This set of Virology Multiple Choice Questions & Answers (MCQs) focuses on “Transmission of Plant Viruses”.
1. How do viruses move from one cell to another cell after infecting a plant?
a) Through chloroplast
b) Through mitochondria
c) Through nucleus
d) Through plasmodesmata
View Answer
Explanation: When a virus infects a plant, it moves from one cell to another and multiplies in most of the cells. Viruses move from one cell to another through the plasmodesmata connecting adjacent cells. In leaf parenchyma cells the virus moves approximately 1 millimeter, or 8 to 10 cells, per day.
2. How do long distance transport of viruses take place through the plant system?
a) Through phloem
b) Through chloroplast
c) Through vacuole
d) Through nucleus
View Answer
Explanation: During viral infections, the viruses reach the phloem. Then the viruses are transported over long distances through the phloem. After entering the phloem, the virus moves towards the growing regions or food utilizing regions of the plant. Then the virus spreads systemically throughout the plant, and reenters the parenchyma cells which are adjacent to the phloem through plasmodesmata.
3. Which of the following plant viruses is transmitted through pollen?
a) Peach mosaic virus
b) Tobacco mosaic virus
c) Prunus necrotic ring spot virus
d) Potato virus X
View Answer
Explanation: Plant-to-plant transmission of virus through pollen occurs in sour cherry infected with Prunus necrotic ring spot virus. Virus transmitted by pollen causes reduced fruit set. It may infect the seed and the seedling that will grow from the infected fruit, and can spread through the fertilized flower to the mother plant, which thus becomes infected with the virus.
4. Which of the following mite families can transmit viruses?
a) Eriophyidae
b) Carabodidae
c) Sarcoptidae
d) Demodecidae
View Answer
Explanation: Mites of the family Eriophyidae can transmit at least six viruses, including Wheat streak mosaic virus and several other Rymoviruses affecting cereals. These mites have piercing and sucking mouth parts. Virus transmission by Eriophyid mites is very specific, because each of these mites is the only known vector for the virus or viruses it transmits.
5. Which of the following fungi can transmit viruses?
a) Agaricus
b) Olpidium
c) Amanita
d) Boletus
View Answer
Explanation: Root-infecting fungus Olpidium, which belongs to the class Chytridiomycetes can transmit about 30 different plant viruses. The fungi can infect new host plants with the viruses. Some of these viruses are carried internally, while others are carried externally on the resting spores and the zoospores of the fungi.
6. Which of the following plants can transmit viruses from one plant to another?
a) Rose
b) Hibiscus
c) Dodder
d) Lavender
View Answer
Explanation: Dodder is a parasitic plant which can transmit viruses. The twining stems of dodder can form a bridge between two plants. The viruses are transmitted from one plant to another through the bridge. The virus is transferred from the infected plant to the healthy plant through the phloem tissue of the dodder plant.
7. Tobacco mosaic virus can spread naturally from one plant to another by mechanical transmission of sap.
a) True
b) False
View Answer
Explanation: Tobacco mosaic virus is easily transmitted mechanically, and in nature it spreads by incidental contact and wounding. In this process direct transfer of sap occurs through contact of one plant with another. Such transmission takes place after a strong wind injures the leaves of adjacent diseased and healthy plants or when plants are wounded, and the sap carrying virus is transferred to wounded plants.
8. Which of the following is the process of transmission of Bean common mosaic virus?
a) Seed transmission
b) Sap transmission
c) Fungus transmission
d) Mite transmission
View Answer
Explanation: Bean seeds can transmit Bean common mosaic virus. More than 80% of the seeds produced from the virus infected mother plant, can produce new plants infected with the virus. The crops of bean fields are infected with Bean common mosaic virus in the early growing season due to seed transmission. The infection causes economic loss.
9. The viruses taken up and retained by the insect tissues are known as persistent viruses.
a) True
b) False
View Answer
Explanation: The viruses which accumulate inside the internal organs of insect vectors and infect the plants through the mouthparts of the insects are known as persistent viruses. Some persistent viruses may multiply in their respective vectors and those are called propagative viruses. Persistent viruses invade the salivary glands of their insect vectors.
10. Which of the following transmits Lettuce infectious yellows virus?
a) Cockroach
b) Whitefly
c) Butterfly
d) Roundworm
View Answer
Explanation: Lettuce infectious yellows virus is transmitted by the sweet potato whitefly. Whiteflies acquire the virus after feeding for 10 minutes or more, but their efficiency increases with feeding durations up to one hour or longer. Whiteflies carrying the viruses can infect healthy plants for up to three days after feeding on an infected plant.
11. Which of the following vectors can transmit rice tungro spherical virus?
a) Aphids
b) Leafhoppers
c) Nematodes
d) Mites
View Answer
Explanation: Rice tungro spherical virus is transmitted by several species of leafhoppers. It is a single stranded RNA virus which causes the Tungro disease of rice. The virus is transmitted in a semipersistent manner which means the insects can transmit the virus after fairly long feeding periods of several minutes to several hours.
12. Which of the following insects acts as a vector of plant viruses?
a) Bee
b) Butterfly
c) Aphid
d) Spider
View Answer
Explanation: Aphids have piercing and sucking mouthparts. They feed on the infected plants and carry the viruses on their stylets. Thus, they can act as vectors and infect the healthy plants. The viruses carried by insects with sucking mouthparts are known as stylet-borne viruses.
13. Which organism can transmit tobacco rattle virus?
a) Nematodes
b) Bacteria
c) Fungi
d) Insect
View Answer
Explanation: Tobacco rattle virus is transmitted by nematodes. Nematode vectors transmit viruses by feeding on roots of infected plants and then eating roots of healthy plants. The virus can remain in the vector for many weeks but does not multiply in the vector.
14. Which type of diseases are caused by vector transmitted viruses?
a) Monocyclic
b) Sporadic
c) Polycyclic
d) Endemic
View Answer
Explanation: Polycyclic diseases are caused by vector-transmitted viruses. The number of disease cycles per season varies from a few (2–5 for nematode-transmitted viruses) to many (10–20 or more for aphid-transmitted viruses). Vector mediated transmission of virus not only bring the virus into a crop (primary infection), but also result in transmission of the virus from infected to healthy plants within the same plant generation and during the same growth season (secondary infections). So, vector transmitted diseases are polycyclic.
15. Which of the following methods is used in laboratory to transmit viruses for experimental purposes?
a) Mechanical transmission through sap
b) Seed transmission
c) Pollen transmission
d) Insect transmission
View Answer
Explanation: Mechanical transmission of viruses through sap is performed in laboratories to study the viruses that cause plant diseases. For mechanical transmission of a virus, infected young leaves and flower petals are ground to crush the cells and the virus is released in the sap. The healthy plants are inoculated by rubbing the sap gently on the leaves.
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