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

Drying facilities/methods
The protocols for the drying of seeds are not used at the Tropical Fruit Nursery as there is no
appropriate equipment. Cleaning of the seeds is carried out by Tropical Fruit Nursery workers. For
fleshy fruits such as Mangifera indica and Annona squamosa, the seeds are removed from the
mature fruits. They are then washed and cleaned before drying. Some of the seeds such as Persea
americana are dipped in fungicide (Benlate) as a seed treatment before storage. For Citrus sp., the
fruit is cut in half, the seeds are squeezed out, washed and dried before storage. Seeds such as
Averrhoa bilembi, Phyllanthus acidus, and star fruit Averrhoa carambola the seeds are first washed
in water so as to remove the mucus on the seeds, otherwise the seeds will never germinate.
The seeds are air-dried at room temperature on a table inside the nursery building. This takes 2 - 4
days for drying depending on the prevailing weather. At the Barbarons biodiversity centre there is
an oven and a desiccator with silica gel which are used for the drying of seeds. The equipment is
rarely used due to lack of trained personnel.
Measuring seed moisture status
At the Tropical Fruit Nursery seed moisture determination is not carried out since the required
equipment is not available. Seed moisture is occasionally determined at the biodiversity centre.
Seed drying is done in an oven and is measured on a wet weigh basis. There is also a desiccator
which is used for that purpose.
Storage containers
At the Tropical Fruit Nursery seeds are stored in plastic jars and plastic bags. They are then stored
in a refrigerator at a temperature of about 18°C. The relative humidity is not controlled and the
seeds can be stored up to 6 months.
Seeds are stored in plastic airtight jars, standard plastic bags and aluminium foil bags at the
biodiversity centre. The seeds are then stored in a deep freezer at temperatures ranging from 0 °C to
-20°C.
Viability monitoring (question 5.5)
Seed quality and health are assessed visually before storage at the Tropical Fruit Nursery. There is
no initial test for seed viability and it is not monitored during storage since the seeds are stored for
about 6 months only
The seeds are tested by carrying out germination tests. After the 6 month storage period, the seeds
are usually planted out for bulking up and storage. Seed germination tests are carried out at the
biodiversity centre, normally when seed shows strange physical characteristics during storage. The
tests are carried out using both the imported and the locally made germination tray, in the nursery.
Species that demonstrate low levels of viability during initial tests, if any is carried out, are citrus
root stock seeds. Species that demonstrate low levels of viability after a period of storage usually
after 6 months are Vigna unguiculata, Citrus sp., Solanum mammosum and Carica papaya.
Constraints (question 5.10)
The priority is to materialize the project entitled “Project for the Establishment of an ex-situ field
gene bank to conserve and protect PGRFA”. The PGRDS is still seeking funds for the project.
There is a need for appropriate equipment for short- and medium-term storage of PGRFA, this
would include oven, desiccator, electronic balance, appropriate bags and containers, sealer for the
bags, deep freezer, etc. for the storage of seeds.