Rust of wheat is caused by a fungus of which genus?
- A.Puccinia
- B.Ustilago
- C.Fusarium
- D.Claviceps
Correct answer
Explanation
The correct answer is A, Puccinia. The rusts of wheat, named black, brown and yellow after the colour of the pustules they raise on the stem and leaves, are caused by species of Puccinia, and resistance to them was one of the traits selected in the dwarf wheats of the Green Revolution. Option B is wrong because Ustilago causes the smuts, in which the ear is converted into a mass of black spore dust; loose smut of wheat is the standard example, and candidates often swap rust with smut. Option C is wrong because Fusarium species cause wilts, as in pigeon pea and cotton, where the plant droops because the water-conducting tissue is blocked. Option D is wrong because Claviceps purpurea causes ergot of bajra and rye, replacing the grain with a hard body that contains poisonous alkaloids.
Read the full article: Plant Diseases and Their Causes: Notes for Exams
Practice Questions
View allLate blight of potato is caused by which organism?
- A.A virus
- B.Phytophthora infestans
- C.Xanthomonas citri
- D.Meloidogyne incognita
Show answer
The epidemic of the 1840s destroyed the potato crop of Ireland and brought on the famine, and the study of that outbreak by Anton de Bary established plant pathology as a science.
Read the full explanation →Red rot, one of the most serious diseases of sugarcane, is caused by
- A.Colletotrichum falcatum
- B.Ralstonia solanacearum
- C.a phytoplasma
- D.a nematode
Show answer
The correct answer is A, Colletotrichum falcatum, a fungus that rots the internal tissue of the cane, turning it red with white patches and giving it a sour smell, and which spreads mainly through infected setts used for planting.
Read the full explanation →Citrus canker in plants is caused by
- A.a fungus
- B.a bacterium
- C.a virus
- D.a deficiency of boron
Show answer
Citrus canker is caused by a species of Xanthomonas, which enters through wounds, insect punctures and stomata and raises raised corky brown lesions, often with a yellow halo, on leaves, twigs and fruit; it spreads in splashing rain, on tools and on infected nursery plants.
Read the full explanation →Khaira disease of rice is caused by the deficiency of which nutrient?
- A.Zinc
- B.Boron
- C.Molybdenum
- D.Copper
Show answer
In khaira disease the leaves of young rice plants develop rusty brown spots that spread until the crop looks scorched, tillering is poor and growth is stunted; an application of zinc sulphate to the soil or as a foliar spray corrects it, which confirms that the cause is a deficiency…
Read the full explanation →Whiptail disease of cauliflower is caused by the deficiency of
- A.Zinc
- B.Iron
- C.Molybdenum
- D.Manganese
Show answer
Where this micronutrient is short, the leaf blade of cauliflower fails to expand and the leaf is reduced to a narrow, whip-like strip along the midrib, which gives the disease its name; the curd is small or does not form at all.
Read the full explanation →