intro to plant viruses

Question 1

what is a virus?

Answer 1

• infectious units comprising RNA or DNA genomes enclosed in a protective coat
• their DNA codes for proteins necessary for replication but they contain no energy-producing enzyme systems
• the host cell may or may not be destroyed in process of viral replication n release
• obligate parasites

Question 2

what is the size range of viruses?

Answer 2

from <20nm to > 1000nm

Question 3

describe the structure of a virus

Answer 3

nucleic acid protected by coat protein (capsid)
proteins can assemble into icosahedral shape, using 3 diff proteins

Question 4

what are viroids?

Answer 4

• smallest known pathogens
  -> single-stranded RNA pathogens
  -> no proteins
• highly stable due to complex structure

Question 5

what is the nomenclature of viruses determined by?

Answer 5

first host they are found in + dominant symptom in that host

Question 6

what are the 4 taxonomic levels in virology?

Answer 6

1. family
2. genus
3. species
4. strain

Question 7

what are classic symptoms associated with viruses?

Answer 7

• chlorosis: loss of green coloration of leaves caused by iron deficiency
  -> chlorotic streaks, spots, veining, mosaic, interveinal chlorosis, leaf curl chlorosis
• necrosis
  -> vein necrosis, necrotic spots
• dwarfing/stunting
• marbling

Question 8

in what ways can viruses be good?

Answer 8

• cold tolerance
• drought tolerance
• better taste, eg jersey potatoes made sweeter
• ornamental plants w patterns caused by viruses