Hayes and Garber - Cucurbit Breeding

practical
POTATO IMPROVEMENT 233
breeder to discard "clonal selection"
as one means of
obtaining high yields, for it is a recognized fact that seed plot
methods are of much practical importance. The results, however,
are probably not due to the isolation of bud mutations but
rather to the use of tubers which have developed normally and
which furnish the right conditions to give the resultant plants
a favorable start. May not the conditions be much the same
as with any vegetatively propagated plant. Bonnier, for
example, found that about three years are required before a low-
FIG. 58. Tubers produced under such a cheesecloth cover have given good
yields during the seasons 1918 and 1919 while tubers from uncovered vines
produced very inferior yields. University Farm, St. Paul, Minnesota. (Courtesy
of Krantz.)
land dandelion transported to alpine conditions fully expresses
the characters of a dandelion plant which had been grown under
these conditions for many years. On returning the same plant
to the lowlands about the same number of years elapsed before
the plant had again fully attained the lowland habit. This is
probably not a germinal change but the normal expression of the
plant under a particular environment. With the clonally
propagated potato there is a cumulative response to unfavorable
conditions. Such conditions modify the plant's development
and therefore influence the development of the following year's
crop. There seems no reason for believing that an actual germinal
mutation has occurred.