Download Plant Disease Symptoms – Hill Agric

Plant Disease Symptoms
Pl. Path. 111 (Cr. Hrs. 3+1)
P.N. Sharma
Department of Plant Pathology,
CSK HPKV, Palampur (H.P.)
symptom and Sign

Symptom – are the expression of the disease caused by the
manifestation of the physiological reaction of the plant due
to harmful activity of the pathogen
Sign - physical evidence of the presence of disease
agent (e.g., mold or fungal spores, bacterial ooze)
Syndrome
Defined as sequential appearance of disease
symptoms on a plant during the development of the
disease or sum total of symptoms exhibited by a
disease
Fleck or necrotic spot
Uredial pustule
Telial pustule
Death of organ or plant
Local infection:
An infection affecting a limited part of a plant e.g. leaf
spot.
Systemic infection:
infection that spread point of infection to different parts
of the plants e.g. wilts, virus infection, loose smut
Lesion
A localized necrotic or chlorotic areas of diseased
tissue/ organ.
Local lesion:
A localized spot produced on a leaf upon mechanical
inoculation with a virus.
Types of symptoms
Morphological symptoms
Histological symptoms
Morphological symptoms
• Morphological:
(Externally
detectable
symptoms caused by any pathogen e.g.
blight, leaf spot
– Necrosis
– Hypoplasia
– Hyperplasia & Hypertrophy
Morphological: (Externally detectable
symptoms caused by any pathogen e.g.
blight, leaf spot
– Necrosis
– Hypoplasia
– Hyperplasia & Hypertrophy
Necrosis
degeneration of protoplast followed by death of the
tissue or organ or plant
• Plesionecrosis
(Nearly dead): necrotic symptoms
expressed before the death of the protoplast are called
plesionecrosis.
E.g. yellowing, hydrosis, wilting
• Holonecrosis: necrotic symptoms expressed after the
death of the protoplast are called holonecrosis. In this the
affected tissue turns brown in colour
E.g. Rots, spots, blights
Plesionecrotic symptoms
• Yellowing:
• Wilting:
• Hydrosis:
Yellows/ yellowing
Appearance of uniform or
non-uniform yellowing of
leaves due to infection.
it is the result of breakdown of
the chlorophyll
e.g. by fungi (e.g., celery yellows), viruses
(e.g., sugar beet yellows virus),
bacteria (e.g., coconut lethal yellowing),
protozoa (e.g., hart rot), spiroplasmas or
phytoplasmas
Browning of vascular tissues
Wilt
Wilt:
A symptom characterized by loss of turgor, which results in
drooping of leaves, stems, and flowers.
e.g. bacterial wilt of tomato
Pathological wilt: caused by pathogen-fungus, bacteria and
viruses
Physiological wilt: due to water stress and high temperature
Hydrosis: appearance of water soaked trnasluscent
diseased tissues whose intercellular spaces contains
liquid. This type of symptoms precedes holonecrotic
symptoms
Holonecrotic symptoms
May develop on any part of the plant and generally the
infected tissues turns brown.
• Holonecrotic symptoms can be divided into three
categories
– Necrosis of the green plant parts
– Necrosis of the storage organs
– Necrosis of woody tissues
• Necrosis of the storage organs
– Rots
– Leak:
– Mummification:
Necrosis of the green plant parts
leads to formation of number of disease
symptoms like:
• Restricted necrosis
– Damping off
– Spots
– Shot holes
– Speck or fleck
– Blotch
– Streaks
– stripes
Damping-off
• Is the collapse and death of
seedlings due to extensive
necrosis of stem tissues before
or after they emerge from the
soil (pre-emergence and postemergence
damping-off,
respectively).
