Identification of Chromosomes that Condition Dhurrin Content in Sorghum Seedlings¹

Abstract

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 1‐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 dharrin content on at least 5 of the 10 chromosome pairs.

Natural Variation in Synthesis and Catabolism Genes Influences Dhurrin Content in Sorghum

“…Transcriptional regulation of the biosynthetic section of the pathway was previously reported, and induction by nitrogen fertilization in older plants was observed (Busk and Møller, 2002). It is hypothesized that genetic variation contributes to differential dhurrin content among sorghum cultivars, as evidenced by a number of studies indicating distinct quantitative differences (Gillingham et al, 1969; Gortz et al, 1987; Burke et al, 2013). However, to date there is limited information on the genetic control of dhurrin content in sorghum.…”

Cyanogenese in Futterpflanzen und Auswirkungen in der Wiederkäuerernährung

“…McFarlane et al (1974 konnten zeigen, dass ein zellfreies System in der Lage ist, L-Tyrosin unter Zugabe entsprechender Reaktionspartner zu dem entsprechenden cyanogenen Glykosid, in diesem Fall also zu Dhurrin, umzuwandeln, was spätere Studien bestätigten (Møller und Conn, 1979). Sowohl in den Samen als auch in der älteren Sorghum-Pflanze ist der Cyanidgehalt stark vom genetischen Hintergrund und von den Umweltbedingungen abhängig (Nelson, 1953;Gorz et al 1987;Hayes et al, 2015). Es wird aufgrund des signifikanten Umsatzes von Dhurrin in den Samen angenommen, dass sowohl Änderungen als auch der Ausfall der Synthese, die Dhurringehalte regulieren können.…”