Disease Forms - Plant Crown Gall

Question 1

What is Crown Gall Disease?

Answer 1

A disease caused by Agrobacterium Tumefaciens; found throughout Australia - dominant impact on roses and stone fruit in WA.

Question 2

What are the key symptoms of the disease?

Answer 2

Growth of tumours:

• based at the base of the trunk.
• interrupt normal water/nutrient flow - stunted growth - potentially killing the plant.

Question 3

How is the disease transmitted?

Answer 3

Direct Contact - root to root.

Indirect Contact - human activity shifting soils (tyres, boots, etc.).

Question 4

Outline its lifecycle.

Answer 4

• Plant is injured - portal of entry.
• Inside the plant root, the bacterium reproduces quickly via. binary fission; forming the tumour.
• Made by integrating some of its DNA; contained in a circular plasmid, into the host’s DNA.
• Once bacterial DNA is incorporated into the host’s genome - uncontrolled cell division - tumour.
• The bacteria can replicate in soil from tumour sheddings - carried by rainwater.

Question 5

How can we control the spread?

Answer 5

• Using Crown Gall free soil.
• Removing infected plants from nursery’s.
• Minimise human impacts.

Question 6

What are the favoured conditions of disease spread?

Answer 6

Continous nursery plantings of susceptible species.

Management practices that cause root damage.