a substrate that offers a barrier between seeds to also limit the spread of
infection from one seed to the other.
Brassica Seedlings should not be evaluated before all essential parts have developed i.e. the
cotyledons have freed themselves form the seed coat. The evaluation of the
cotyledons is very important to determine necrotic and decayed areas and also for
chlorophyll deficiency i.e. white or yellow areas). Seedlings must therefore be
grown in full light or at least 24 hours before evaluation takes place.
Helianthus A well developed primary root is essential when evaluating sunflower seedlings as
this root will need to anchor the plant. The development of the primary root tends
to be better in the between paper (paper rolls) than the sand substrate.
Oryza Germination can be promoted by pre-soaking the seed for 48 hours in water.
Thereafter the seed is planted in the normal manner. The sand substrate can be
used for rice.
Phaseolus Bean seed can be planted using the between paper or sand method. Depending on
the method chosen the seedlings may look very different. The sand method is
recommended allowing the seedlings to develop to the stage where the primary
leaves expand and show photosynthesis activity.
▪ Primary leaves are considered normal if they show the normal shape and are
not smaller than ¼ of the average leaf size in the sample.
▪ Primary leaves that are damaged or deformed must have 50% of the original
leaf area functioning normally.
Zea Coleoptile defects, i.e. split, bent over, to missing, split at the base and split at the