Report on the Agricultural Experiment Stations, 1953 Page: 94
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94 REPORT ON EXPERIMENT STATIONS, 1953
kill the organisms while others do not; how do the multitudes of
viruses, bacteria, and fungi affect plant cells; why are some destructive
and others harmless ? To conduct fundamental research of this
nature requires well-trained scientists. The science of plant pathology
as carried on at State agricultural experiment stations provides
excellent opportunities for sound research as is revealed by the subsequent
examples of recently reported research.
Disease Resistance in Plants
Studies at the Wisconsin station on the nature of fusarium wilt
in tomato have shown that the disease is initiated by the enzyme, pectinase,
produced by the fungus that caused the plants to wilt and sap
vessels to turn brown. Pectinase is the enzyme that breaks pectin cell
wall materials into sugar within the plant. The resistant character
was shown to be distributed throughout the plant and not confined
to the root system as earlier studies indicated. Why one plant is
resistant and another susceptible is still unknown, but as facts are
gradually uncovered, an answer will be forthcoming.
In seeking the reasons why some potatoes are susceptible and others
resistant to the ring rot bacterium, the North Dakota station found
that the susceptible Triumph potato stem was comparatively rich in
the amino acid proline, but contained only traces of asparagine. The
opposite was true for the highly resistant plants. In addition to
these significant differences, the resistant plant had a greater concentration
of the amino acids. If a plant's resistance to a disease organism
can be explained on this basis, the development of resistant varieties
may be facilitated.
The difference between scab-resistant and scab-susceptible potatoes
is only skin deep, according to recent research at the Wisconsin station.
Some outside cells of the skin die as a potato gets bigger. These
cells are shed from the skin of resistant varieties, but cling to the
surface of susceptible varieties. When the dead skin gets several
layers thick and breaks up into irregular masses, the scab organism
evidently finds a home. This research has yielded what may be an
easier way to test seedlings for scab resistance. A quick and simple
microscopic test would take the place of a generation of potatoes
grown in the greenhouse and selected for scab resistance. In this connection,
the Colorado station (coop. USDA) found that the amount of
chlorogenic acid present in the skin of the potato tuber determines its
resistance to the scab fungus Streptomyces scabies. Tubers from a
highly scab resistant potato seedling contained 77 mg. of chlorogenic
acid per 100 grams of peelings, whereas, a susceptible seedling contained
only 40 mg. chlorogenic acid per 100 grams of peelings.
Diseases of Field Crops
Yellow-dwarf, a comparatively new and damaging virus disease of
cereals, occurred over wide areas in California in 1951. The disease
causes leaf yellowing in barley, leaf reddening and head blasting in
oats, and a chlorosis in wheat. Moderate to severe stunting occurs in
all three cereals. The California station has shown that the disease
is caused by a virus and that it is readily transmitted by five species
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1953, book, 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5989/m1/96/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.