•caused by Pythium and
Rhizoctonia ,
Angular leafspot of beans
Septoria leafspot of tomato
Leaf spot: A wll defined or self-limiting grey,tan or brwon
necrotic lesion on a leaf
Veinal necrosis and local lesions
BCMNV
Shot hole. When a necrotic tissue with in a
leafspot cracks and fall off, leaving small
holes in their place
Shot hole of Cherry: Coccomyces hiemalis
Blotch:
A necrotic area covered with brown fungus mycelium
on leaves, shoots, and stems
Purple Blotch of garlic:
Alternaria porii
Streaks & Stripe
Maize Streak- MSV
Barley stripe
Drechslera graminea
Necrosis of woody tissues
• Die back: extensive necrosis of shoots
from top/ tip to down ward e.g. die back
of chilli/ citrus
• Cankers: Necrosis of the bark tissues e.g.
citrus canker
• Gummosis: Oozing of gum like secretions
from the woody tissues: Gummosis of
stone fruits
• Guttation:
Die back: extensive necrosis of shoots from top/ tip
to down ward e.g. die back of chilli/ citrus
Canker:
• Formation of sharply delineated,
dry, necrotic, localized lesions on
the stem due to death of
cambium tissue of bark, or (in
non-woody plants)
Cankers
Bacterial canker of tomato
Stem canker
Nectria canker on apple
Gummosis:
A plant disease in which the lesions exude a sticky
liquid.
ooze from bacterial canker (apricot) is milky in color
Guttation:
Exudation of water from plants,
particularly along the leaf margin
Extensive necrosis
•
•
•
•
•
•
Blights
Scald
Scorch
Blast
Anthracnose
Firing
Blight:
• A disease characterized by rapid and extensive death (Necrosis)
of plant foliage.
• A general term applied to any of a wide range of unrelated
plant diseases. (e.g., chestnut blight, fireblight, late blight, halo
blight)
Late blight of Potato
Bacterial blight of beans
Blast : it is sudden death of unopened bud or inflorescence
Rice blast: Magnaporthe gresia
Anthracnose:
Formation of discrete, darkcolored, necrotic lesions on
the leaves, stems, and/or
fruits.
Caused
by
fungus:
Colletotrichum spp.
Bean anthracnose:
C. lindemuthianum
Chili anthracnose:
C. capsici
Fire blight of apple: Erwinia amylovora
Necrosis of the storage organs
–Rots
–Leak:
–Mummification:
Rot:
Buckeye Rot of tomato
The softening, discoloration, and often decay or
disintegration of a succulent plant tissue as a
result of fungal or bacterial infection.
Root & Fruit Rots
ROOT ROT
Leak: exudation of juice from tissues with soft
rot is called leak
Infected apple fruit exuding
droplets of fire blight
bacteria.
Mummification
Drying of the rotted organs resulting in
shriveling and hardening like mummies
brown rot fungus (Monilia fructicola)
causes mummification the peach fruits
Hyperplastic & Hypertrophic symptoms
Hyperplasia:
A plant overgrowth due to increased cell division.
Hypertrophy:
A plant overgrowth due to abnormal cell
enlargement.
• Wound tumors,
• Galls
• Witches Broom
• Enations
Tumor:
An uncontrolled growth of tissue or tissues
Gall:
• An
abnormal
plant
structure
formed
in
response to parasitic attack
by certain microorganisms
(bacteria, fungi, viruses) or
insects.
• Galls may develop either
by
localized
cell
proliferation or increase in
cell size.
Crown galls on peach;
Agrobacterium tumefaciens
Hyperplastic &
Hypertrophic
Hyperplasia:
A plant overgrowth due
to increased cell division.
Hypertrophy:
A plant overgrowth due to
abnormal cell enlargement.
Crown gall/ tumor
Enation
A symptom caused by certain plant viruses in which
there are small outgrowths on the plant
Leaves of pea (Pisum sativum cv. Dark Skinned Perfection) infected
with Pea enation mosaic virus (PEMV)
Witches„ broom
An abnormal form of plant growth
characterized by profuse outgrowth of lateral
buds to give a broom like appearance.
