Hayes and Garber - Cucurbit Breeding

FLAX AND TOBACCO 157
white flax and the common varieties have the same factors
These results were explained by supposing that the smallpetalled
for breadth of petal, C, one of the color factors, when alone
or in the presence
of A is an inhibition factor for flower size.
J5, when present, prevents the action of C.
Wilt Resistance in Flax. When flax is grown for several
years on the same soil, a heavy infection of Fusarium lini often
results, and complete crop failure may occur. Bolley, as early as
1901, pointed out the true nature of the disease and devised
FIG. 35. Selected and non-selected flax on wilt sick soil. Right foreground,
non-selected flax killed by wilt; left foreground, selected flax; left background,
non-selected; right background, selected. University Farm, St. Paul, Minn.,
1918. (After Stakman, et al, 1919.)
methods for its control. Seed treament and crop rotation were
shown to be beneficial as aids in the control of wilt. Seed
selection, however, proved the most efficient control measure.
In general, Bolley (1903, 1909) found that two or three years'
selection under disease conditions were necessary in order to
isolate a resistant variety. Both individual and mass selection
methods were used. Similar studies carried on at the Minnesota
Station (Stakman, et al, 1919) have confirmed Bolley
'a results.
One of the peculiar results of this work is the discovery that
resistant varieties lose their resistance after they have been