Hayes and Garber - Cucurbit Breeding

250 BREEDING CROP PLANTS
radish plants were grown under cover by Riolle and self-fertilized
seed was produced in abundance. This led Riolle to suggest
that homozygous strains be first produced. These would then
furnish material for accurate inheritance studies as well as be of
much value for economic breeding purposes. On the other hand,
Stout (1920) has stated that there is considerable self-sterility in
the cultivated radish. Up to the present, mass selection has been
most frequently used as a means of breeding radishes (Tschermak,
1916).
Inheritance and Breeding.
BEETS
Both garden beets and sugar beets
belong to the species Beta vulgaris. Kajanus (1913) made a
study of the inheritance of root forms in mangels and sugar beets.
In general, the F\ roots were intermediate between the parental
forms. Sugar beet crosses in which wedge-shaped forms were
involved proved to be exceptions. Wedge-shape was completely
dominant over walnut-form and also over long, somewhat slender
roots (post-shape) .
The other beet shapes studied were oval and
round. Most of the ratios obtained in F z could be satisfactorily
explained on the basis of four factors two involving length of
root and two concerned with form.
A marked increase in the sugar content of the sugar beet
was produced by Vilmorin through the application of the progeny
test method (see page 119). There is some difference of opinion
regarding the ease of producing self-fertilized seed. Shaw (1915)
demonstrated that the sugar beet, isolated (two miles from any
other beet plants), will set some seed. To what extent selfsterility
is a factor is unknown. The production of homozygous
forms through self-fertilization would seem worth trying as a
means of obtaining homozygous material for breeding studies.
This method seems a logical procedure for all vegetables which
are naturally cross-fertilized but which also set seed freely under
conditions of self-fertilization.
Mass selection is often used in breeding beets. Only those
roots which come up to an adopted standard are stored over
winter and set out the following spring to become the seedproducing
plants. Carrots and parsnips, when bred by mass
selection, are handled in a similar manner. Although varieties
of any one of the crops, beets, carrots, or parsnips, freely intercross,
there is no crossing between the three different kinds of