| Tuber
External Growth Defects: LITTLE TUBER DISORDER
When
many tubers form off the seed piece before sprout emergence, the
disorder is called little tuber disorder. Small tubers develop at
the same time as the seed piece sprouts. This disorder will affect
plant growth and reduce yields.
Development
and Appearance
Little
tuber disorder develops in storage due to aging of seed tubers.
Upon planting little tubers are initiated directly at the eyes of
the seed piece or on very short stolons while the seed piece is
sprouting. This can also occur in storage prior to planting. Physiologically,
it is induced by a break down of apical dominance of the eyes on
the tuber and of sprouts on the stolons. The mechanism is similar
to that for tuber chaining.
Causation
This
disorder is due to physiological aging of seed tubers as a response
to high late-season storage temperature. It occurs when seed piece
temperature is greater than 68oF and is planted in soil that is
less than 50oF. Little tuber disorder can also occur when sprouted
seed tubers or pieces are placed in cold storage and then planted.
Elevated concentrations of the gases carbon dioxide (CO2) and ethylene
(C2H4), a gaseous hormone, may induce little tuber disorder as well
as be involved in tuber chaining and heat sprouting. All of these
disorders are due to changes in hormone levels.
Susceptibility
No
difference in varietal sensitivity to this has been reported although
there are varietal differences in reaching the stages of physiological
aging.
Cultural
Practices
Since
the disorder is caused by seed tuber aging in warm storages, the
key practice is storing seed potatoes at less than 40oF, but above
temperatures causing chilling or freezing damage (NPE 11-4, 1999).
Avoid long storage of seed tubers. Avoid physiologically aging seed
such as rough handling (bruising), poor ventilation or elevated
temperatures. Do not plant in cold (<50oF), dry (<60% FC)
soil.
Summary:
External Disorders |
