| Tuber
Internal Growth Defects: INTERNAL HEAT NECROSIS
Internal
heat necrosis is associated most with high temperatures at harvest,
acid soils and low calcium. Most affected are certain chipping varieties
most notably Atlantic. Low soil moisture may have a role.
External
Appearance:
There
is no outer appearance change. Reports have indicated that spindly
sprouts may form from affected seed pieces.
Diagnostic
Method:
Cut
transverse, cross-sectionally, through center and at bud end.
Internal
Appearance:
The
necrosis appears as light tan, dark yellow to reddish brown flecks
or specks; these may be dark brown or black in the most severe cases.
They resemble the necrosis seen with chilling injury. Flecks usually
cluster near the center toward the bud end and can appear similar
to blackheart. The flecks are firm; there's no breakdown or rot.
Vascular tissue is usually not affected but, in some cases, flecks
may be confined to the vascular tissue at the bud end.
Cooking
Appearance:
Flecks
fry brown. Fries and chips will be speckled around their center.
Development:
This
disorder is initiated as a result of harvesting during high temperatures
and develops in storage over the first few months. Tubers near the
ground surface are most affected. Heat necrosis is most common during
hot and dry seasons and with potatoes planted in light soils. Low
tuber calcium has been correlated with this disorder; whether a
cause or result isn't clear.
Control
Measures:
- Add
lime to acid soils.
- Add
of calcium to deficient soils.
- Establish
good vine growth to shade ground (row closure).
- Don't
store tubers in ground long after vine death.
- Schedule
irrigation for seasonal growth.
Summary:
Internal Disorders
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