Crown Gall

Question 1

Is crown gall an infectious disease? Give reasons for your answer.

Answer 1

• yes
• caused by a pathogen/bacterium transmitted from one plant/host to another via water/soil
  strain of agrobacterium living in soil, transfer a segment of DNA (plasmid) to uninfected plant
  this causes Crown gall disease in new host plant

Question 2

symtoms of crown gall

Answer 2

galls from on stems, roots, trucks or branches, which can lead to stunted growth and wilting (because the gall formation interferes with water and good transport). initially gall form on the ‘crown’ of the plant, which refers to where the main roots join, just above soil level.

Question 3

Crown gall mode of transmission

Answer 3

Indirect soilborne spores via a root wound, or via a vehicle such as grafting or other gardening tools
Direct contact via infected root to wound on susceptible plant root.

Soilbourne
Can persist for years in soil + multiply in root zone of susceptible plants
Spread by movement of infested soil, infected plant material, budding + grafting tools

Question 4

Crown gall life cycle specifications

Answer 4

Entry via a wound of susceptible plant root
Replication in plant roots; bacteria transfer some plasmid DNA into the plant Genome; the inserted DNA codes for uncontrolled plant growth; plant cells grown and divide and form galls
Exit is via galls; through spores that drop into the soil or onto vehicles for further spread.

Question 5

crown gall pathogen name

Answer 5

Agrobacterium Tumefaciens

Question 6

crown gall symptoms

Answer 6

Galls form on crown of plant (where main roots join stem) and on roots
Small pale rough lumps of tissue  enlarge + darken
Sometimes no effect, otherwise severe infection
Stunted growth, may die if stressed by dry conditions

Question 7

crown gall evolutionary adaptations

Answer 7

Flagella
Allow it to swim through soil
Can insert own DNA into host (plasmid DNA)
Effective tool for plant breeding
Resistant
Produce own restriction enzyme that cuts tumour causing DNA
Produce proteins that insert into own cell membrane for uptake of tumour-produced substances

Question 8

management strategies - prevention

Answer 8

Do not use soil in which infection has occurred
Remove plants with suspicious swellings from area
Tools treated with disinfectant
Treating plants with biological control agent
Live culture of bacterium closely related to crown gall
Protects wound sites from infection

Question 9

management strategies - treatment

Answer 9

No cure
Best to destroy infected plants to try and limit spread to other plants