Crown gall is a disease of plants caused by the bacterium Agrobacterium tumefaciens that affects over 1000 plant species. Symptoms include round, rough galls forming at or near the soil line on infected plants. The disease is transmitted when the bacterium enters through wounds in the plant and induces tumor formation through genes carried by its Ti plasmid. The Ti plasmid integrates a segment called T-DNA into the plant's chromosomes that directs the plant to produce compounds the bacteria uses as nutrients, genetically engineering the infected plant cell.

2. Crown gall, disease of plants caused by Agrobacterium
tumefaciens
1000’s of plant species are susceptible; they include
especially rose, nut trees, grape, many shrubs and
vines and perennial garden plants
Symptoms: roundish, rough-surfaced galls, several
inches or more in diameter, usually at or near the soil
line, or on roots and lower stems
The galls, at first cream coloured or greenish, later
turn brown or black.

3. Avoiding replanting for that period; removing
severely infected plants (including as many roots as
possible); protecting against injury; keeping down
weeds; controlling root-chewing insects and
nematodes; cutting away large galls on trees, and
disinfecting the wounds

4. It induces crown gall disease
Gram negative rods
Enters easily through plant wounds
Also forms tumour
Soil bacterium
Although no naturally occuring plasmids are known
in higher plants, one bacterial plasmid, the Ti plasmid
of A. tumefaciens is of great importance
Also referred as nature’s smallest genetic engineer

6. The ability to cause crown gall disease is associated
with the presence of the Ti (tumor
inducing) plasmid within the bacterial cell. This
is a large (greater than 200 kb) plasmid
that carries numerous genes involved in the infective
process
The ability to cause crown gall disease is associated
with the presence of the Ti plasmid within the
bacterial cell.
This is a large (greater than 200 kb) plasmid

7. That carries numerous genes involved in the infective
process

8. A remarkable feature of the Ti plasmid is that, after
infection, part of the molecule is integrated into the
plant chromosomal DNA
This segment, called the T-DNA, is between 15 and 30
kb in size, depending on the strain.
It is maintained in a stable form in the plant cell and
is passed on to daughter cells as an integral part of the
chromosomes

9. But the most remarkable feature of the Ti plasmid is
that the T-DNA contains eight or so genes that are
expressed in the plant cell and are responsible for the
cancerous properties of the transformed cells.
These genes also direct synthesis of unusual
compounds, called opines, that the bacteria use as
nutrients.
In short, A. tumefaciens genetically engineers the plant
cell for its own purposes