| 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.
External
Appearance:
There
is no outer way to detect it.
Diagnostic
Method:
Cut
longitudinally from end to end.
Internal
Appearance:
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.
Cooking
Appearance:
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.
Control
Measures:
- Plant
closer.
- Use
larger, less aged seed pieces.
- Establish
good plant stands.
- Avoid
plant skips.
- Apply
potassium.
- Apply
nitrogen throughout season (10-20 lb/a weekly).
- Schedule
irrigation for constant and uniform tuber growth.
Summary:
Internal Disorders |
