Report on the Agricultural Experiment Stations, 1952 Page: 52
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52 REPORT ON EXPERIMENT STATIONS, 1952
the electron microscope and its wider use at the State experiment stations
has done much to facilitate research in the plant viruses. The
use of radioactive isotopes has stimulated more penetrating study of
cell behavior and other phenomena of plant growth related to disease.
A new line of research receiving considerable emphasis is the development
of systemic fungicides or chemotherapeutants. Although research
with these compounds is encouraging, it is too early for many
stations to report conclusive results. The significance and highly
scientific nature of plant disease research, and its contribution to agricultural
production, is reflected in the several examples of numerous
station accomplishments reported in the past year.
Plant Viruses
Some viruses have a wide host range. These hosts include many of
our economically important plants. Viruses are transmitted from
plant to plant by insects and in many other ways. It is, therefore, important
to know about the life history of the viruses and to understand
how they may be spread, in order to adopt necessary control measures
when the plants and crops get sick.
The California station has isolated seven viruses believed to be
separate and distinct. They were taken from plants in the cucumber
family growing in the State. The mosaic viruses are the aphid-borne
cucumber, cantaloup, and western watermelon; the beetle-transmitted
squash, muskmelon, and wild cucumber viruses; and the virus causing
muskmelon vein necrosis, which has been transmitted by juice inoculation.
The insect vectors for the latter have not yet been determined.
Antibiotic Studies
The organisms that cause certain diseases are becoming adjusted
to antibiotics such as penicillin, streptomycin, and others; that is, they
can tolerate heavier dosages of these materials. The reason for this
change has not been completely understood. The Wisconsin station
found that bacterial cultures which had never been exposed to antibiotics
contained a small number of resistant cells. After treatment
with antibiotics, these cells became more numerous because the susceptible
cells had been killed. Eventually, these resistant cells dominated
the culture and the disease caused by these organisms resisted treatment
by antibiotics.
The New Jersey station investigated several new antibiotic-producing
cultures in detail. One was found to produce an active antifungal
agent which, although similar in most respects to fungicidin,
has a marked activity against Coccidioides. Another culture was
found to produce antibacterial and antifungal agents that were found
to be identical with terramycin and rimocidin. A new antifungal
agent was isolated that was. particularly effective against Candida
albicans, a yeast-like fungus that may cause serious lesions on many
parts of the human body. This antibiotic was recently designated as
candicidin. Further studies were carried out on the nutrition of
Streptomyces fradiae and on the mechanism of formation of neomycin
by this organism. A number of cultures were isolated that presented
a marked action against the tuberculosis organism.
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1952, book, January 1953; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc5990/m1/54/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.