Potato witches’ broom
Groundnut witches’ broom
Hypoplastic symptoms
• Atrophy/ Hypoplasis/ dwarfing/ Stunting
• Rosette: in this the internodes do not enlarge and leaves
are clustered like petals of rose e.g. Peach rosette,
ground rosette
• Albication: Complete repression of colour caused by
viruses, bacteria, fungi, and iron deficiency
• Mosaic; appearance of dark green and light green
areas on leaves e.g. Tobacco mosaic
• Chlorosis: failure of chlorophyll to develop fully.
Atrophy or stunting or Dwarfing
Corn stunt
• Chlorosis:
The
loss
of
chlorophyll from the
tissues of a plant,
resulting
from
microbial infection,
e.g. viral infection, the
action of certain phytotoxins,
the lack of light, to
magnesium
or
iron
deficiency, etc. Chlorotic
tissues commonly appear
yellowish
Chlorosis & Chlorotic ring
spot by BCMV
Rosette:
An abnormal condition in which the leaves form
a radial cluster on the stem.
Groundnut rosettee caused by: Groundnut rosette umbravirus
yellow mosaic
MYMV
Mosaic
BCMV
Mosaic:
Appearance of dark green,
light green pattern or sometimes
chlorotic areas on leaves due to
virus infection
Golden mosaic CpGMV
Histological Symptoms:
(can be detected microscopic studies
of the disease sample/ tissue) also
called Pathological anatomy or
Morbid anatomy
e.g. Cuticle thickness, cell wall
degeneration etc.
Tylose formation in xylem
vessels due to wilt
General Disease symptoms
Downy mildew:
Formation of superficial cottony hyphal growth with
spores generally on under side of the leaf
DOWNY MILDEW (Peronospora parasitica)
Powdery Mildew
Apple scab (Fruit)
Scab:
roughened,
crust
like diseased area on the
surface of a plant organ
(e.g., apple scab, potato
scab, wheat scab).
Apple scab (Leaf)
COMMON SCAB (Streptomyces species)
a
Vein clearing a) and Chlorotic ringspot (b) symptoms due
to BCMV in common bean
Vein clearing:
A symptom of virus-infected leaves in which
veinal tissue is lighter green than that of healthy.
Epinasty:
Downward curling of a leaf blade resulting
from more rapid cell growth on the upper side
of a petiole than on the lower side; often a
hyperplastic symptom of plant disease
Green Vein banding
Vein banding:
A symptom of virus-infected leaves in which tissues along the veins
are darker green than other laminar tissue.
Golden mosaic of cowpea
Leaf curl of
tomato
Ergot:
• Sclerotia that replaces the grain in a diseased
inflorescence
• Disease of certain grasses and cereals,
especially rye, caused by Claviceps purpurea
Honeydew stage
Typical Leaf roll of lower leaves
Smut:
Appearance of masses of dark, powdery, and
sometimes odorous spores on inflorescence
e.g. stinking smut of wheat, common smut of
maize.
White Mold/ rot of
Beans
Mold :
A downy fungal growth on rotted or decaying
host tissue, usually consisting of mycelium.
e.g. grey mold of chickpea
Rust
Rust A disease giving a “rusty” appearance to a
plant and causal agents form rust-colored spores
Pustule
Small blister-like eruptions on the leaf epidermis
created by spores formed underneath and push
outward.
WHITE RUST (Albugo candida)
b
Ring spot:
Appearance of single or concentric rings of
discoloration or necrosis, the regions between
the concentric rings being green. The center of
the lesion may be chlorotic or necrotic
Stem-pitting:
A
symptom of some
viral
diseases
characterized
by
depressions on the
stem of the plant
Stem pitting in
apple
Sooty mold:
Appearance of dark, spongy, hyphal mats on the
surfaces of certain plants due to organisms that
grow on honeydew.
Dodder infection
Scorch: "Burning" of leaf margins as a result of
unfavorable environmental conditions (high temperature)
Iron Deficiency
Acknowledgements
• I gratefully acknowledge the use of some very
important photographs given in text book
“Plant Pathology” by G N Agrios.
• I also acknowledge the scientists who spent
valuable time in generating information on
various aspects of plant pathology and
displayed the same on internet for use by
students, teachers and researchers
• Lecture dedicated to respected “G N Agrios”