Viruses

Question 1

Name 2 Plant viruses

Answer 1

Tobacco Mosaic

Potato Leaf curl virus

Question 2

Describe damage done by tobacco mosaic virus

Answer 2

Stunted growth and reduced yield
Mosaic pattern in lighter green/brown on mature leaves.
Young leaves curl downwards and become bronzed
Fruit ripen unevenly with pale patches and marbling

Question 3

How is Tobacco mosaic virus spread

Answer 3

Rely on vectors to transmit e.g. Fingers of gardeners or tools
Enters plant leaves through microscopic wounds such as broken leaf hairs or de leafed side shoots.
Occasionally transmitted through seed.

Question 4

Name 2 methods of minimising the effect of Tobacco Mosic virus

Answer 4

Remove and destroy infected plants promptly.
Hygiene is of great importance. Do not touch anything else after handling and disinfect and sterilise any tools with Virkon S.
Wash hands.
Grow bags will avoid soil infection from a previous crop
Purchase resistant variety e.g ‘Cherry Wonder’

Question 5

Describe the symptoms of Potato Leaf Roll Virus

Answer 5

Rolling upwards of leaves (may turn red on upper and purple on lower side)
Stiffness and leathery leaves
Reduction in potato yield

Question 6

Describe 2 different methods of minimising potato leaf roll virus.

Answer 6

Buy certified seed potatoes and best to buy resistant cultivars such as Valor
Spray with and insecticide - Deltamethrin

Question 7

Life cycle of Potato Leaf Roll Virus

Answer 7

Carried in the mid gut of aphid
Injected into phloem of potato plant when aphid feeds via injected saliva. 10-20 minutes is needed for transfer.
Insect may remain infected with virus for whole growing period of crop.