Diseases and pathogens Flashcards
What are the 3 broad classification of pathogens (based on their life cycle)?
- Necrotrophs
- Biotrophs
- Hemibiotrophs
What is a necrotroph?
Kills cells first then metabolises content.
What is a biotroph?
Invade living cells and subvert metabolism to favour growth.
What is a hemibiotroph?
Initially biotrophic, yet kills surrounding cells later on.
How does fungi infiltrate and infect plants?
- Through wounds
- Through natural openings such as stomata
- Through intact plant surfaces via enzymes that soften the cell wall.
How do you control a fungal infection?
Husbandry techniques - Crop rotation, Limit spread through quarantine and management practices
-use of tissue-cultured plants
-remove soil (spores) from machinery and footwear
Breeding - Requires sources of resistance.
Species must be fertile; many vegetatively propagated plants have low fertility eg. banana
Fungicides
Downsides:
Costly
Potentially harmful impact on humans and environment
Overuse may result in resistance
How do you control bacterial infection?
Quarantine
Disinfecting tools for pruning etc
Insecticides to help eliminate vectors of transfer
Breeding resistant plants
How do you identify a virus infection?
Electron microscopy
Molecular tests such as PCR
Serological tests such as immuno-strips
What are some symptoms of a viral infection?
Mosaics or mottling
Ring spots
Vein-clearing/yellowing
Streaking
Stunted growth
What are some of the pre-formed defences of plants?
Structural barriers:
- surfaces coated so that water runs off rather than remaining
- strong, rigid cell walls to reduce permeability even with enzymes to break down.
Antimicrobial chemicals
- can break down fungal cell walls
- inhibit enzymes used by pathogen to infect
- inhibits germination of known infected plant to reduce spread
What are some induced defences that plants have?
If pathogen recognised some plants can release cell wall reinforcements, can kill the cell/s hosting the pathogen to reduce spread.
Oxidative bursts can be applied to the area, which can kill the pathogen and the cells hosting.
How do plants recognise pathogens?
- Pattern recognition receptors (PRRs), recognise molecules characteristic or entire groups of pathogens using conserved biological ‘signatures’.
- Resistance (R) proteins, receptors that identify pathogen presence intracellularly
Describe a specific defense response plants have to viruses.
Notice a virus is present due to detection of long double-stranded RNA. Gene silencing can then be utilised. this degrades the viral sequences from the dsRNA and cleaves the areas containing.
