Abiotic stress affects on sorghum leaf dhurrin and soluble sugar contents throughout plant development

Authors: Emendack, Yves; Burke, John; ECHEVARRIA LAZA, HAYDEE - Texas Tech University; Sanchez, Jacobo; Hayes, Chad

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2018
Publication Date: 6/21/2018
Citation: Emendack, Y., Burke, J.J., Echevarria Laza, H., Sanchez, J., Hayes, C.M. 2018. Abiotic stress affects on sorghum leaf dhurrin and soluble sugar contents throughout plant development. Crop Science. 58:1706-1716. doi:10.2135/cropsci2018.01.0059.
DOI: https://doi.org/10.2135/cropsci2018.01.0059

Interpretive Summary: Sorghum produces the poisonous hydrogen cyanide from the metabolite dhurrin which is present in all its vegetative tissues. The amount produced varies with environmental factors, management, and varieties used. The cyanide poisoning in seedlings and leaves of younger plants have been shown to be very high especially when plants are water stressed. Research on cyanide potential at later developmental stages are few, and to date no variety without hydrogen cyanide poisoning potential has been identified in natural collections. In this article, researchers report on multi-year studies where 40 diverse sorghum lines were evaluated for their cyanide poisoning potential throughout plant development and under water deficit stress. Researchers were able to identify 5 sorghum lines with very low to non-detectable dhurrin content in the leaves even under water stress and at all stage of crop development. Also, researchers showed that 30 day old sorghum has a lower chance of cyanide poisoning than at other developmental stages. Given the need for sorghum varieties with no cyanide poisoning potentials in the feed and food industries, the identification of the five lines will have enormous agronomic impact to sorghum farmers and producers if they are successfully introgressed into elite sorghum varieties or hybrids.

Technical Abstract: Though 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 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. While the variability of cyanide potentials in seedlings and leaves of plants at early growth stages have been highly researched, very 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 day-old sorghum plants had less cyanide potential than at later stages. A short pre-flowering water stress, imposed at booting to flowering, decreased leaf dhurrin and soluble sugar contents, while a short post-flowering water stress or prolonged pre-flowering 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-non-detectable dhurrin levels which will have an enormous impact on sorghum breeding and increase the agronomic value of the sorghum crop.