Hayes and Garber - Cucurbit Breeding

274 BREEDING CROP PLANTS
bud sports have been found, and in some cases these have been
used as the foundation of improved races. To justify a method
of breeding founded upon their utilization, such bud sports
must occur frequently enough to pay for the trouble of making
a systematic search for them.
A review of the experimental evidence is of considerable
interest, for this is the only means we have of deciding whether
the selection of particular trees or branches for propagating purposes
is a reliable means of producing new varieties. Of the four
apple bud sports mentioned in Table LXVIII the chief changes
were in the color of the fruits. In the Isabella grape several
sports were obtained which produced black grapes of larger size
than Isabella, and which excelled in sweetness (Powell, 1898 cited
from Dorsey, 1916). Dorsey (1916) records two large-fruited
variations in the Concord grape which arose as bud sports.
Instances of bud variations in ornamental horticultural plants
are quite common. As an example of their frequency, the work
of Stout (1915) will be briefly discussed. Extensive asexual or
clonal selections were made in Coleus and numerous color changes
were isolated as well as changes in leaf shape. The same variations
were obtained through bud sports as by seed reproduction.
Some clonal lines sported much less frequently than others.
The work on citrus fruits (Shamel and others, 1918) which has
been carried on in California, has drawn the attention of many
horticulturists and plant breeders to the subject of bud sports and
their place in correct fruit-breeding methods.
Valencia oranges
were originally introduced from three sources, but all have proved
of similar type and are now called Valencia. From this variety
12 important strains originating as bud sports have been isolated.
As a rule, single off-type branches produce fruits showing characters
which are different from the fruits borne on the remainder
of the tree. Many of these sports are of highly undesirable type.
The Washington navel orange was introduced from Brazil in
1870 by the Department of Agriculture at Washington. Thirteen
distinct
strains have been isolated through bud selection.
Thompson, one of these strains, has proved a very desirable type.
Likewise, bud sports have occurred in the grapefruit which
was introduced in California from Florida in 1890. The Marsh
is the best of six strains which were obtained by selecting bud
sports. Similarly bud sports have occurred in lemon orchards.
Shamel (1919) records an occurrence of a sporting branch in a