Question

Blast of rice is caused by
(a) Fungus
(b) Virus
(c) Protozoa
(d) Bacteria

Answer 1

Hint: Organisms belonging to the class Ascomycetes that infect many crops mainly plants that produce cereals characterized by harpophora-like asexual morphology.

Complete answer:
Magnaporthe grisea is a plant pathogenic fungus that belongs to the phylum Ascomycota. This fungus infects many agricultural important plants like wheat, rice, rye, millet, etc. It causes a disease called blast disease or blight disease. If this fungus attacks rice plants, it results in a disease called blast of rice. The blast of rice is also called rice blast.

Additional Information: - Every year, annual crop loss of paddy is due to the blast of rice caused by a fungus
- This fungi can reproduce both sexually and asexually
- Appressoria and hyphae are the specialized infective structures produced by the fungus that infects aerial tissues and root tissues
- Plants affected by blast or rice show initial symptoms like white to grey lesions on the shoot, dark spots are also seen on the shoot. Cells in the edges of the leaves are dead and appear in brown.
- Banded patterns are observed in the internodal region. Plants affected with this disease produce less number of seeds when compared to the normal plant.
- Excessive use of nitrogen as fertilizer results in pathogen infection
- Both chemical treatment and genetic treatment provide resistance for the plant against fungi that cause a blast of rice
- Carpropamid is a chemical that helps in the prevention of appressoria penetration into epidermal cells leaving the grains unaffected
So, the correct answer is 'Fungus'.

Note: rice strains such as M-201, M-202, M-204, M-205, M-103, M-104, S-102, L-204, Calmochi-101 show rice blast disease, among them rice strain M-201 is most vulnerable.
Rice blast fungus, rice rotten neck, rice seedling blight, rye blast, oval leaf spot of Gramineae, johnson spot are other names for Magnaporthe grisea.