Diseases caused by ergot fungus,Xanthomonas oryzae,Phytophthora infestans,Puccinia graminis and Plasmodium falciparum

Claviceps purpurea (ergot fungus) causes ergotism in rye. The ear of rye develops sclerotium of the fungus and contains hallucinogen such as LSD ( dIethy lysergic acid).LSD induces chronic psychosis and severe damage to the central nervous system in human and other mammals.

Xanthomonas oryzae cause the bacterial leaf blight of rice. It is a bacterium which is gram-negative, aerobic, capsulated, and motile with a single polar flagellum.Primary infection is carried through the infected seeds. The entry of the pathogen occurs through wounds and stomata. The symptoms of the disease are the appearance of linear, yellow to straw colored stripes, usually on both the edges of the leaf. As the disease progresses, the drying and twisting of the leaf tip occur. The most destructive phase of the disease is the ‘Ikresek’ or wilt resulting from early systemic infections.

Pythophthora infestans cause late blight of potato disease. It is a Phycomycetes fungus. Alternaria solani is the causal organism of early blight of potato disease.

Puccinia graminis cause Black stem rust. The genus Puccinia includes 700 species, which cause rust diseases of many economic plants such as wheat, barley, oats, etc.

It is called a rust because of the reddish brown color of the spores that are found chiefly upon the surface of the host leaves and stem. P. graminis is heteroecious, i.e., requiring two hosts, wheat, and barbery for the completion of the normal life cycle.

According to the nature of the spores, the life cycle of the P. graminis is divided into five stages. It is during, teleuto stage, the teliospore (or teleutospores) produce dark brown to black pustules on the surfaces of stem and leaves of the wheat that results into ‘black stem rust of wheat’.

1. They are obligate parasite causing rust disease.

  • P.  graminia tritici cause black stem rust of wheat.
  • P.striiformis  cause yellow rust of wheat.
  • P. recondita causes orange rust of wheat.

2.The black stem rust of wheat produce five types of spores:

  • On wheat – Urediospores, Teleutospores, and Basidiospores.
  • On barberry – Pycniospores, and Aeciospores.

3. Rusts are called as heteroecious when they need two hosts to complete their lifecycle. The rusts which need one host to complete their life cycle are called autoecious.

4. Uredospores are formed on wheat and are dikaryotic.

5. Teleutospores are also formed on wheat and in the beginning, they are dikaryotic, later on, dikaryon fuses to form synkaryon.

6.Pycniospores or spermatia are produced in spermogonium or pycnium on monokaryotic mycelium in barberry leaves.

7.Aeciospores are produced on barberry leaves on dikaryotic mycelium in aecium.

Plasmodium falciparum is a parasite protozoan that causes malaria in humans. It is one of the species of Plasmodium.Being digenetic, it’s life cycle is complete in two hosts man and mosquito.

Its sexual cycle is completed in female Anopheles mosquito, and infective individuals called sporozoites are formed. Sporozoites are transmitted to humans by the biting of infected female Anopheles. The asexual cycle is passed in man in two phases. Malaria caused by P.falciparum (also known as asetivo-autumnal, malignant tertian or pernicious malaria) causes the most dangerous form of malaria, with the highest rate of complication and mortality. In this case, fever cycle is 48 hours and is often fatal to the patient as it affects the brain.

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