| | Blackheart | Hollow heart | Malformed tubers | Low temperature injury
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Blackheart
Blackheart results from an insufficient oxygen supply to internal tuber tissue. The centre of the tuber turns blue-black. The tuber tissue associated with blackheart remains firm, as opposed to the black, soft watery tissue resulting from leak infection. Blackheart may develop if tubers are held in low oxygen environments. This can occur in less than ideal storage conditions, water logged soils, or if condensation forms on tubers. Blackheart is prevented by proper ventilation, storing at recommended temperatures, and improvement of soil drainage.
Hollow Heart
Hollow heart, a cavity near the centre of the tuber, results from rapid tuber growth. The disorder is found primarily (but not only) in large potatoes. Walls of the cavities are white to light brown. The disorder is difficult to detect because affected tubers have no external symptoms. They can only be removed with expensive X-ray grading equipment. Hollow heart is promoted by growing conditions that cause rapid tuber enlargement. Poor stand increases the incidence of hollow heart.
To reduce hollow heart:
- Plant susceptible varieties at closer spacings. See Variety Descriptions for details on varietal susceptibility.
- Maintain uniform soil moisture throughout the entire growing season
- Plant to maximize stand of uniform plants and minimize misses
- Ensure adequate potassium fertility
Malformed Tubers
Extreme soil temperatures may cause secondary growth, knobs, and other tuber deformities. Other conditions such as nutrient and water imbalances have also been implicated in irregular tuber development. Growth cracks may arise from rapid tuber growth and are often the result of improper fertilizer placement.
To prevent or reduce malformed tubers:
- Maintain uniform soil moisture, particularly during tuber development
- Apply recommended fertilizer rates
- Establish a high stand of uniform plants to control tuber growth rates
- See Variety Descriptions for details on varietal susceptibility
Low Temperature Injury
Low temperature or freezing injury can occur to potatoes that are exposed to a heavy field frost or to tubers that
have been excessively chilled in storage. Frozen tissue, upon thawing, discolours and breaks down into a soft watery mass (Plate 33). Chilling injury often results in streaks of discolouration in the vascular tissue of the tuber. Frozen or chilled potatoes should not be used for seed as cut surfaces may not heal and seed piece decay will result
Low temperature injury losses can be reduced or prevented by:
- Storing at temperatures above 37°F (3.0°C)
- Proper ventilation and temperature control. See Special Storage Problems for more details.
- Culling frozen potatoes prior to storage
Written by Tracy Shinners-Carnelley, Piara Bains, Debbie McLaren, Jill Thomson |
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