Plant Virology - Week 13 Flashcards
What is nucleic acid: Single stranded (ss) - positive sense RNA
This type is ready to function as a messenger RNA inside the host cell, therefore usasully infectous
What is nucleic acid:
Negative sense ssRNA
A negative-sense RNA has to be copied into a positive one before it can function. This is done by encoded enzymes found in the virus particles
What is nucleic acid:
Doulbe stranded dsRNA
Viruses with dsRNA also contain a viral encoded enzyme which copied the genomic RNA into mRNA
What is nucleic acid:
DNA virues
ds and ss use host enzymes to start the event
DNA can initiate this without them
What are viroids
unencapsidated, small, single stranded RNAs which replicate when inoculated into plants
Most plant virues are what type/s
ss+ve rna 75%
Plant virus symptoms
Local lesions - local area diseased tissue
(virus restricted to necrotic lesions and few layers of outer edge cell)
chlorosis - yellowing of leaves
mosaics - yellowing of leaves on green background
necrosis - tissue death, stress of specific virus
morphogenic disturbances - mess up plants
Economic impact of plant virues
reduction of plant size/ yeild and damaged fruit
Synergism (synergistic)
the association of two or more viruses acting at the same time
Layer plant virues have to break through
Cuticle, cellulose cell wall and epidermal cell
Main plant virus transmitters
Mainly insects / some fungi
White fly - transmit 70 serious disease agents
Aphids - 66% of invertebrate transmissions are aphids
Nematodes - Transport thru soil can last year, in air only hours
Fungi - Survive in dry soil for years, hours on surface
What is mechanical transmission?
Virus/ rna intor via wound on surface
TMV n PVX virues v successful with insects
Seed transmission?
1/5 of transmissions, viruses persist over long periods, infect by sexual
