TSCHERMAK VON SEYSENEGG, ERICH

(b. Vienna, Austria, 12 November 1871; d Vienna, 11 October 1962)

botany, genetics.

Tschermak came from a family of scholars. His father, Gustav Tschermak, was director of the Imperial Mineralogical Museum and, from 1873, professor of mineralogy and petrography at the University of Vienna. He was created a member of the hereditary nobility with the title “von Seysenegg.” Hismother, Hermine Fenzl, was a daughter of the botanist Eduard Fenzl, director of the Botanical Insititue and Garden of the University of Vienna. Tschermak’s older brother Armin, who married a daughter of the geologist Albrecht Penck, became professor of physiology at Ferdinand University in Prague and , after 1945, at the Univeristy in Regensburg for a few years. His sister Silvia was a mineralogist.

With his brother, Tschermak attended the humanistic Gymnasium at the Kremsmünster monastery (in Upper Austria). In 1891 he enrolled simultaneously at the University of Vienna and at the Hochschule für Bodenkultur at Vienna. After two semesters he volunteered for one year’s work on a nobleman’s estate near Freiberg, Saxony, in order to learn the basics of agricultural praactice. He subsequently continued his studies at the University of Halle, where he took the agricultural examination for the agricultural diploma in 1895 and the following year obtained the Ph.D. with a dissertation in botany.

Tschermak, a Roman Catholic, married twice but had no children. In his autobiography he writes that he was a weak and sickly child; nevertheless, he lived to be nearly ninety-one. Although he suffered greatly in his last years from arthritis in his hands, he never lost his zest for work, his good humor, his kindness, or his enjoyment of social life.

Tschermak held honorary doctorates from the universities of Vienna, Giessen, and Ghent as well as from the agricultural universities of Vienna, Berlin, and Brno. He was a member of the Institut de France, of the Leopoldina Carolina in Halle and of the Max Planck Society, as well as numerous scientific societies and associations. He was awarded the Cothenius Medal and the Goethe Medal.

After completing his studies at Halle, Tschermak was employed at the agricultural stations at Stendal and Quedlingburg, Germany. In 1898, in Ghent, he studied breeding of vegetables and flowers. Stimulated by Darwin’s The Effects of Cross and Self Fertilization in the Vegetable Kingdom (1876), Tschermak began hybridization experiments with various types of peas at the botanical garden in Ghent. The results of this research led to his rediscovery of Mendel’s laws of heredity, which had been disregarded until then and had been rediscovered independently and simultaneously by Hugo de Vries in Amsterdam and by Carl Correns in Leipzig. The publications of these three investigators appeared nearly simultaneously in 1900. Tschermak’s papers appeared in Zeitschrift für das landwirtschaftliche Versuchswesen in Österreich and in summary form in Berichte der Deutschen botanischen Gesellschaft.

Tschermak’s greatest service was his exclusive, immediate recognition of the importance of Mendel’s laws of heredity and his application of these laws in his own breeding experiments. In 1900 Tschermak became an academic lecturer at the Hochschule für Bodenkultur, where he taught theory of plant production, commercial cultivation of plants, and production of vegetables in fields. In 1902 he became assistant to the professor of the theory of plant breeding; in 1906 he was appointed extraordinary professor; in 1909 he was made ull professor. In addition to teaching, Tschermak was for several years director of the Royal Institute for Plant Breeding of the Prince of Liechtenstein (later the Mendel Institute) in Eisgrub, Moravia.

Tschermak traveled extensively to acquire new experience in his field. He made four visits to Sweden, where he served as adviser on the expansion of the Swedish Seed Association at Svalöf. He had a warm relationship with the director of this institute, Nilsson-Ehle, and with his successor. In 1909 Tschermak traveled to the United States with his freind Kurt von Rümker, primarily to meet Luther Burbank and to study his methods. He revisited the United States the following year.

While he was at the Hochschule für Bodenkultur, Tschermak made many new crosses of cultivated plants that increased their diversity and value. Since he had only limited experimental facilities available, he frequently turned over the testing and propagation of his new plants to capable agricultural businesses and to interested farmers, many of whom had established test plots at his suggestion. Of special practical importance were Tschermak’s new types of rye, wheat, barley, oats, and legumes. His breeding of short-shooted edible types of pumpkins with soft-shelled, oil-rich seeds (later known as Tschermak’s pumpkin) made possible a broader use. Also of great value were his new varieties of flowers, such as the gillyflower (Matthiola), and many new types of primroses.

