Dawn of Modern Wheat Genetics: The Story of the Wheat Stocks That Contributed to the Early Stage of Wheat Cytogenetics

Abstract

This story began in October, 1913, with a letter from Konstantin Flaksberger, Bureau of Applied Botany, Russia, wrote to Yuzo Hoshino, Hokkaido University, Japan, requesting seeds of Japanese cereals. Handed his letter by Hoshino, Takajiro Minami, Director of the University’s Experimental Farm, responded by sending Flaksberger seeds of oats and barley in December, 1913, and of barley and wheat in September, 1915. Minami then asked Flaksberger for Russian wheat and other cereals, and acknowledged their receipt in May, 1916, after which their correspondence ceased. Tetsu Sakamura had been a graduate student in the Faculty of Agriculture, Hokkaido University since 1913, carrying out chromosome studies of leguminous species, but he switched to wheat in 1916, asking Minami to provide wheat seeds. Using material that originated from Flaksberger, Sakamura determined the correct chromosome numbers of eight wheat species, among which he discovered polyploidy of 2n=14 (2x), 28 (4x), and 42(6x); these results were published in July, 1918, and in December he left to study overseas for two years. When Hitoshi Kihara entered the graduate course of Hokkaido University in August, 1918, he received Sakamura’s materials and started genome analytical work, demonstrating that the set of seven chromosomes of common wheat, which did not exist in tetraploid wheat, was the unit in chromosome transmission as well as in fertilization, thus proposing the concept of the genome. He extended genome analysis to most species of the Triticum–Aegilops complex, determining their genome constitution. His interest then turned to interaction between the nucleus and cytoplasm, and he found that the cytoplasm of Ae. caudata caused male sterility, leading to the discovery of cytoplasmic male sterility in wheat. In 1973, Tsunewaki’s group in Kyoto University started an investigation on differentiation of plasmon in the Triticum–Aegilops complex; plasmons of this complex were introduced into 12 wheat genotypes, including three of Flaksberger’s stocks, as a result of which 552 alloplasmic lines were produced; their phenotypes and restriction fragment patterns of organellar DNAs were compared. Combining the results of their plasmon analysis and Kihara’s genome analysis, the maternal and paternal lineages of most species in this complex were finally determined.