Question

Potato leaf roll or curl of papaya are caused by
A. Fungi
B. Viruses
C. Bacteria
D. Nematodes.

Answer 1

Hint: This disease is carried by green peach aphid which is the primary vector for the microorganism causing potato leaf roll or curl of papaya. In warm humid conditions chances of infections are higher.

Complete answer:
Potato leaf roll or curl of papaya are diseases in which leaf of the potato become chlorotic and sometimes purple discoloration. Some plants may encounter phloem tissues necrosis. Some plants produce smaller tubers and stunted growth.
The microorganism responsible for this disease is Potato leafroll virus (PLRV). This PLRV is a member of the genus Polerovirus. It is a positive sense RNA virus which infects potato, papaya and other members of family Solanaceae.
PLRV is introduced to its host plants by planting infected seeds or by its insect vector that is green peach aphid. Aphids acquire these viruses from infected plants and infected phloem are taken up by aphid style to the digestive system of aphid. Then the virus crosses the membrane of the gut and enters into the salivary gland.
After this aphid continues to transmit the virus throughout its life.

Thus, we can conclude that Potato leaf roll or curl of papaya are caused by viruses. SO, option ‘B’ is the correct option.

Note: PLRV requires a humid condition for the successful transmission of the virus and infection to the host plant. This infection produces potatoes which are not acceptable in the market which cause huge loss in the productivity of the crop. This can be prevented by insecticides and by reducing the population of aphids.