Tschermak’s more than 100 publications are impressive because of the diversity and originality of his investigations, observations, and theories. His most important achievement, the rediscovery of Mendel’s laws, was closely related to his observations of the xenia phenomenon of various plants: in certain instances the seeds in the female plant show effects that are transmitted through the pollen of the male plant. Tschermak investigated the xenia phenomenon in a group of legumes as well as in various types of corn and in the gillyflower. The well-known xenia of the corncob, which manifests itself in various colors and types of surfaces of the kernels, has been extensively investigated by Correns.

Tschermak also was interested in the stimulation effects of alien pollen. He interpreted his findings on fertilization by irritation to mean that nonfertilizing pollen and even dehydrating agents can cause a physiological stimulation of the mature egg cell, and initiate parthenogenetic development.

Tschermak’s discovery and elucidation of a cryptomeric heredity among the gillyflowers is a classic work in theoretical genetics. Here, white-flowered hybrids from white-flowered parents can produce “nova” plants bearing colored flowers in the F₂ generation, if each of the parents possesses a dominant and a recessive gene for white flowers.

Tschermal’s investigations of intergeneric hybridization led to basic discoveries about hybridization. He suspected that various of his fertile intergeneric hybrids, such as that of wheat and rye-the fertile hybrids of Aegilops ovata (2n = 28) and Triticum disccoides (2n = 28)-had been produced by the fertilization of unreduced F₁ gametes. For this hybrid, Aegilotriticum (2n = 56), the additive hybrid number of chromosomes could be demonstrated by cytological examination. This was the first artificially produced and cytologically demonstrated additive intergeneric hybrid of the Gramineae. Today the polyploidization of sterile F₁ hybrids is one of the techniques for the experimental investigation of relationships, as well as for the breeding of artificial, synthetic types of cultivated plants.

Tschermak demonstrated his diverse abilities in the breeding of agricultural and garden plants, for which he used his highly developed technique of hybridization. He was concerned primarily with such difficult problems as combining early ripening with high yield, which he achieved.

The Tschermak-grafted Marchfeld rye, originally bred by selection of the grain and of the offspring without interbreeding with foreign stock, is the only grain variety that has not yet been surpassed in yield (Marchfeld, near Vienna) by any other type, either foreign or domestic. For the self-pollinating types of grain such as wheat, barley, and oats, on the other hand, the new varieties obtained by continuous hybridization yielded 25–50 percent more than the older ones.

Today Tschermak’s fundamental idea, the systematic combination of genes, and the method derived from Mendel’s “laws of segregation “for the investigation of the offspring of single individuals isolated from hybrid populations, have become a matter of routine in the breeding of cultivated plants.

BIBLIOGRAPHY

A detailed account of Tschermak’s life and a complete bibliography of his works are in his autobiography, Erich von Tschermak-Seysenegg, Leben und Wirken (Berlin-Hamburg, 1958).

His works include “Über künstliche kreuzung von Pisum sativum, “in Zeitschrift für das landwirtschaftliche Versuchswesen in Österreich, 3 (1900), 465–555, summarized in Berichte der Deutschen botanischen Gesellschaft, 18 (1900), 232–239; “Über die Züchtung neuer Getreiderassen mittels künstlicher kreuzung, “in Zeitschrift für das landwirtschaftliche Versuchswesen in Österreich, 4 (1901), 1029–1060, and 9 (1906), 699–743; “Über den Einfluss der Bestäubung auf die Ausbildung der ruchthülle, “in Berichte der Deutschen botanischen Gesellschaft, 20 (1902), 7–16; “Über fruchtbare Aegilops-Weizenbastarde, “in Berichte der Deutschen botanischen Gesellschaft, 44 (1926), 110–132, written with H. Bleier; “Zur zytologischen Auffassung meiner Aegilotricum-Bastarde und der Artbastarde überhaupt. Theorie der Chromosomenaddition oder Kernchimärie,” ibid., 47 (1929), 253–261; “Bemerkungen über echte und falsche Grössen-Xenien, “in Zeitschrift für pflanzenzüchtung17 (1932), 447–450; “Über einige Blütenanomalien bei Primeln und ihre Verebungsweise,” in Biologia generalis, 8 (1932), 337–350; “Der schalenlose Kürbis als Ölfrucht, “Deutsche Landwirtschaftliche Presse, 61 , no. 3 (1934); and “Reizfruchtung (Samenbildung ohne Befruchtung), “in Biologia generalis, 19 (1949), 3–50.

Richard Biebl