Characterizing Parents of Sorghum Mapping Populations Exposed to Water-Deficit Stress during Vegetative Stage.

Changing climate presents new challenges to agricultural production and global climate models project increased intensity and magnitude in water-deficit stress conditions in the future. This is especially challenging for the arid and semi-arid regions of the world, where sorghum forms an important component of the cropping system. The research objective was to characterize 11 genetically and geographically diverse sorghum genotypes for shoot related physiological parameters and changes in the leaf lipidome under water-deficit stress. A lysimetric based experiment was set up in the greenhouse and water-deficit stress (55% to 60% water-holding capacity) was imposed, lasting for 15-days, starting from 35-days after emergence. Gravimetric pot weighing was followed daily to determine transpiration efficiency during this period. The LS-means for cumulative water transpired was 1.77 liters for stressed plants and 7.87 liters for the well-watered plants. Almost all parameters varied significantly between stressed and well-watered plants regardless of genotypic variances. With respect to photosynthetic assimilation, stomatal conductance, stem height, leaf and tiller numbers, effects of the stress was genotype specific. The relationship between transpiration efficiency and Δ¹³C was generally positive but stronger for stressed plants compared to the well-watered plants.  Results from electrospray ionization-tandem mass spectrometry analysis showed significant effects of water-deficit stress on the regulation of leaf membrane lipid composition. In view of sorghum’s adaptation to challenging environmental conditions, findings will provide a means to identify the appropriate mapping population to map genomic regions responsible for increased drought resilience in sorghum.