Hayes and Garber - Cucurbit Breeding

POTA TO IMPRO T 'EMEN T 229
from pink to white tubers, two permanent changes from long to
round tubers, and four instances of changes from shallow to deep
eyes were observed. On the basis of the modes of inheritance of
these characters, the hypothesis was made that the changes
resulted from the loss of dominant factors. Experiments in
selection for high nitrogen content gave negative results. The
statement was made, "it is true that all of the asexual variations
have been losses of characters, while in sexual reproduction the
formation of new characters occurs. 77 This certainly substantiates
the belief that the production of improved varieties of
potatoes through bud mutation is not a promising method of
attack. East quotes A. W. Sutton, who states:
"I have no hesitation in affirming that there is no potato in commerce
in England, and I might say in Europe, which owes its origin as a distinct
potato to bud variation in any form whatever."
If this statement is true, it seems fair to conclude that there has
77
been a somewhat loose usage of the term "bud mutation in
its
application to raising the standard of a variety by any of the
well-known methods such as tuber unit or hill selection (see
Chapter XVIII). Accumulated evidence certainly points to the
belief that the chief value of such work rests on the probable
elimination of degenerate strains. Evidence from Canada
presented by Macoun (1918) is particularly illuminating. Four
varieties, Early Rose, State of Maine, Empire State, and Delaware,
were grown in Canada at the Experimental Farm at Ottawa
from 1890 to 1909 inclusive. The better tubers were selected
from each year 7 s crop and used to plant the following crop.
Results are presented in Table LVII.
TABLE LVII. AVERAGE YIELD OF POTATOES OVER THE FIRST FOUR AND
LAST FOUR YEARS OF A 16-YEAR PERIOD AND SUBSEQUENT
YEARLY YIELDS OVER A FOUR-YEAR PERIOD