Early seedling growth characteristics relates to the stay-green traits and dhurrin levels in sorghum

Authors: Emendack, Yves; Chopra, Ratan; Hayes, Chad; Sanchez, Jacobo; Burow, Gloria; Xin, Zhanguo; Burke, John

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2016
Publication Date: 10/26/2016
Citation: Emendack, Y., Chopra, R., Hayes, C.M., Sanchez, J., Burow, G.B., Xin, Z., Burke, J.J. 2016. Early seedling growth characteristics relates to the stay-green traits and dhurrin levels in sorghum. Crop Science. 57:1-12.

Interpretive Summary: Dhurrin content in leaves of mature sorghum plant is associated to the level of pre-and postflowering drought tolerance, determined by the staygreen trait. The staygreen trait is associated with increased yield under postflowering drought stress. Selection for staygreen is made difficult because of the seasonal variability in postflowering drought occurrences, and the reliability of screening for the trait using only conventional breeding is 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 using HPLC. Thus screening for dhurrin levels is expensive, laborious, and unpredictable. Here we report significant relationships between early seedling growth characteristics and known dhurrin levels of sorghum genotypes grown in sand with no inorganic nutrient supply under cold and warm temperatures. Seedling growth characteristics and contents of dhurrin and HPLC detected sugars were determined at 5, 10, 17, and 23 days after emergence. High dhurrin levels genotypes showed largest increases in fresh shoot weight, dried shoot weight, and length than did low dhurrin levels genotypes at 10days after emergence under both temperatures. Thus, selecting for postflowering drought tolerance can be timely, reliably, and inexpensively done using early seedling growth characteristics.

Technical Abstract: Dhurrin content in leaves of mature sorghum 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 link to the staygreen trait, associated with increased yield during postanthesis stress. Seasonal variability in postflowering drought occurrences make 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 significant relationships between early seedling growth characteristics and known dhurrin levels of sorghum genotypes grown in sand with no inorganic nutrient supply under cold and warm temperatures. Seedling growth characteristics and contents of dhurrin and HPLC detected sugars were determined at 5, 10, 17, and 23 days after emergence. High dhurrin levels genotypes showed largest increases in fresh shoot weight, dried shoot weight, and length than did low dhurrin levels genotypes at 10days after emergence under both temperatures. Genotypic variations in fresh shoot weight and length showed similar trends (high to low dhurrin levels) in separating genotypes only at 10DAE. Dhurrin contents decreased with seedling age; were statistically similar between dhurrin levels, and negatively correlated to sugar concentrations. Thus, selecting for postflowering drought tolerance can be timely, reliably, and inexpensively done using early seedling growth characteristics.