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Bacterial and viral diseases ofWheat

Nagendra,S.R.ALB2100

Contents

Bacterial Diseases

Yellow Ear Rot Black

chaff/Bacterial streak

Bacterial leaf blight

Viral DiseaseS

Wheat Soil borne Mosaic virus

Wheat streak Mosaic Virus

1)Yellow Ear Rot / Tundu Disease

Pathogen: Clavibacter tritici (the disease is known to occur only in association with nematode ( Anguina tritici )

The bacterium is spherical , gram positive and capsulated.

SPREAD: Seeds contaminated with nematode galls are responsible for the spread of the disease.

The disease is characterized by twisting, distortion of earhead and rotting of spikelet's, with profuse oozing of yellow liquid from the infected tissues.

Symptoms

2)Black chaff = bacterial streak

• Pathogen: Xanthomonas translucence pv. undulosum

•Favorable Environmental Conditions:

Black chaff is favored by wet and humid weather.

Symptoms:

Discoloration of glumes on a mature white headDark purple discoloration of wheat stem

BACTERIAL LEAF BLIGHT

• Pathogen: Pseudomonas syringae pv. syringae

• Favourable conditions : Moist and mild weather during flag leaf emergence.

• It can tolerate warm or freezing temperature.

• Free moisture is required for disease development.

Symptoms:

Start as narrow chlorate lesions on leaves, turn yellow and then dark brown When moist, a water soaked appearance from the bacterial exudate I.e. sticky yellowish colors.

VIRAL DISEASES:

Wheat Soil borne Mosaic Virus

Wheat Streak Mosaic Virus

1)Wheat soil borne mosaic virus

• Pathogen: Wheat yellow mosaic virus (WYMV)

• Conditions: Long periods of fluctuating temperatures in early spring.

• Transmission: Soilborne fungal vector (Polymyxa graminis) and sap transmission

Polymyxa graminis,is the reported vector of wheat soil borne mosaic virus is an obligate root parasite of wheat.

Symptoms:Yellow green mosaic on young leaves, stunting, severe rosetting and excessive tillering.

This virus is transmitted by soil borne fungi.

2)Wheat streak Mosaic Virus

Transmission: Eriophes tulipae(Wheat curl mite)Alternate hosts: Maize, oats, barley, wild grass

Mosaic streaking all along the veins, the infested plants produce fewer or less tillering and stunted growth.

Symptoms:

• Infects both winter and spring wheat.

• Earlier infection = greater yield loss.

• Grassy weeds, volunteer wheat, corn, etc. can harbor both WSMV and the mite vector.

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