What are the parasitic agent of plant disease?

Parasitic agents of plant disease

Parasitic agents are organisms that live on or in a host organism and derive their nutrition from that host. In the case of plant diseases, the parasitic agents are typically fungi, bacteria, viruses, or nematodes.

Fungi

Fungi are the most common type of parasitic agent of plant disease. They include a wide range of organisms, from microscopic yeasts to large, fleshy mushrooms. Fungi cause a variety of diseases, including leaf spots, wilts, and rots. Some of the most common fungal plant pathogens include:

* _Botrytis cinerea_, which causes gray mold on grapes, tomatoes, and other crops

* _Fusarium oxysporum_, which causes wilt in bananas, cucumbers, and other crops

* _Phytophthora infestans_, which causes late blight in potatoes and tomatoes

* _Rhizoctonia solani_, which causes damping-off in seedlings and root rot in many crops

Bacteria

Bacteria are single-celled organisms that are found in soil, water, and the air. They can cause a variety of diseases in plants, including blights, wilts, and rots. Some of the most common bacterial plant pathogens include:

* _Agrobacterium tumefaciens_, which causes crown gall in plants

* _Clavibacter michiganensis_, which causes bacterial wilt in cucumbers, tomatoes, and other crops

* _Erwinia amylovora_, which causes fire blight in apples, pears, and other rosaceous plants

* _Pseudomonas syringae_, which causes bacterial leaf spot in a variety of crops

Viruses

Viruses are acellular agents that can only replicate inside the cells of a living host. They can cause a variety of diseases in plants, including mosaics, yellowing, and stunting. Some of the most common viral plant pathogens include:

* _Cucumber mosaic virus_, which causes mosaic in cucumbers, tomatoes, and other crops

* _Tobacco mosaic virus_, which causes mosaic in tobacco, tomatoes, and other crops

* _Tomato spotted wilt virus_, which causes a wilt in tomatoes, peppers, and other crops

Nematodes

Nematodes are small, roundworms that live in soil. They can cause a variety of diseases in plants, including root rot, stunting, and yellowing. Some of the most common nematode plant pathogens include:

* _Meloidogyne incognita_, which causes root-knot nematodes in a variety of crops

* _Pratylenchus penetrans_, which causes lesion nematodes in a variety of crops

* _Xiphinema index_, which causes dagger nematodes in grapes, peaches, and other crops