Fran Jesenko

Fran Jesenko (14 March 1875 – 14 July 1932) was a Slovenian botanist and plant geneticist who became notable for his work on the hybridisation of wheat and rye.

After attending high school in Ljubljana, Jesenko enrolled in the University of Vienna and graduated in 1902. During his studies, he became a tutor to two Oriental princes at Vienna's Teresianum college for boys, later also serving in this capacity for Count Merveldt. His position gave him the opportunity to travel all across Europe and later to Egypt, where he studied desert flora. In 1909, he became a research assistant under Erich von Tschermak at the College of Agriculture (Hochschule für Bodenkultur; now University of Natural Resources and Life Sciences) in Vienna, and a lecturer in 1913.

During his period in Vienna, Jesenko commenced several studies on plant hybridisation under von Tschermak's supervision, obtaining fertile hybrids between different varieties of wheat and rye with the help of backcrossing, and studying their characteristics with reference to Mendelian principles. He proposed that the reduced fertility of hybrids was a consequence of chromosomal incompatibility, as well as morphological differences. With this, he was one of the pioneers of studies on triticale and intergeneric hybrids in general.