Diseases of Wheat

UNIVERSITY OF AGRICULTURAL SCIENCES
PAT.301(2+1)
DISEASES OF FIELD CROPS AND
MANAGEMENT
TOPIC:FUNGAL DISEASES OF WHEAT
BY,
NAGENDRA
ALB2099

FUNGAL diseases of WHEAT
Major Fungal disease in wheat……….
1. RUSTS
A. Stem rust
B. Leaf rust
C. Stripe rust
2. LOOSE SMUT
3. KARNAL BUNT
4. POWDERY MILDEW
5. FOOT ROT
6. LEAF BLIGHT

Rusts
– Three forms rusts can affect wheat (all fungal
forms)
Stem rust
Leaf rust
Stripe rust

• BLACK or STEM RUST
Pathogen: Puccinia
graminis tritici
Uredospores are brown
and oval
Each cell of teleutospore
has one pore
Size is about 25-30x15-
20µm

• SYMPTOMS:
 Reddish brown pustules
 The large number of
uredosori burst, release
their spores
 Infected parts bursting to
expose a mass of brown
uredospores
 Brownish appearance even
from a distance

Favorable conditions
o Temperature: Between 23-25° C
o In this condition large number of teliospores are
produced.
Alternate hosts
Berberis,
 Mahonia and
 Mahoberberis

Leaf Rust (Brown or
Orange Rust)
Pathogen: Puccinia recondita
 The pathogen is macrocyclic
rust.
Uredospores are brown and
spherical
16-28um in diameter

• SYMPTOMS:
The black telial pustules
are usually formed on the
dorsal side of leaves
The pustules burst early
with mild displacement of
the host epidermis
And deeply embedded into
the host.

Stripe Rust(yellow rust)
Caused by: Puccinia striiformis
 Uredospores are spherical to
ovate in shape
Uredospores are orange
colored.
Size measuring from 23-35x20-
35µm
Teleutospores are dark brown
and flattened at the top when
in contact with the epidermis

Symptoms
 appear early in the
spring.
 Rust pustules are
yellow.
 Spores are blown in
from warmer areas.
 Disease
development is most
rapid under cool, wet
weather.

Alternate hosts
• Agropyron,
• Bromus etc.
Favorable conditions
 Temperature: 10-15 °C

Difference between stripe rust and leaf
rust

Loose smut of Wheat
 Pathogen: Ustilago tritici(=U.
nuda tritici)
 The teliospores are single
celled and formed irregularly
from fertile hyphae.
 Teliospores are olivaceous
brown, spherical to oval
 Measures 5-9µm in diameter

SYMPTOMS:
 Can only be seen at the time
of flowering though the plants
are infected right after seed
germination.
 Ears of infected one emerge
early than healthy one.
 and transformed into black
powdery mass
 Whole ear is covered by
delicate silvery membrane.
 Resulting in formation of very
dark olive brown powdery mass

• Kernel bunt
• Pathogen: Neovassia indica
 Spores are smooth walled
 Measuring 22-49µm in
diameter
 Requires long rusting period
 The primary sporadia are
needle shaped and flexible
 The secondary sporadia are
sickle shaped

• SYMPTOMS:
Plants ripen early than the
healthy one
Ears are dark green
The glues are pushed apart
by the spore balls which
are formed instead of
kernels

• POWDERY MILDEW
• Pathogen: Erysiphe graminis
var. tritici
• The conidia are elliptical,
hyaline, single celled, thin
walled and produced in
chains
• Fungus produce septate,
superficial, hyaline mycelium
on leaf surface with short
conidiophores

• SYMPTOMS:
 Greyish white powdery
growth appears on leaf,
sheath, stem and floral
parts
 Powdery growth later
become black lesion and
 Drying of leaves and
 Other parts

 Fungus remains infected in plant debris as dormant
mycelium
 Favorable temperature is 20-21°C and High RH

• FOOT ROT
Pathogen: Pythium
graminicolum and P.
arrhenomanes
This fungus produces
sporangia, zoospores and
oospores.

• SYMPTOMS:
 The disease mainly occurs
in seedlings
 Roots and rootlets become
brown in color
 Seedlings becomes pale
green and have stunted
growth
 Wet weather and high
rainfall is favorable

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