Hayes and Garber - Cucurbit Breeding

POTATO IMPROVEMENT 221
colony to England, including Thomas Herriott. Probably potatoes
were part of the stores obtained in the West Indies by Drake
and these Herriott introduced into Ireland about 1586. This was
the second introduction into Europe, the Spaniards deserving
the credit for the first introduction. It is not known from what
source the English colonists of Virginia and Carolina first obtained
the potato, but it is generally believed to have been from Spanish
or other travelers. Gerard described and illustrated the potato
in his "Herbal" in 1597. The variety he described possessed
light brown to yellowish tubers and violet to almost white
flowers.
Inheritance. 1
The transmission of potato characters through
the seed is in conformity with Mendelian principles.
Vegetative
propagation allows the breeder to perpetuate any desirable genotype
even though heterozygous, which is the usual condition in
the potato plant. While, in general, self-fertilization of a commercial
variety gives rise to seedlings which vary a great deal,
it is
comparatively easy to obtain homozygosity for some
characters.
Tuber shape and size are important characters which are used
as one means of varietal classification. Tuber shape has been
found to depend essentially on the presence or absence of a single
factor for length.
homozygous long, homozygous round, or heterozygous long.
Heterozygous long is the most variable of the three conditions.
In one experiment two varieties with round tubers when selfed
According to this hypothesis a tuber may be
produced nothing but round tubers, while twelve varieties with
oval tubers, when selfed, produced long, oval, and round tubered
progeny. Nilsson (1912-13) found one variety of potato that did
not breed true for round tubers. Long tubers were dominant to
round in Fruwirth's (1912) experiments.
Depth of eye is a character of considerable economic importance.
In general, shallow eyes were found to be dominant over
deep eyes.
Several factors, in addition to a chromogen body, have been
recognized in tuber coloration. Red potatoes contain two genes,
R, a reddening factor, and D, a developer of pigment. Purple
and black tubers have, in addition to R and D, another factor,
1 The following discussion is based on inheritance studies made by
SALAMAN (1909-11, 1910-11, 1911, 1912-13) and EAST (19106) except
where otherwise noted.