Ethionine, a chemical analogue of methionine, is highly toxic to most organisms (Alix, 1982).
Seven rolls were placed vertically in a sterile cup 10 cm in diameter containing 250 mL of aqueous ethionine (0.75 mM), and the rolls and the upper portion of the cup were enclosed with a large plastic bag.
On 30 May 1997, 60 M3 seeds from each of seven high seed-sulfur lines obtained by field phenotype selection and 60 M4 seeds from each of 10 lines obtained by ethionine screening were field planted at Hinds Farm, Ames, IA, for crossing.
M1 seeds (50 568) were germinated in the presence of 0.75 mM aqueous ethionine and screened for ethionine resistance by relative root length, dark green leaf coloration, and plant growth rate (see Methods).