Biology Reference
In-Depth Information
Bacterial Diseases
Rhizobiaceae
spherical protuberances or elongated ridges of
white gall tissue, turning brown after several
weeks. Canes often split open and dry out; pro-
duce small seedy berries. Cane gall is not as
important as crown gall, but one should use the
same preventive measures. Avoid runner plants
from infected mother plants.
Agrobacterium tumefaciens
Crown Gall
on
a great variety of plants in more than 40 families,
general on blackberry, raspberry, and other bram-
bles, on grapes and on rose (see
Fig. 1
); on fruit
trees - apple, apricot, cherry, fig, peach and nec-
tarine, pear (rarely), plum; on nuts - almond very
susceptible, walnut fairly susceptible, pecan
occasionally; on shade trees, willow and other
hard woods; rare on conifers but reported on
incense cedar and juniper; on many shrubs and
vines, particularly honeysuckle and euonymus;
on perennials such as asters, daisies, and chrysan-
themums; and on beets, turnips, and a few other
vegetables, with tomato widely used in experi-
ments. Crown gall was first noticed on grape in
Europe in 1853, and the organism was first iso-
lated in 1904 in the United States from galls on
Paris daisy. It is of first importance as a disease of
nursery stock, but may cause losses of large pro-
ductive trees in neglected orchards, especially
almonds and peaches in California and other
warm climates. It is very important to rose
growers and to the amateur gardeners who some-
times receive infected bushes.
Symptoms
The galls are usually rounded, with an
irregular rough surface, ranging up to several
inches, usually occurring near
Agrobacterium
Small, motile, short rods, with two to six peritri-
chous flagella or a polar or subpolar flagellum,
ordinarily Gram-negative, not producing visible
gas or detectable acid in ordinary culture media;
growth on carbohydrate media usually accompa-
nied by copious entracellular, polysaccharide
slime; gelatin liquefied slowly or not at all; opti-
mum temperatures 25
to 30
C. Found in soil, or
plant roots in soil, or in hypertrophies or galls on
roots or stems of plants.
Agrobacterium rhizogenes
Hairy Root
of
apple, also recorded on cotoneaster, hollyhock,
honey locust, honeysuckle, mulberry, peavine,
peach, quince, Russian olive, rose, and spirea.
“Woolly root” and “woolly knot” are other
names given to this disease, which was long
considered merely a form of crown gall. Both
diseases may appear on the same plant and in
early stages be confused. In hairy root a great
number of small roots protrude either directly
from stems or roots or from localized hard swell-
ings that frequently occur at the graft union. The
disease is common on grafted nursery apple trees
1, 2, or 3 years old, and the root development may
be as profuse as witches' broom. Control mea-
sures are the same as for crown gall.
Agrobacterium rubi
Cane Gall
of brambles, on
blackberry, black and purple raspberries, and,
very rarely, red raspberry. Symptoms appear on
fruiting canes in late May or June as small,
the soil
line,
