Global Strategy for the Ex Situ Conservation of Potato - Global Crop ...

! Solanum tuberosum spp. tuberosum is the most common potato and breeders prefer
well-adapted germplasm or research material with interesting properties;
! the number of collecting expeditions in the centre of diversity were very limited during
the last 10 years when compared to earlier decades;
! with the exception of some genetic gaps most wild material had been collected earlier
on.
Twenty-one out of 23 potato curators indicated that their collections exhibit some gaps and
most intend to organise future collecting missions (in the centre of diversity and/or the own
country) or to introduce germplasm from other genebanks to fill these gaps.
It appeared that 30 wild species approximately are not yet represented in the collections and
may still need to be collected. In addition, for another 25 wild species, only less than three
accessions are present in the collections (see Table 3, Annex 5). Hijmans et al. (2002)
present in the “Atlas of Wild Potatoes” information on the eco-geographic distribution of wild
relatives of potato in the centre of diversity.
In line with the information provided above, the response to the question on the expected
increase of collection size over the next five years was as follows (Table 3, Annex 4):
! Same size: 6 collections
! 5-10 % increase: 12 collections
! 20 % increase: 5 collections
Several potato curators stated that whereas they plan to extend the collections with new
germplasm to fill remaining gaps they consider simultaneous rationalization of part of their
collections.
5.4.2 Regeneration
Regeneration of wild relatives of potato
To maintain accessions of wild relatives of potato, ten genebanks regenerate the accessions
as populations and produce true seed for each accession, whereas five genebanks with
relatively smaller collections maintain these wild species vegetatively by means of in vitro
conservation (Table 4.1, Annex 4). Most genebanks producing true seed base the
regeneration on 10 to 20 plants per population, three are using 20 to 30 plants and two less
than 10 plants only. The last option results in a high probability to lose genes present in the
population due to genetic drift.
The joint annual regeneration capacity of wild species maintained in the form of true seed is
approximately 1,400 accessions. In addition, 930 accessions are maintained in vitro. Based
on the provided information (data for the percentage of accessions that needs urgent
regeneration), it is estimated that conservation of 3,600 accessions of wild species
approximately out of a total of 17,000 is threatened. The number of threatened unique
accessions is probably much lower (< 2000 accessions), assuming a substantial duplication
rate between collections.
Regeneration of native cultivars
Seventeen genebanks conserve native cultivars of potato in their collections. Most of these
genebanks (12) maintain these native cultivars vegetatively (in the form of tubers in the field
or in vitro). In addition, five collections outside Latin America maintain this type of germplasm
in the form of populations. The latter method conserves the genes in the population but does
not maintain the original genotype (cultivar). A few genebanks use both methods (Table 4.2,
Annex 4).
In general, 15-30 tubers are used for field rejuvenation of tuber material mostly obtained from
10-20 plants. For in vitro conservation maintenance of 10 plantlets is the most common
practice. The annual regeneration capacity of native cultivars is c. 5000 accessions (mainly
through vegetative propagation; only 500 accessions are maintained by true seeds).
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