EPWS 310 - Plant Pathology

Lectures - Fall 2002

 


Lecture 2

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.

 

 

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