Abiotic Stress Effects on Sorghum Leaf Dhurrin and Soluble Sugar Contents throughout Plant Development

Abstract

Although cyanogenic glucosides are considered to play important roles in plant growth, development, and resistance against abiotic and biotic stresses, their presence in high concentrations in feed and food can be fatal to animals and humans. Sorghum [Sorghum bicolor (L.) Moench] is cyanogenic, and the cyanide potential varies with environmental factors, management, and genetic background. Acyanogenic lines have not been identified to date in natural collections. Although the variability of cyanide potentials in seedlings and leaves of plants at early growth stages has been highly researched, few works have looked beyond these stages, especially under variable environmental factors such as water deficit stress. Here, we evaluated 40 diverse sorghum lines for leaf dhurrin and soluble sugar content at various crop developmental stages and variable water availability. Five lines were identified with little‐to‐very low leaf dhurrin content across developmental stages and water availability. Leaves of 30‐d‐old sorghum plants had less cyanide potential than at later stages. A brief preflowering water stress, imposed at booting to flowering, decreased leaf dhurrin and soluble sugar contents, whereas a brief postflowering water stress or prolonged preflowering water stress increased dhurrin and soluble sugar contents. Rapid and efficient screening of dhurrin levels within existing sorghum germplasms could lead to the identification of additional lines with very low to nondetectable dhurrin levels, which will have an enormous impact on sorghum breeding and increase the agronomic value of the sorghum crop.

The Interplay Between Water Limitation, Dhurrin, and Nitrate in the Low-Cyanogenic Sorghum Mutant adult cyanide deficient class 1

“…Drought is known to affect concentrations of cyanogenic glucosides in many species, generally affecting an increase in concentration in both field and controlled environments as reported in cassava (Brown et al, 2016), eucalypt ( Eucalyptus cladocalyx ) (Gleadow and Woodrow, 2002b), white clover ( Trifolium repens ) (Hayden and Parker, 2002), and lima bean ( Phaseolus lunatus ) (Ballhorn et al, 2011). In sorghum, the concentration of dhurrin may increase or decrease depending on tissue-type and the length and severity of stress (Wheeler et al, 1990; O’Donnell et al, 2013; Gleadow et al, 2016a; Emendack et al, 2018). Increases in dhurrin appear to be associated with chronic stress (Wheeler et al, 1990), though reproducing precise levels of water limitation over extended periods and under controlled conditions is challenging (Flower et al, 1990; Tangpremsri et al, 1991; Passioura, 2006; Sabadin et al, 2012).…”

“…Developmental regulation of dhurrin formation in sorghum is confounded by environmental factors such as drought and nitrogen application that can induce higher dhurrin concentrations (O’Donnell et al, 2013; Neilson et al, 2015; Gleadow et al, 2016a; Blomstedt et al, 2018; Emendack et al, 2018). This renders crop toxicity difficult to predict.…”

“…This renders crop toxicity difficult to predict. Toxicity predictions are further complicated due to high variability between lines and individuals within lines (Hayes et al, 2015; Emendack et al, 2018). Moreover, the degree of HCN induction appears to differ depending on whether the stress is chronic or acute (Wheeler et al, 1990).…”

Cyanogenese in Futterpflanzen und Auswirkungen in der Wiederkäuerernährung

“…Es soll hier auch exemplarisch auf die Ergebnisse der intensiven Untersuchungen eingegangen werden, welche die Forschung zur Erkenntnis der Wir-kungsweise von Blausäure darstellt. Als Folge von Stress durch zunehmende Sommertrockenheit (O'Donnell et al, 2013;Emendack et al, 2018) steigt der Gehalt von Blausäure und somit auch die Vergiftungsgefahr bei Menschen und Tier.…”

Time point- and plant part-specific changes in phloem exudate metabolites of leaves and ears of wheat in response to drought and effects on aphids

“…There is support for all three hypotheses, depending on the insect species, its feeding guild, developmental stage and the magnitude of stress applied [18][19][20][21]. The latter is directly related to the number of drought cycles plants are exposed to [22] but also to the phenology of the plants [23].…”