A Wilt-Resistant Watermelon for Florida


magnification. These spores germinate and give rise to new
vegetative plants of the fungus. This fungus (and other mem-
bers of the group), however, has no chlorophyl, the green
coloring matter which enables the higher plants to elaborate
their own food out of materials obtained from the soil and air.
Consequently, its food has to be obtained either directly or in-
directly from the higher plants. Although the wilt fungus can
live an indefinite number of years on decaying plant material
in the soil, it is capable of attacking living watermelon plants;
that is, it is a parasite. (Figure 2 shows the fungus growing
out of sections of a diseased watermelon stem.) In Iowa it
has been found that the organism is capable of surviving in
the soil for 17 years after the cultivation of melons on the land
had been discontinued. Consequently, it is necessary to develop
other means of attacking the disease than by attempting to
starve it out by rotation of crops.
 The wilt fungus may be introduced into new fields in a
number of ways. Apparently, a small number of the seeds of
melons from diseased vines carry the fungus and, when planted,
such infected seed will introduce the disease into clean soil.
More common and general means by which new areas may be-
come infested are the transportation of soil and plant material
from infested fields by water, the transportation of the fungus
in soil carried on cultivating implements and on the feet of
men and other animals. It is not unusual to find wilt first


 Fig. 3.-Young watermelon plants in pots, showing damping-off form
of the wilt disease.