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Young plants of sorghum and sudangrass [Sorghum bicolor (L.) Moench) may be toxic to livestock because of the presence of the cyanogenic glucoside, dhurrin [p-hydroxy-(S}-mandelonitrile-β-Dglucoside), in the forage. In the present study a set of 11 chromosomal reciprocal translocations in 'Combine 7078' grain sorghum, involving each of the 10 chromosome pairs of sorghum in at least two of the translocations, was used to determine which chromosomes carried genes conditioning dhurrin content of sorghum seedlings. Each translocation stock was crossed and backcrossed once to a low-dhurrin line of sudangrass. Backcross progenies and parental plants were started in the greenhouse, and 100 plants of each backcross and 50 of each parental stock were transplanted to a field nursery in a randomized complete block design with five replications. Individual backcross plants were classified as semisterile or fertile on the basis of seed set. They were also classified for high or low dhurrin content based on a spectrophotometric assay of first leaves of l-week-old seedlings grown from selfed or open-pollinated seed that had been harvested from the backcross plants. Results suggested the presence of one or more genes conditioning dhurrin content on at least 5 of the 10 chromosome pairs.