Plant Diseases

RUST C ausative agent : Fungi Ex. Puccinia striiformis, Puccinia sorghi, Puccinia graminis ,[object Object],[object Object],[object Object],[object Object],Microbial Plant Diseases

Fig. Stages in the life cycle of black stem rust of wheat caused by Puccinia graminis . (a) Elongated stem lesions bearing uredospores. (b) Stained section of a wheat stem with a pustule of uredospores breaking though the plant epidermis. (c) Section of a pustule with teliospores. (d) Lesions containing spermogonia on the upper surface of a barberry leaf. ( e) Aecia erupting through the lower epidermis of a barberry leaf. (f) A spermogonium (pycnium) , showing the tiny spermatia (pycniospores) and receptive hyphae. (g) Cross-section of an aecium.

Life cycle of Puccinia graminis

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Symptoms of Common rust are elongate to oval brown pustules on both leaf surfaces which rupture and release red spores

[object Object],[object Object],[object Object],[object Object],DOWNEY MILDEW ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],Downy Mildew in Crucifers

[object Object],[object Object],Radish leaves with downy mildew Cucumber leaf with downy mildew

Seedlings, cotyledons and hypocotyls may become infected and seedling loss can occur. sporangiophore and sporangia of downy mildew ( Peronospora parasitica ) Hyaloperonospora parasitica hyphae and haustoria Conidiospores of Hyaloperonospora parasitica

ERGOT ,[object Object],[object Object],[object Object],[object Object],Figure: Disease cycle of ergot.

[object Object],Ergot sclerotia and barley grain.

Rotate cereals and grasses with nonsusceptible crops for one year or longer. The ergot sclerotia usually do not survive in the soil for more than one year. Therefore, summer fallow or crop rotation to a non-cereal crop for at least one year will help reduce ergot. Deep-plow fields which have a severe ergot infestation to bury the sclerotia. The ergot sclerotia will not germinate if buried more than 1 inch deep. Plant only ergot-free seed to avoid introducing or re-introducing the fungus into the field. Eradicate or prevent wild grasses from reaching heading in fields. Resistant commercial varieties of wheat, barley, rye or cultivated grasses are not available. However, some differences among varieties may occur, and those with long flowering periods may be more frequently infected. ,[object Object]

[object Object],BACTERIAL LEAF BLIGHT ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Bacterial leaf blight of rice The bacterium causing the disease is rod, single, occasionally in pairs but not in chains. Gram negative, non-spore-forming, and devoid of capsules.

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],TOBACCO MOSAIC VIRUS (TMV) DISEASE TMV is an ss RNA virus that infect plants, especially tobacco and other members of the family Solanaceae. ,[object Object],[object Object],[object Object]

Electron micrograph of TMV ,[object Object],Light and dark green mottled areas on the leaves. The dark green areas tend to be somewhat thicker than the lighter portions of the leaf. The leaf mottling is seen more easily if the affected plant surface is partially shaded. Stunting of young plants is common, and often is accompanied by a distortion and fern-like appearance of the leaves. Older leaves curl downward and may be slightly distorted. Certain strains of the virus can cause a mottling, streaking, and necrosis and discoloration of fruits. TMV infected tomato leaf (mottled) & fruit (non-uniform coloration)

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Plant Diseases

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