Diseases and Treatment: VII. Main Plant Diseases

Total Questions: 20

11. White rust is a prominent fungal disease of [R.A.S./R.T.S. (Pre) 1996]

Correct Answer: (b) Mustard
Solution:

White rust affects mustard, caused by Albugo candida, leading to white lesions on the stem, leaves, and inflorescence, reducing plant productivity. White rust is a significant problem for cruciferous crops like mustard, cabbage, cauliflower, broccoli, and radish.

It can also affect other members of the Brassica family, including arugula, bok choy, and Brussels sprouts. White rust can also infect various ornamental plants. Certain weeds within the Brassica family can also be affected

12. Which among the following statements is not true? [U.P. R.O./A.R.O. (Pre) 2017]

Correct Answer: (c) False smut is a disease found in barley.
Solution:

False smut occurs in paddy, causing chalky grains and reducing seed germination. Other statements are correct. False smut causes individual rice grains to transform into masses of yellow or greenish-black spore balls.

These balls are initially orange but mature into yellowish-green or greenish-black. Only a few grains per panicle are usually infected, but neighboring grains often remain unfilled.

The disease leads to chalkiness in the grains, reducing their weight and quality. Infected grains also have a lower germination rate, making them unsuitable for planting.

False smut is visible only after the panicle (the flowering part of the plant) emerges. The fungus can infect the plant during the flowering stage. The disease can thrive in areas with high relative humidity (over 90%) and temperatures ranging from 25-35°C.

13. Two common fungal diseases of wheat are: [R.A.S./R.T.S. (Pre) 1996]

Correct Answer: (a) Black rust & smut
Solution:Black rust and smut are both fungal diseases of plants, specifically affecting crops like wheat. Black rust, also known as stem rust, is caused by Puccinia graminis and results in reddish-brown or yellow pustules on stems and leaves. Smut, on the other hand, is caused by Ustilago fungi and manifests as black, powdery spores that replace the wheat grains.

14. Karnal Bunt is a disease of: [U.P. R.O./A.R.O. (Pre) 2016]

Correct Answer: (b) Wheat crop
Solution:

Karnal bunt is also called a partial bunt. It is caused by the fungus Tilletia indica which infects grains at flowering. It reduces grain quality through the production of masses of powdery spores that discolor the grain and grain products.

The name 'Karnal Bunt' comes from the city of Karnal in Haryana. The most susceptible hosts of the disease are-wheat, durum wheat, triticale.

Karnal bunt spreads mainly through the movement of infected grain. However, teliospores can be carried on machinery, trucks, animals, and anything that disturbs and moves the soil.

Since only a few grains in each wheat head are infected, it is easiest to detect symptoms after the grain has been harvested.

15. Tungro virus of rice is spread by: [U.P.P.C.S. (Mains) 2009]

Correct Answer: (d) Green leafhoppers
Solution:Tungro virus affects rice and is transmitted by green leafhoppers. It involves two viruses: RTSV (Rice Tungro Spherical Virus) and RTBV (Rice Tungro Bacilliform Virus).

Infected plants exhibit stunting, reduced tillering, and yellow or orange-yellow leaves. Panicles may be small, not fully exerted, and many grains are sterile or partially filled. Infected plants early in the growing season may be killed.

16. Consider the following: [I.A.S. (Pre) 2018]

1. Birds

2. Dust blowing

3. Rain

4. Wind blowing

Which of the above spread plant diseases?

Correct Answer: (d) 1, 2, 3, and 4
Solution:Plant Pathology (also Phytopathology) is the scientific study of plant diseases caused by pathogens and environmental conditions (physiological factors). These factors include wind, rain, animals, soil, nursery graft, contaminated equipment and tools, infected seed stock, pollen, dust storm, irrigation water, birds and humans.

17. What causes ‘Blackheart’ in potato? [U.P.P.C.S. (Spl.) (Pre) 2008]

Correct Answer: (c) Oxygen deficiency
Solution:Blackheart is an abiotic disease which is caused due to low availability of oxygen during storage of potato. During storage, if tubers are not properly ventilated or stored in airtight conditions, oxygen levels can drop, leading to the development of blackheart.

High temperatures, especially in conjunction with low oxygen, can exacerbate the problem. Blackheart manifests as dark, often black discoloration within the tuber, particularly in the center. The affected tissue remains firm and may be irregular in shape.

18. Yellow vein mosaic disease in okra, caused by: [U.P.P.C.S. (Mains) 2002]

Correct Answer: (b) Whitefly
Solution:Yellow vein mosaic disease in okra is a viral disease. Whitefly is a factor of this virus.

19. ‘Yellow Vein Mosaic’ is a serious disease of: [U.P.P.C.S. (Mains) 2016]

Correct Answer: (b) Okra
Solution:Yellow vein mosaic disease in okra is a viral disease. Whitefly is a factor of this virus. OYVMD is caused by a virus, specifically the Okra Yellow Vein Mosaic Virus (OYVMV). The virus is primarily transmitted by whiteflies (Bemisia tabaci), which are insects that feed on the phloem sap of plants.

Whiteflies acquire the virus from infected plants while feeding and then transmit it to healthy plants during subsequent feeding. Infected okra plants exhibit symptoms like chlorosis (yellowing of leaves), stunted growth, and reduced yield.

20. ‘Spongy Tissue’ is a serious disorder hampering the export of mango variety. It is: [U.P.P.C.S. (Mains) 2002]

Correct Answer: (a) Alphonso
Solution:

Spongy tissue disorder, characterized by white corky tissue or internal breakdown, is peculiar to Alphonso mangoes in South India. Studies have indicated that high temperatures and the transfer of heat from the environment to the fruit can contribute to the development of spongy tissue.

During fruit growth, competition between developing fruits for nutrients and resources can also play a role. Some research suggests that deficiencies in certain minerals, like calcium and boron, may also be involved in the development of spongy tissue.