Plant Science and Cancer

The work of Erwin F. Smith illustrates our conviction that agricultural research is a relative and component of all science. Of all the giants among Department research men, it would be hard to find one who has influenced more fellow scientists or contributed more to his chosen branch of science than he. Professor Burrill, of Illinois, had demonstrated that bacteria could cause diseases in plants, but it remained for Smith to prove this truth to the world.

He came to work for the Department in 1886, just 8 years after Bur-rill's famous work. Smith's first years were spent working on peach yellows. He proved that the current ideas as to its cause were wrong; that it could be held in check by systematically destroying all affected trees. His evidence was accepted by the growers, who united their efforts for compulsory eradication programs, and the peach industry was saved. He concluded that the techniques available at the time were inadequate to show the cause of this disease and turned his attention to bacterial and fungus diseases. He investigated, and described for the first time, many kinds of bacteria that caused destructive plant diseases and determined how they cause such diseases as well as what plants were susceptible. Besides numerous bulletins and other scientific papers, he published three quarto volumes in which he gave the methods he had found most useful and a monographic treatment of the diseases on which he had worked most.

Despite the high caliber of the work done by Burrill, Waite, and Smith, leading bacteriologists of Europe, particularly of Germany and England, were not convinced that bacteria could cause diseases in plants. In fact, one of these men, Dr. Alfred Fischer, of Germany, a prominent writer of textbooks, became the spokesman for the doubters, and Erwin Smith took up the fight for the Americans. The debate went on for years in one of the leading German scientific publications. It was bitter at times, but Smith finally won the decision and, with it, fame. He carried on countless experiments to provide evidence for his international debate. It was in this connection that he and two of his assistants, C. O. Townsend and Nellie Brown, discovered that certain plant tumors are caused by bacteria. This discovery led to another great contribution by Smith, which was destined to bring him more lasting and widespread recognition perhaps than all his other scientific work combined—his studies on the bacterial crown gall of plants.

The first two papers—published with Townsend in both English and German—described and named the bacterial cause. Then followed in rapid succession the long series of papers dealing with many phases of the development of plant tumors, bringing the grand total on this subject to some 40 or more. His intensive comparative researches on these malignant growths in plant and animal tissues won him wide attention among cancer specialists. In 1913 the American Medical Association awarded him its certificate of honor for his work on cancer in plants and in 1925, only a little over a year before his death, he was elected president of the American Association for Cancer Research—signal honors for a man engaged in plant research, and evidence of the kinship of the sciences.

About the time that Erwin F. Smith was devoting his attention to the wilt diseases, a young man named William A. Orton came to work for the Department. He was from Vermont and was trained in plant pathology. His first assignment was to investigate the wilt disease of cotton, a disease that lives over from year to year in the soil. Young Orton had never seen a field of cotton. The disease was spreading at an alarming rate when he made his first visit to the islands off the coast of South Carolina in 1899. He found a grower there named Rivers who had been selecting seed from occasional plants that showed resistance to the wilt. Orton encouraged Rivers to continue the work and helped him make selections. By this time the disease was also threatening the main Cotton Belt of the South, so Orton laid out experimental breeding plots and went to work to breed a new kind of cotton. This was the beginning of the breeding of plants for resistance to disease. The trial plots were in Dillon County, S. C., and the first new cotton variety to come from these plots was named Dillon.

Orton's work was a landmark in farm research. To me, it shows another aspect of our tradition, that of seeing a need and bending every effort to fill it. A similar landmark is the work of Dr. E. C. Stakman, of the University of Minnesota. In 1913 he reported work which established the existence of strains or races of disease-causing organisms. He confirmed earlier work done in Sweden indicating that stem rust on wheat differed from stem rust on oats or rye.

He went further and showed that stem rust on wheat or oats is not produced by a single organism, as previously believed. Instead, he found that several closely related organisms could produce stem rust. These he called pathogenic races. This opened up a new approach in the understanding and control of many plant diseases. It explained why a new variety of wheat, for instance, bred for resistance to one form of stem rust may look promising for a few years, only to succumb to another form of stem rust. Apparently the form that caused the trouble originally was the one best adapted to the environment. When a new variety of wheat resistant to this form is introduced, the dominant race becomes subordinate and is no longer a serious factor in crop production. However—and this is why plant breeders cannot quit when they develop a new disease-resistant variety—still another race of the disease organism may, and usually does, quickly increase its numbers because the new variety is not resistant to all races.