Tuber Internal Growth Defects: BROWN CENTER & HOLLOW HEART
Brown center and hollow heart are two facets of the same disorder but can occur independently of each other. Exact causes are not known. This disorder is mostly associated with excessively rapid tuber growth after a cool temperature and moisture stress. An association of stem-end hollow heart with potassium deficiency has also been reported.
There is no outer way to detect it.
Cut longitudinally from end to end.
Brown center is characterized as a small one-eighth to one inch diameter, brown, circular or elliptic, opaque area with a diffuse border along the longitudinal tuber axis. In round to oval tubers, its usually at the tubers center; with long or oblong tubers, there may be two brown areas, one at each end. Brown areas are distinct but have a smooth, gradual change to unaffected tissue. Depending on the speed of growth resumption after stress, brown center may or may not develop into hollow heart. Hollow heart appears as a lens- or star-shaped, irregular cavity in the center of round tubers such as Atlantic or at either or both stem and bud ends of long tubers such as Russet Norkotah. The internal walls are white to tan. The cavity is larger with larger tubers and is mostly seen in very large tubers. No rot is associated with the disorder.
Brown center will boil and fry dark, and hollow heart will leave a cavity after boiling or baking, a hole after chipping, and shorter fries after cutting. US Grade A for table stock potatoes allows for up to dime-size cavities.
Development: Brown center is initiated in small tubers from initiation to two ounces. Cool soil temperature, <56 degrees F, and high soil moisture, >80% available, at tuber initiation and a few weeks thereafter enhances brown center. First, there is a light brown appearance resulting from dead cells near the tuber's center. If, after a moisture stress and formation of brown center, tuber growth is gradually resumed, the surviving cells intersperse between the dead cells and a cavity is not formed. If tuber growth is resumed rapidly, the dead cells split apart forming a cavity and the disorder hollow heart. Fast-growing and very large tubers are more likely to show this disorder. Stem-end hollow heart usually follows brown center and may occur in small tubers. Bud-end hollow heart occurs late in the season and is not often preceded by brown center. Some varieties are less susceptible.
1. Plant closer.
2. Use larger, less aged seed pieces.
3. Establish good plant stands.
4. Avoid plant skips.
5. Apply potassium.
6. Apply nitrogen throughout season (10-20 lb/a weekly).
7. Schedule irrigation for constant and uniform tuber growth.