Evaluation of diverse sorghum for leaf dhurrin content and post-anthesis (stay-green) drought tolerance

Authors: Hayes, Chad; Emendack, Yves; Sanchez, Jacobo; Burke, John; Pugh, Nicholas - Ace; Xin, Zhanguo; ROONEY, WILLIAM - Texas A&M University

Submitted to: Crops
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2023
Publication Date: 9/21/2023
Citation: Hayes, C.M., Emendack, Y., Sanchez, J., Burke, J.J., Pugh, N.A., Xin, Z., Rooney, W.L. 2023. Evaluation of diverse sorghum for leaf dhurrin content and post-anthesis (stay-green) drought tolerance. Crops. 3(3):241-250. https://doi.org/10.3390/crops3030022.
DOI: https://doi.org/10.3390/crops3030022

Interpretive Summary: Post-flowering drought stress, referred to as stay-green, is a desirable characteristic in sorghum. As a drought tolerant crop species, sorghum has traditionally been grown in semi-arid climates, and the identification of sorghum breeding lines that are resistant to drought is crucial. Although there are systems for scoring stay-green in sorghum, the plant traits that actually influence the drought tolerance are not well understood. In addition, the relative effects that different environments can have on stay-green need to be defined. As such, this study sought to determine if there is a relationship between compositional traits, such as leaf dhurrin and sucrose, and stay-green in grain sorghum lines. We found that there is a strong correlation between leaf dhurrin content and stay-green in grain sorghum, indicating that it may be possible to breed for stay-green even in environments that do not experience drought events via identification of lines that produce high amounts of dhurrin. In addition, we found that measures of these traits were repeatable across different environments, indicating that similar results could likely be observed within similar future environments and sorghum lines. Further study will need to be conducted to determine why leaf dhurrin content affects stay-green and to define the nature of the relationship between the two traits.

Technical Abstract: Post-flowering drought tolerance (stay-green) in grain sorghum [Sorghum bicolor (L.) Moench] is an important agronomic trait in many arid and semiarid environments throughout the world. Stay-green has been associated with increased grain yields, as well as resistance to lodging and charcoal rot disease. Nonetheless, the relative effects of genotype, environment, and genotype x environment interactions are not well understood for the trait; similarly, the relationship between various leaf sugars and stay-green has not been heavily evaluated in diverse germplasm. Thus, the goals of this study were to determine genotype, environment, and GxE effects for leaf dhurrin, sugars, and stay-green in ten diverse grain sorghum breeding lines, to evaluate Pearson’s correlation coefficients (r) between these traits, and to determine entry-mean repeatability (R) for each of these traits. Of the compositional traits studied, we determined that leaf dhurrin had the highest correlation with stay-green phenotypes (r = -0.62). We found that stay-green sorghum lines contained approximately 2 – 3 times as much dhurrin as non-stay-green lines, with B1778 containing the highest concentrations of dhurrin (84.8 µg/cm2) and Tx7000 containing the least (20.9 µg/cm2). The differences between environments for several of the traits was high, and all the traits examined had high repeatability (R = 0.89 – 0.92). These data demonstrate a relationship between leaf dhurrin and stay-green phenotypes in sorghum, and further study will allow researchers to determine the causal effect that dhurrin has on post-flowering drought tolerance in sorghum.