Question

Crown gall in plants is caused by which of the following bacterium?
A) E. coli
B) Erwinia
C) Agrobacterium
D) Pseudomonas

Answer 1

Hint: Bacteria are the prokaryotic organisms which cause disease to both plants and animals. Crown gall is a disease in plants is caused by the bacterial plasmid which causes the formation of tumour-like outgrowth in the junction of roots and shoot in the plants. Crown gall is caused by the bacteria which is used as an important tool in genetic engineering.

Complete answer:
Crown gall is a disease in plants which is caused by Ti plasmid. The causative agent of the gall crown agent is capable of transferring its DNA to the plants as a result of which it is used as an important tool in biotechnology. The Ti plasmid is present in the Agrobacterium tumefaciens in which the conjugative DNA transfer takes place between the bacterium and the plant. The plasmid is incorporated into the genome of the plant and leads to the formation of tumours.

E. coli- E. coli is a gram-negative facultative anaerobe which is present in the gut of humans. It causes several diseases in animals/humans like food poisoning.

Erwinia- It is a gram-negative facultative anaerobe. It causes fire blight in the Rosaceae family like pears and apples. It is a serious disease which can destroy an entire orchard.

Pseudomonas- It is a gram-negative bacterium which can live in several habitats including human skin. It causes diseases like severe lung infections in humans.

Thus, the correct answer is option ‘C’.

Note: Agrobacterium thrives in wet environments. So, keeping the crown of the tree dry or preventing deep planting into the soil can prevent the disease. The removal of the gall is an effective way for treatment of the disease. Rose, liliac are prone to this infection. The coniferous plants are inert to Agrobacterium.