Physiological response and comparison of Sorghum sudanense and S. bicolor × S. sudanense seedlings under drought stress

The physiological responses of nine cultivars of Sorghum sudanense and three cultivars of S. bicolor × S. sudanense were studied under drought stress induced by polyethylene glycol 6000 (PEG-6000) based on a sand culture experiment. The results show that materials with better drought tolerance have better water retaining capacity, higher chlorophyll content, and better photosynthesis and membrane integrity under drought stress. The drought tolerance of the 12 cultivars were evaluated by subordinate function values analysis according to seven physiological parameters (leaf relative water content, electrolyte leakage, malondialdebyde content, chlorophyll content, photochemical efficiency, net photosynthetic rate, and water use efficiency). Three S. sudanense cultivars (No. 1, 2, and 3) and cultivar No. 10 (‘Shucao No. 2’ S. bicolor × S. sudanense), cultivar No. 11 (‘Shucao No. 1’ S. bicolor × S. sudanense), and cultivar No. 12 (‘Hay-King’ S. sudanense) had higher drought tolerance, and two S. sudanense cultivars (No. 7 and 8) and a S. bicolor × S. sudanense cultivar (No. 9) had lower drought tolerance. This study provides basal data for the cultivation and utilization of forages and selection of new cultivars with higher drought tolerance.