Microbes and Plant Diseases

Pythium insidiosum is the causative agent of swamp cancer (especially in horses), mainly in wet tropical environments. Infections are characterised by tumour-like masses, which develop mostly on the legs.

A. flavus is the major producer of carcinogenic aflatoxins in crops worldwide.

This is a bacterial disease, which attacks seedlings as they emerge. It thrives in wet, poorly drained and cool soils.

Puccinia graminis tritici belongs to basidiomycotina and causes black rust of wheat. It is internal obligate parasite. It is found everywhere, where wheat is grown. The teleutospore of the fungus causes the rust. They are produced inside teleutosori. These telia form elongated, dark brown to black pustules on the surface of stems and leaves of the wheat.

Association between roots of higher plants, e.g., pine, birch and fungal hyphae is called mycorrhiza. It exhibits the phenomenon of symbiosis. Here both the organisms in association are mutually benefitted. In this, fungal hyphae take nutrition from the plant and in return increase surface area for absorption of water and minerals for the plant. Mycorrhizal roots occur in superficial layers of the soil.

Ceratium furca blooms because of coastal eutrophication. Blooms of this species cause toxic red tides (red-brown), damage fish gills and deplete dissolved oxygen causing anoxic conditions.

Phytophthora spp. are mostly pathogens of dicotyledons and are relatively host-specific parasites. Many species of Phytophthora are plant pathogens of considerable economic importance. Phytophthora infestans was the infective agent of the potato blight that caused the Great Irish Famine.

This fungi is usually isolated as a saprophytic contaminant. World-wide, known as an insect parasite. Sympodial development of single-celled conidia on a narrow geniculate or zig-zag rachis emanating from a flask-shaped conidiophore.

 There exists a close association between the alga and the fungus within a lichen. The fungus provides protection, anchorage and absorption for the alga.This association is known as symbiosis.

Spores are released into the air when the sporangium wall breaks open. The sporangium is a specialized structure that contains spores. When mature, the sporangium ruptures, releasing numerous spores that can be dispersed by wind to new locations for germination.

This is the correct option. Aspergillosis is a disease that is caused by a fungi.

Black piedra is a superficial fungal infection of the hair shaft caused by Piedra hortae forming hard black nodules on the shafts of the scalp, beard, moustache, and pubic hair.

Athlete's foot, also known as ringworm of the foot, or tinea pedis, is a fungal infection of the skin that causes scaling, flaking and itch of affected areas. It is caused by fungi in the genus Trichophyton. The fungus genus Trichophyton is characterized by the development of both smooth walled macro and microconidia. Trichophyton rubrum is a fungus that is the most common cause of athlete's foot, jock itch and ringworm.

Rafflesia is a total root parasite. It is completely dependent upon host root for food, water and minerals.

This option is correct beause violet root rot is caused by Helicobasidium mompa.