Hayes and Garber - Cucurbit Breeding

fendleri,
POTATO IMPROVEMENT 223
which grows at a high altitude and endures extremes
of climate, with a domestic variety. The wild form produces
small tubers. In the F 2 generation forms appeared which were
identical with the wild parent together with many intermediate
types.
Most of the observed variations in
cultivated varieties have
occurred in the tubers, although the English ash-leaf varieties
are examples of a variation in leaf shape (East, 19076).
Production of New Forms. For the purpose of differentiating
between two important phases of potato improvement, Stuart
(1915) has referred to " selection" as the " isolation and asexual
propagation of desirable strains or types" while " breeding"
is used only for sexual reproduction. With certain crops, such
as the potato, this terminology is distinctive. Such a restricted
usage of the word "selection" seems undesirable from the plantbreeding
standpoint. The same idea can be obtained by the use
of "clonal selection" to refer to the asexual propagation of desirable
strains or types.
Systematic plant breeding with the idea of combining the
desirable characteristics of two parental varieties can be carried
out only after the breeder has familiarized himself with the
characters of particular varieties and of their wild relatives.
Thus, with the potato as with other crops the breeder should
first determine the ideal toward which he will work. Parental
varieties should than be selected because of some desirable
characters. By recombination of the favorable characters of
both parents, improvement may be obtained.
Gilbert (1917) has
listed certain characters of the potato which are universally desired.
Some of these are:
1. High yield.
2. Good quality.
3. Disease-resisting capabilities.
4. Good keeping quality.
5. Good color of flesh and skin.
6. Skin of desirable texture.
7. Tubers of good shape.
8. Shallow eyes relatively few in number.
9. Upright, vigorous plants.
10. No tendency to make second growth.
The desirability of most of these characters is self-evident.
The chief difficulties in the way of developing a standardized
method of attack arise from: