This document describes the symptoms of various physiological disorders that can occur in potatoes, including black heart, bruising, greening, hollow heart, freezing injury, chilling injury, internal brown spot, black spot, growth cracks, and deficiencies of nitrogen, phosphorus, calcium, magnesium, and potassium. The disorders are described in terms of their visual symptoms, such as discoloration, damage, chlorosis, and necrosis of potato plant leaves, shoots, and tubers. Photos are also provided to illustrate some of the deficiency symptoms.

2. Potato Physiological
Disorders
ToT to FFS Staff
By Mr. Allah Dad Khan
Provincial Coordinator IPM KPK
MINFAL

3. Black Heart
Symptoms
•
Blackheart. Rare in early-crop
potatoes due to typical
marketing practices; In
conditions of restricted airflow
and high respiration, tubers
held above 15°C (rapidly above
20°C) develop an internal
brown discoloration which
eventually becomes deep
black. Insufficient oxygen
reaches the interior of the
tuber under these conditions

4. Bruise and damage
Symptoms
• Bruising or blackspot bruising is caused
when the tuber is impacted. The skin
doesn’t break, but internal tissues are
damaged leading to the formation of
the pigment melanin, which will make
the damaged area appear black, or dark
to light grey. This can be anywhere on
the tuber, but is more prevalent at the
stolon end, and where the tuber is
more curved.
•
• - See more at:
http://potatoes.ahdb.org.uk/media-
gallery/detail/13213/3356#sthash.KrS6
oC0N.dpuf

5. Greening
Symptoms
• Greening. Exposure to bright light
during postharvest handling, or
longer periods (1 to 2 weeks) of low
light intensity, can result in the
development of chlorophyll in the
potato tuber, anatomically a
modified stem. Associated with
greening, bitter and toxic
glycoalkaloids, such as solanine, are
formed. Solanine also forms in
response to bruising, wounding
(including fresh processing followed
by storage), and during sprouting.
Glycoalkaloids are heat stable and
minimally impacted by cooking.

6. Hollow Heart
Symptoms
• Hollow heart and brown
center negatively impact tuber
quality. The disorders make
cut fresh-market tubers
unattractive and can reduce
repeat sales. Severe hollow
heart negatively impacts the
quality of chip-processing
potatoes and can result in
shipments not making grade.
However, neither disorder is
reported as harmful and
neither affects the tuber's
taste or nutrition.

8. Freezing Injury.
• Freezing injury will be initiated at -0.8°C
(30.5°F). Symptoms of freezing injury include a
water-soaked appearance, glassiness, and
tissue breakdown on thawing. Mild freezing
may also result in chilling injury.
• Symptoms

9. Chilling Injury Symptoms
• Chilling Injury. Storage at temperatures near
0°C (32°F) for a few weeks may result in a
mahogany discoloration of internal tissue in
some varieties. Much longer periods of
storage are generally required for chilling
injury

10. Internal Brown spot
Symptoms
• Internal Brown Spot. Internal
dry, corky reddish-brown or
black spots or sectors. Uneven
water management and/or
widely fluctuating
temperatures induce this
calcium uptake deficiency,
usually early in tuber
development. Uneven water
availability may also result in
Hollow Heart, a corky
cavitation at the center of the
tuber

13. Black Spot
Symptoms
• . Responsible for significant
postharvest losses, particularly in
response to over-fertilization with
nitrogen, low soil potassium
availability, irregular irrigation, and
other pre-harvest practices. Non-
pigmented compounds form in the
vascular bundle tissue just under
the skin during storage. Following
severe bruising or cutting, the
affected tuber tissue turns reddish,
then blue becoming black in 24 to
72 hours. Severity increases with
time.Varieties differ significantly in
their susceptibility and symptom
expression.

14. Growth Cracks
Symptoms
• Growth cracking is an external
noninfectious physiological
disorder of the potato tuber in
which the tuber splits while
growing. The split heals but
leaves a fissure in the tuber.
Growth cracks generally start at
the bud or apical end of the
potato and can extend
lengthwise. They vary in severity
from a surface abrasion to a split
through the tuber, depending on
the stage of growth during which
the initial cracking occurred
Moderate (left) and severe
(right) growth cracks

15. Potato Plant in Sand Culture
Symptoms
• Complete mineral nutrient
• Growth normal; foliage
healthy green color

16. Potato Plant in Sand Culture Nitrogen
deficiency
Symptoms
• Growth severely restricted,
few stems; yellowing of
older foliage

17. Potato Plant in Sand Culture
Phosphorus deficiency
Symptoms
• Growth thin, few stems;
leaflets marginal scorch,
older leaves shed

18. Potato Plant in Sand Culture Calcium
deficiency
Symptoms
• Growth fairly good; bushy
appearance; young leaflets
small, slightly chlorotic,
forward roll and marginal
scorch. This plant failed to
form tubers of appreciable
size.

19. Potato Plant in Sand Culture
Magnesium deficiency
Symptoms
• Growth fairly normal;
foliage slightly pale; older
leaflets develop central
necrosis, turn yellow or
brown and wither
prematurely

20. Potato Plant in Sand Culture
Potassium deficiency
Symptoms
• Growth tends to be squat
and bushy; leaflets bluish
green and slight intervenal
chlorosis, marginal scorch
and brown spots on under
surface.

21. Potato Leaves Nitrogen deficiency
Symptoms
• Right: nitrogen deficient
leaf, pale green and yellow
tinted, contrasted with left,
normal green leaf with
ample nitrogen supply

22. Potato Leaf Phosphorus deficiency
Symptoms
• Leaflets, lustreless green,
marginal scorch and
forward curling of margins

23. Potato Shoots Calcium deficiency
Symptoms
• Acute deficiency condition.
Shoots become thin;
leaflets of terminal leaves
small, margins chlorotic,
incurled and may develop
faint pink tints or necrotic
brown spots or scorch; tips
of leaflets die.

24. Potato Plant Calcium deficiency
Symptoms
• Field plant. Bushy growth
habit, thin shoots, small
terminal leaves and
scorched leaflets.

25. Potato Plants Calcium deficiency
Symptoms
• Field view showing calcium
deficiency induced by
heavy potassic manuring
on acid soil. Left
foreground: no potash;
plants bushy and squat,
due to potash deficiency;
Right foreground: heavy
potassic manuring; plants
tall, leaves rolled due to
calcium deficiency

26. Potato Tubers Calcium deficiency
Symptoms
• Top: calcium omitted,
tubers dwarfed and
useless; bottom: complete
mineral nutrient, tubers
normal.

27. Potato Leaf Magnesium deficiency
Symptoms
• Central intervenal necrosis
pattern

28. Magnesium Deficiency — Chlorosis
and necrosis of leaves, defoliation
Symptoms
• Growth fairly good; foliage
chlorotic and with
intervenal necrosis; death
of older foliage and severe
defoliation

29. Potassium Deficiency — Marginal leaf
scorch
Symptoms
• Growth fairly good; leaves
bluish-green and intervenal
chlorosis, spotting and
marginal scorch present