Viruses General Flashcards
(16 cards)
Virys symptoms confused with
Herbicides Nutrient deficiencies and toxicities Genetic mutations of host Viroids Phytoplasmas ** alteration of metabolism and positive identification of virus difficult
Virus differences
Not spores or fruiting bodies like fungi
No bacterial ooze
Nor cultured
Virus diagnosis
Virus biology: symptoms,transmission
Virus paricles: e microscopy
Virus proteins: serology
Virus nucleic acids: molecular techniques
Plant virus diagnosis
Transmission
Symptoms
E microscopy
Serological and molecular tests to ID disease
Genetic mutation- chimera
Presence of one branch with very severe symptoms
Caused by somatic mutation at bud of branch
Examples of symptoms
Mosaic Mottle Vein banding and clearing Chlorotic and necrotic spots Rugosity Leaf rolling and curling Enations Leaf distortion Streaks Colour breaking Seed symptoms Fruit symptoms- mottling,spraining,stem pitting and grooving
Plant virus diagnosis
Other things needed
Distribution of virus in field
Evidence of spread
Rapidity of spread
Comparison with healthy plants
Disease transmission
Differentiate from abiotic- nutrient def,env stress,herbicide
Graft onto healthy indiv of same host
Simple budding
Twig diseased
Bud or bark patch
Healthy indicator with T shape cut or bark patch
Diseased bud/bark put in cut of indicator
New growth of indicator
Different methods virus detect
Leaf grafting
Approach grafting
Tissue implntation
Tuber core grafting
Graft- genetic compatible
Difficulties
Keep healthy and test plants apart
Weeks, monts- symptoms of recipient
Doesnt necessarily ID virus
Sink and source
Sink- where energy is needed
Aource- where energy is created
Mechanically transmissible
Enter through wound
Phloem limited is difficult
Virus size
30nm
Negative staining
Glow discharge TEM grid for hydrophilisation/hydrophobisation
Pipette plant sap on carbon support film- allow absorb
Touch edge with blotting paper to remove droplet
Dont dry completely- washing steps to remove salts
Pipette drop of staining solution- heavy metal salt
Air dry
Ultrathin sections
Ultramicrotome
