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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 WHEATMajor Fungal disease in wheat……….

1. RUSTS A. Stem rust B. Leaf rust C. Stripe rust2. LOOSE SMUT3. KARNAL BUNT4. POWDERY MILDEW5. FOOT ROT6. LEAF BLIGHT

Rusts

– Three forms rusts can affect wheat (all fungal forms)

Stem rustLeaf rustStripe 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 hostsBerberis, Mahonia and Mahoberberis

Leaf Rust (Brown or Orange Rust)

Pathogen: Puccinia recondita

The pathogen is macrocyclic rust.Uredospores are brown and spherical16-28um 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-

35µmTeleutospores 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