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Tuber
Internal Growth Defects: HEAT SPROUTING
Hair
or spindle sprouting may occur in the field or in storage. It is
associated with hot and dry conditions during late tuber growth
(plateau stage). This disorder is also associated in seed from plants
affected by psyllid yellows (caused by toxin injected by potato
psyllid) and aster yellows (caused by mycoplasma injected by aster
leafhopper).
External
Appearance:
A
small thin sprout grows prior to normal dormancy break.
Diagnostic
Method:
External
observation. Cut through eye to detect internal sprouting.
Internal
Appearance:
Premature
sprouting will cause a breakdown of starch to reducing sugars below
the sprouted eye.
Cooking
Appearance:
Chips
and fries will have a brown irregular region along outer edge or
end where the sprouted eye was.
Development:
Hot
conditions late in the season will inhibit dormancy of mature tubers
and push them to sprout. Experiments were reported that short exposure
(few hours) to 100oF is able to induce heat sprouting of mature
tubers. (This has been a concern with summer harvest in hot/dry
States as Kansas.)
Control
Measures:
- Plant
deep.
- Avoid
high setting varieties.
Tuber
Internal Growth Defects: INTERNAL SPROUTING
Internal
sprouting occurs in storage and is characterized by the sprout growing
into the tuber, ingrowing. This can occur from a sprout from an
eye on the underside of the tuber growing up and penetrating it
or from deep eyes when the sprout grows sideways into the tuber.
The tip of the internal sprout is commonly necrotic, brown. When
it occurs, it usually is from an eye with multiple sprouts (rosette).
This disorder occurs primarily with physiologically aged tubers
and occurs when storage temperatures are above 55oF. The two major
causes associated with internal sprouting are application of below
effective levels of CIPC, a sprout inhibitor, and high pile pressure
late in the storage season.
Summary:
Internal Disorders |
