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

A total of 346 species from the combined list are held at the Millennium Seed Bank (MSB),
representing 220 genera and 67 families. This amounts to 2067 accessions originating from 94
different countries. Table 3 shows the families represented in the combined species list with the
greatest number of accessions at MSB.
Table 3. Families represented in the combined species
list with the most accessions at MSB
Family
Accessions
GRAMINEAE 537
LEGUMINOSAE-MIMOSOIDEAE 161
LEGUMINOSAE-PAPILIONOIDEAE 607
Analysis
The species list was analysed against Kew’s Seed Information Database (Flynn et al, 2006) and the
MSB’s in-house Seed Bank Database, in order to produce information on seed storage behaviour
and germination requirements. It was also cross-checked against a recent study of species seed
longevity characteristics (Walters et al, 2005)
Storage behaviour
420 individual records of storage conditions were found in SID, representing 375 species from the
combined species list. Most of the species showed orthodox storage behaviour (Table 4). Orthodox
seeds can be dried to low moisture contents and their longevity increases with reductions in
moisture content and temperature, over a range of storage environments. Approximately 15% of
the species were “questionably” orthodox and only 5% were found to be recalcitrant. Recalcitrant
seeds do not survive drying and so are not suitable for long term storage. In SID, this category
includes seeds described as viviparous, including some aquatic species.
Table 4. Species from combined list with storage behaviour records in SID
Storage behaviour Number of species %
Orthodox 299 79.73
Recalcitrant 15 4.00
Recalcitrant? 2 0.53
Intermediate 2 0.53
Intermediate? 1 0.27
Orthodox? 21 5.60
Orthodox p 33 8.80
Uncertain 2 0.53
Total no of species 375
Of the species in the ITPGRFA list with storage behaviour records in SID, only two (Artocarpus
altilis and Cocos sp.) are recalcitrant. One (Colcasia esculenta) is classed as possibly orthodox and
the remainder are fully orthodox.
Identifying “difficult” species from MSB germination tests
The combined species list was analysed for germination data in MSB’s Seed Bank Database.
Germination testing at the MSB involves initial testing after at least 1 week of cold storage,
followed by re-testing at 10-year intervals. Initial tests are conducted (depending on the size of the
collection) until a germination percentage of 75% or more is achieved. Germination test results are
available for a total of 292 species (1620 accessions) from the combined species list, amounting to a
total of 4441 germination tests, including initial tests and re-tests (Table 5).