Agronomy and Horticulture, Department of


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Published in Crop Science (July-August 1977) v. 17: 578-582.


A method of assessing the hydrocyanic acid potential (HCN-p) of sudangrass [Sorghum sudanense (Piper) Stapfl and sorghum [S. bicolor (L.) Moench] seedlings is described. This procedure is based on the determination of p-hydroxybenzaldehyde (p-HB), which is released upon hydrolysis of dhurrin, the cyanogen normally present in plants of Sorghum species. Extraction and hydrolysis of dhurrin are accomplished by autoclaving young leaf tissue in water. The content of p-HB in the aqueous extract is then determined by spectrophotometric assay in alkaline solution at 330 nm. Uniform samples for the comparison of widely divergent genotypes are obtained by using the first leaf of young, chamber-grown green seedlings. Relative ranks of a wide variety of sorghum germplasm assayed for HCN content by this technique are in good agreement with those obtained by other methods. The procedure shows promise of providing a rapid and precise tool for conducting genetic and breeding studies with sorghums.