Taxonomy - The Potato: Botany, Production and Uses - page 22

from S. stenotomum and is characterized by its lack
of tuber dormancy. After S. stenotomum originated
through selection from its wild progenitors in
the brevicaule complex, the tetraploid S. tuberosum
subsp. andigenum arose through hybridization
between S. stenotomum and another member
of the brevicaule complex, accompanied by poly-
ploidization and selection. Sukhotu and Hosaka
(2006) suggested that the initial S. tuberosum
subsp. andigenum populations arose by multiple
origin from S. stenotomum . Finally, transporting
South American tetraploid material to Europe
caused it to adapt to long-day circumstances,
producing S. tuberosum subsp. tuberosum .
Hawkes (1990) suggested that the origin of
S. tuberosum subsp. tuberosum from S. tuberosum
subsp. andigenum actually occurred twice, the
first time by transporting South American land-
races from the Bolivian Andes southward to-
wards Chile, where subsp. tuberosum still occurs
at low altitudes.
The late blight epidemic in Europe in the
1840s virtually wiped out the originally intro-
duced material and this was replaced by new
introductions. Already, the origin of the first
introductions was a matter for debate, with
Juzepczuk and Bukasov (1929) arguing that
these were subsp. tuberosum from Chile, while
most other authors assumed these to be subsp .
andigenum , probably from Colombia (Grun,
1990; Hawkes, 1990). Also, the material intro-
duced after the late blight epidemic has been
identified as either subsp. tuberosum or subsp.
andigenum . Spooner et al . (2005) looked at
nuclear and chloroplast markers of potato var-
ieties in India that presumably resembled the
original subsp . andigenum introductions, because
late blight did not arrive in India until 1870.
They found that the early introductions to India
already contained material of both subspecies.
Also, the landraces of the Canary Islands—where
the potato was first introduced—contained both
types, indicating that the introductions before
the late blight epidemic already contained ma-
terial from both the Andes and Chile (Rios et al .,
2007). Ames and Spooner (2008) studied his-
torical herbarium specimens and concluded that
although the Andean potato appeared in Europe
first, the Chilean potato was already present
long before the late blight epidemics. Also, the
Solanaceae Source website summarizes the situ-
ation as follows:

The Andean potato first appeared in Europe
around 1700 and persisted until 1892, long
after the late blight epidemics, while the Chilean
potato first appeared in Europe in 1811, fully
34 years before the late blight epidemics and
persisted until the present day, when over 99%
of extant modern potato cultivars possess
Chilean cytoplasm. These results support
original introductions from the Andes, but
refute the idea that the late blight epidemics
beginning in Europe in 1845 stimulated
introductions of Chilean germplasm as breeding
stock to combat this disease, or eliminated the
Andean potato.

( http://solanaceaesource.org/ )

Utility of polyploidy to subdivide
the crop and the use of ICBN/
ICNCP categories

Since the description of the cultivated potato as
a species, S. tuberosum , (Linnaeus, 1753), tax-
onomists dealing with the crop have added a
number of species to accommodate the various
types of cultivated material found in South
America. Some of this material arose through
hybridization between cultivated material and
wild species of different ploidy levels, leading to
diploid, triploid, tetraploid, and pentaploid culti-
vated potatoes. All of these received Linnean
taxon names, while the species S. tuberosum was
subdivided in two subspecies (subsp . tuberosum
and subsp . andigenum ), to emphasize the dis-
tinction between the “modern”, “western”,
“common” potato and the South American
landraces.
As mentioned above in the paragraph on
the history of the taxonomic classification of
the cultivated potato, Dodds, in a chapter of
Correll's 1962 treatment, proposed the ex-
tremely sensible solution to consider all the ma-
terial of the potato crop as one cultigenic spe-
cies, S. tuberosum (besides the two hybrid
species, S. × juzepczukii and S. × curtilobum ) and
to recognize five groups within this species for
the different types and ploidy levels, applying
the cultivar-group classification advocated in the
ICNCP (Brickell et al ., 2009), rather than the
formal taxa in use under the ICBN (McNeill
et al ., 2006). His approach took into account
the difference between taxa like species and
subspecies (suitable to classify populations of
wild plants) and classificatory units designed