Early Seedling Growth Characteristics Relate to the Staygreen Trait and Dhurrin Levels in Sorghum

Abstract

Dhurrin content in leaves of the mature sorghum [Sorghum bicolor (L.) Moench] plant is a quantitative measure of the level of pre‐ and postflowering drought tolerance, with high dhurrin contents expressed in postflowering drought‐tolerant lines. Postflowering drought tolerance in sorghum has been linked to the staygreen trait and associated with increased grain yield during postanthesis stress. Seasonal variability in postflowering drought occurrences makes selection for the staygreen trait unpredictable and the efficiency and reliability of screening for the trait using only conventional breeding low. Differences in dhurrin content between high and low dhurrin levels lines is only markedly favored to the high dhurrin level lines in the upper leaves of matured field‐grown plants. Here we report a screening method using early seedling growth characteristics of sorghum lines of known dhurrin level grown in sand with no inorganic nutrients supply. The method was evaluated under cold and warm temperatures. Seedling growth characteristics and contents of dhurrin and high‐performance liquid chromatography‐detected sugars were determined at 5, 10, 17, and 23 d after emergence. High dhurrin level lines had larger increases in shoot fresh weight, dried weight, and length than did lines with low dhurrin levels at 10 d after emergence under both temperatures. Similar trends were observed when separating lines into high and low dhurrin levels using fresh shoot mass and length at 10 d after emergence. Dhurrin content decreased with seedling age, was statistically similar between dhurrin levels, and negatively correlated to concentrations of sugar. Thus, selecting for postflowering drought tolerance can be timely, reliably, and inexpensively done using early seedling growth characteristics.

Amylopectin Chain Length Dynamics and Activity Signatures of Key Carbon Metabolic Enzymes Highlight Early Maturation as Culprit for Yield Reduction of Barley Endosperm Starch after Heat Stress

“…In sorghum, stay green has for instance been associated with the formation and presence of the cyanogenic glucoside dhurrin (Hayes et�al. 2015, Emendack et�al. 2017).…”

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

“…The difference in leaf dhurrin content for low-and high-dhurrin lines is only eminent when measured from fully developed leaves of mature plants (Burke et al, 2013). However, Emendack et al (2017) reported greater fresh shoot biomass for high-dhurrin seedlings 10 DAE, grown in nutrient-deficient play sand. In addition, during early seedling development, ?75% of the endosperm sugar content (including glucose, fructose, and sucrose) is depleted by 8 d after sowing (?4 DAE) (Newton et al, 1980).…”

“…Coupled with this is the fact that even though cyanogenesis is a stable heritable trait with all individuals in some species being cyanogenic, others can be highly polymorphic, with phenotypically acyanogenic individuals ( Jørgensen et al, 2005a;Zagrobelny et al, 2008). Emendack et al (2017) reported that seedlings of high-dhurrin genotypes have greater fresh shoot biomass than low-level genotypes at 14 DAE when grown in nutrient-deficient play sand at optimum climatic conditions. Thus, there may be very low dhurrin levels or acyanogenic sorghum cultivars in other germplasms.…”

“…Like >3000 plant species from all major vascular plant taxa belonging to >130 families of flowering plants, sorghum is cyanogenic, with the cyanogenic glucoside dhurrin [( S )‐p‐hydroxymandelonitrile‐β‐D‐glucopyranoside] found in all its vegetative tissues, with higher concentrations in the leaves. The biological functions of cyanogenic glucosides include use as herbivore repellant (Jones, 1998; Tattersall et al, 2001; Gleadow and Woodrow, 2002a; Zagrobelny et al, 2004), antifungal activity (Siebert et al, 1996), N turnover, transport, and storage (Kongsawadworakul et al, 2009; Møller, 2010; Emendack et al, 2017), osmoprotectant properties (Burke et al, 2015), and as a metabolite associated with the stay‐green trait (Hayes et al, 2015; Emendack et al, 2017). Cyanogenic glucosides are considered to play important roles in plant growth, development, and resistance against abiotic and biotic stresses (Gleadow and Møller, 2014; Pičmanová et al, 2015).…”

Agro-morphological characterization of diverse sorghum lines for pre-and post-flowering drought tolerance

“…These genotypes maintain green leaf area and hence photosynthetic capability and/or improved translocation of carbohydrates under late season moisture stress, and produce higher grain yields compared with senescent genotypes (Borrell and Douglas, 1997;Borrell et al, 2003). Staygreen genotypes have also been shown to have a comparatively higher level of the secondary metabolite dhurrin (a Cyanogenic glucoside with nitrogen storage function) in leaves of matured plants at the late vegetative stage (Burke et al, 2013), and 10-day old seedlings of staygreen lines showed higher biomass than senescent lines under nitrogen limiting conditions (Emendack et al, 2016).…”