Biotic Diseases

Biotic Diseases

They can be caused by: 1. Nematodes2. Viruses3. Bacteria4. Parasitic higher plants5. Fungi

Plant diseases caused by nematodes

Soybean cyst nematodesHeterodera glycines

Stem and bulb nematodesDitylenchus dipsaci

Nematodes are wormlike in appearance but taxonomically different from true worm.

They live freely in fresh or salt waters or in soil and feed on microorganisms, plants and animals.

1.Soybean cyst nematodesHeterodera glycines

Plant: SoybeanParasite: Heterodera glycines

Symptoms:

The root system of the infected plants appears smaller with fewer bacterial nodules and clusters of cyst nematodes.

Infected soybean are stunted and their leaves turn yellow and fall off early.

2.Stem and bulb nematodesDitylenchus dipsaci

Plant: Stem and bulb of plantsParasite: Ditylenchus dipsaci

Symptoms:

Infected bulb: Curled green leaves and

the scales becomes softened, loose and

pale gray in color.

Infected bulb may be split and become

malformed, odorless and light in

weight.

Infected tuber:lesions appear on the tuber as small brown blemishes. On the cut surface, the underlying tissues appear granular and spongy. The blemishes grow larger and the final stage is expressed by mummification of the tuber.

Plant disease caused by viruses

1.Diseases caused byTobacco mosaic virus

6.Disease caused by Papaya ringspot virus

3.Diseases caused by hordeiviruses

4.Diseases caused by Lettuce mosaic virus

5.Disease caused by sugarcane mosaic virus

2.Diseases caused byTomato mosaic virus

1.Diseases caused by

Tobacco mosaic virus

Disease name: Mosaic virusPlant: TobaccoPathogen: Tobacco mosaic virus

Symptoms:

Various degrees of chlorosis, curling, distortion, dwarfing of leaves, flowers and entire plants.

2.Diseases caused by

Tomato mosaic virus

Disease name: Mosaic virusPlant: TomatoPathogen: Tomato mosaic virus

Symptoms:

Leaflets may be long and pointed, sometimes shoestring-like.

Internal browning of fruits.

3.Diseases caused by

hordeivirusesDisease name: Barley stripe mosaic virus

(BSMV)Plant: Barley (Hordeum spp.), grain crops and

wild grassesPathogen: hordeivirus

Symptoms:

Chlorotic spots, yellow-brown strips and sometimes dwarfing and necrosis of plants.

4.Diseases caused by

Lettuce mosaic virus

Disease name: Mosaic virusPlant: LettucePathogen: Lettuce mosaic virus

4.Diseases caused by

Lettuce mosaic virus

Disease name: Mosaic virusPlant: LettucePathogen: Lettuce mosaic virus

Symptoms:

Mottling (yellowing of leaves), distortion and marginal necrosis of leaves, dwarfing of plant and failure to produce lettuce head.

5.Disease caused by sugarcane

mosaic virusDisease name: Sugarcane mosaic virusPlant: Sugarcane, other gramineae (corn,

sorgum,…)Pathogen: Sugarcane mosaic virus

Symptoms:

Pale patches and twisted

distorted leaves.

Necrotic and stunted stems.

6.Disease caused by

Papaya ringspot virus

Disease name: Papaya ringspot virus Plant: PapayaPathogen:Ringspot virus

Symptoms:

Fruit: Dark green and slightly sunken rings with unpleasant taste.

Yellow mosaic leaves with

stunting of the plant.