MORPHOGENESIS OF CROWN
GALL
47
(1961) have given a list of plants susceptible to the strain B-23: according to this 32 of the 76 dicots investigated formed tumors. One of the
strains most widely used for experimental purposes is B 6 . It was originally
isolated by Braun, and it is highly virulent on a number of dicotyledonous
plants. Other strains are also continuously maintained in different laboratories. Kalanchoe
daigremontiana
and Datura stramonium
may be
mentioned as two of the most often used experimental plants.
Attempts to induce the crown gall disease in monocots have generally
failed. The reason is unknown and presents a problem of interest. Tumors
somewhat resembling crown gall are common in coniferous trees and
have been dealt with in a number of papers (e.g., White, 1957; White
and Millington, 1954a,b).
The crown gall organism has been the subject of a great number of
studies. For example, Beaud (1965) has published an extensive investigation on the biochemical characteristics of Agrobacterium
tumefaciens.
He has also reviewed a number of the earlier studies. Recently, Beardsley
and Lipetz (1966) have investigated the effect of 5-fluorouracil and
5-fluorodeoxyuridine, and Heberlein and Lippincott (1965) the effect
of ultraviolet light on the bacteria. Infectivity of certain mutants has
been studied by B. B. Lippincott and J. A. Lippincott (1966), and the
significance of spheroplasts for pathogenicity by Beardsley et al. (1966).
Certain properties of a number of bacterial strains have been discussed
by Beaud and Manigault (1966) and Bonnet (1966). The purpose of
most of these studies has been to solve the nature of the bacterial effect
in tumor induction, so far, however, without success.
III. Cell Conditioning and Tumor Induction
A. Conditioning
It has been known from the earliest experiments on crown gall that
wounding is essential for tumor formation. All attempts to induce
primary tumors without a wound have failed. For example, Rack (1954)
used vacuum to force bacteria, suspended in water or in wound sap, into
the intercellular spaces of certain succulent leaves. No tumors developed
in the unwounded leaves. However, wounding the bacteria-containing
leaves with a sterile needle gave rise to numerous tumors. The manner
of wounding does not seem to be important. In laboratory experiments
the wounds have often been caused by a needle, recently also by rubbing
with Carborundum (Lippincott and Heberlein, 1965). In nature freezing
and thawing leads to wounding especially in the crown of the plants,
GALL
47
(1961) have given a list of plants susceptible to the strain B-23: according to this 32 of the 76 dicots investigated formed tumors. One of the
strains most widely used for experimental purposes is B 6 . It was originally
isolated by Braun, and it is highly virulent on a number of dicotyledonous
plants. Other strains are also continuously maintained in different laboratories. Kalanchoe
daigremontiana
and Datura stramonium
may be
mentioned as two of the most often used experimental plants.
Attempts to induce the crown gall disease in monocots have generally
failed. The reason is unknown and presents a problem of interest. Tumors
somewhat resembling crown gall are common in coniferous trees and
have been dealt with in a number of papers (e.g., White, 1957; White
and Millington, 1954a,b).
The crown gall organism has been the subject of a great number of
studies. For example, Beaud (1965) has published an extensive investigation on the biochemical characteristics of Agrobacterium
tumefaciens.
He has also reviewed a number of the earlier studies. Recently, Beardsley
and Lipetz (1966) have investigated the effect of 5-fluorouracil and
5-fluorodeoxyuridine, and Heberlein and Lippincott (1965) the effect
of ultraviolet light on the bacteria. Infectivity of certain mutants has
been studied by B. B. Lippincott and J. A. Lippincott (1966), and the
significance of spheroplasts for pathogenicity by Beardsley et al. (1966).
Certain properties of a number of bacterial strains have been discussed
by Beaud and Manigault (1966) and Bonnet (1966). The purpose of
most of these studies has been to solve the nature of the bacterial effect
in tumor induction, so far, however, without success.
III. Cell Conditioning and Tumor Induction
A. Conditioning
It has been known from the earliest experiments on crown gall that
wounding is essential for tumor formation. All attempts to induce
primary tumors without a wound have failed. For example, Rack (1954)
used vacuum to force bacteria, suspended in water or in wound sap, into
the intercellular spaces of certain succulent leaves. No tumors developed
in the unwounded leaves. However, wounding the bacteria-containing
leaves with a sterile needle gave rise to numerous tumors. The manner
of wounding does not seem to be important. In laboratory experiments
the wounds have often been caused by a needle, recently also by rubbing
with Carborundum (Lippincott and Heberlein, 1965). In nature freezing
and thawing leads to wounding especially in the crown of the plants,