By J. Travis

BRÜNN, Austria, March 1865—It may be the most interesting research on peas since noted Danish science writer Hans Christian Andersen reported that the legume causes insomnia among princesses. An Austrian monk has spent the past decade growing pea hybrids and religiously recording how certain physical traits—pod color, seed shape, and plant height, among others—pass from one generation to the next. He now claims to have found that a few simple rules govern the process.

Johann Gregor Mendel of St. Thomas Monastery, who described his results at this and last month's meetings of the Natural Sciences Society in Brünn, says that physical traits in other plants, as well as animals, may follow similar principles in their inheritance. "I am convinced that it will not be long before the whole world acknowledges the results of my work," he told Science News.

In his experiments, Mendel examined more than 28,000 pea plants, noting seven traits that each come in two easily distinguishable forms. For example, pods of a pea plant are either green or yellow; their seeds, round or wrinkled; and their height, tall or dwarfed.

To create his hybrids, Mendel brushed the pollen of one pea plant onto the pistils of another. He started by crossbreeding strains that had already proved constant for one form of a trait with strains consistently showing the other form. For example, he crossed a tall strain with one whose stems were always short.

Surprisingly, in light of current hybridization theories, the resulting plants did not show blending of any of the seven physical traits. The crosses between tall and dwarf strains did not produce medium-size plants. Instead, they invariably resulted in tall plants. "Transitional forms were not observed in any experiment," Mendel says.

The monk, who is also a meteorologist, dubs the form of each trait prevailing in the hybrids—green pods, round peas, long stems—"dominant" and the trait that disappears, "recessive." He speculates that through their eggs or pollen, the parents of a hybrid contribute to their offspring an element representing the dominant or recessive trait but not both. Therefore, when pollen and eggs join to form a seed, various combinations of the elements can result, but the presence of a dominant trait will always mask the recessive one.

In further experiments, Mendel allowed his hybrid pea plants to self-pollinate. He discovered that the recessive forms of each trait reappeared in a significant fraction of the offspring, demonstrating that the hybrid somehow continues to carry the recessive element in at least some of its seeds. In one experiment, notes Mendel, hybrids having green pods gave rise to 428 plants with green pods and 152 with yellow ones. Mendel documented similar ratios for all the traits he monitored. He concluded that among the offspring, when two hybrid plants are crossed, the dominant form of a trait generally outnumbers the recessive form 3 to 1.

Moreover, Mendel studied whether choice of one trait, say pod color, influences how often the form of a second trait, such as seed shape, passes from one generation to another. The data clearly indicate that each trait is inherited independently of the other ones, he contends.

Leading botanists contacted by Science News were either unaware of Mendel's data or openly skeptical about his conclusions. The work on peas is intriguing but "incomplete," says German botanist Carl Wilhelm von Nägeli. To confirm its general applicability, von Nägeli argues, Mendel should conduct similar hybridization experiments with other plants, such as hawkweed.

Author’s note:

Biologists consider Mendel the father of genetics, but controversy has long swirled around his work and its supposed rediscovery several decades later by three different researchers. Some historians have argued that Mendel manipulated his data to support his conclusions, while others have challenged whether Mendel’s words truly foreshadow the modern concept of the gene and the laws of inheritance that we now call Mendelian. A great source on the many interpretations of Mendel’s research is MendelWeb (http://www.netspace.org/MendelWeb/), an educational Web site that includes the 1866 paper, both in German and in English, that Mendel wrote from his two lectures in Brünn.

Mendel’s statement that the world will one day recognize his work comes from a quote attributed to him in 1884, a few years before his death. The other quotation from Mendel comes from his 1866 paper on the pea hybridization work. Von Nägeli was one of several dozen prominent botanists to whom Mendel sent copies of his 1866 paper and the only one to correspond at length with Mendel. Von Nägeli’s hawkweed suggestion is infamous among geneticists because the plant happens to reproduce asexually. As a result, Mendel was unable to repeat his pea work with hawkweed, and he eventually abandoned his hybrid research to concentrate on his duties as abbot at the monastery. —J.T.

Mendel, G. 1865. Experiments in plant hybridization. Meeting of the Natural Sciences Society. February/March. Brünn.

Henig, R.M. In press. The Monk in the Garden: How Gregor Mendel and His Pea Plants Solved the Mystery of Inheritance. New York: Houghton Mifflin.

From Science News, Vol. 156, No. 25 & 26, December 18 & 25, 1999, p. viii. Copyright © 1999, Science Service.