EPWS 310 - Plant Pathology
Lectures - Fall 2002
Readings – Chapter 1
I.
History of Plant Pathology
Earliest recorded
history is found in Genesis. Blight, blast, and mildew were induced by fungi.
The Greek
philosopher Theophrastus (370-286
B. C.) was the first to write about diseases of trees, cereals, and legumes.
The Romans had
infections of rust on their wheat. They blamed the disease the gods Robigo and
Robigus. They appeased the god with a religious ceremony, the Robigalia, which
was observed for over 1,700 years. The ceremony involved sacrificing red (rust
colored ) animals such as dogs and cows.
In 1660, Anton
Van Leeuwenhoek (1632-1723)(a
janitor), first saw bacteria. He made 247 different microscopes that could
enlarge objects 40 to 270 times.
Also in 1660,
farmers in France got legislation passed to eradicate barberry, because they
had noticed that rust was worse in plants near barberry bushes.
In 1729, Micheli
described the spores of Rhizopus (a common bread mold). He thought that the spores were
the fungal seeds and that these seeds were carried through the air.
In 1755 Tillet added black dusts from wheat to seeds and kept some
seed clean. He observed that the seed that had the bunt or stinking smut dust
had more disease.
From the middle
ages through the mid-1800's, a disease known as St. Anthony's fire frequently
affected peasants which ate a fungal toxin produced on grain.
In 1807, Prevost
proved that bunt is the cause of bunt
of wheat. Unfortunately, few believed him.
II. The beginning of Plant Pathology
1845.
Irish Potato Famine. Susceptible host?
Conducive environmental factors?
Virulent pathogen?
Dr. C. Montagne, first described the fungus found on the potatoes. Rev.
M. J. Berkeley, recognized that this
new fungus was connected with the blight. Dr. John Lindley, a botany professor at University College in London,
who did not believe that the fungus was the cause of the blight.
Anton De Bary, the father of Plant Pathology, performed the
experiments that proved the role of the fungus in the blight. The notion of
causality established the science of plant pathology.
In 1860, Louis Pasteur disproved the dogma of Spontaneous Generation (which
was ???). This theory was replaced by the germ theory in which it was finally
recognized that microbes induced disease.
II. The first fungicide.
In 1880, downy
mildew (Plasmopara viticola)
caused an epidemic on grapes in France. Alexis Millardet recognized the first fungicide, Bordeaux mixture. Bordeaux mixture is effective against many fungi and
bacteria, is inexpensive, and is the most widely used fungicide in the world.
III. How to prove pathogenicity: Koch's
postulates
Robert Koch, a
German microbiologist, who worked on anthrax of sheep developed a method to
prove pathogenicity.
Koch's postulates:
1.
The symptoms and signs of the pathogen in the diseased host are described.
2.
3.
4.
IV. History of other plant pathogens
In 1878, Thomas
Burrill, an American Plant
Pathologist, implicated a bacterium as the disease agent of the fire blight
disease in North America that was causing the death of apple and, especially,
pear trees. Another American plant bacteriologist, Erwin F. Smith, contributed greatly to our understanding of
bacteria.
In 1892, a Russian
scientist named D. Ivanoski, first
showed that viruses could cause disease. He worked with TMV (Tobacco mosaic
virus). Controversy with A. Mayer. a German scientist who thought it was a
bacteria.