Ability of a Forage and Grain Sorghum (Sorghum bicolor L.) Variety to Tolerate Water Stress during Germination and Salt Stress at Early Growth Stages.

Sorghum is being explored in California as a multi-utility, water-use efficient crop. However, water stress during germination periods and salt stress during the growing period are common occurrences for annual crops in California’s southern San Joaquin Valley. Therefore, experiments were conducted to determine the efficacy of water stress on seed germination and salt stress during the early growth stage of a selected forage and a grain sorghum variety.  Eight water potential (ψ) solutions ranging from 0 to −5.56 MPa were prepared using polyethylene glycol (PEG) and germination of the seeds were tested in these solutions in a growth chamber set at constant temperature of 30 ± 3° C. Germination was recorded for two weeks. For the salt stress study, potted sorghum plants were grown under ambient field conditions. Each plant was irrigated with 100 to 300 ml of either 0, 5, 10, 15, or 20 ds m^-1 sodium chloride (NaCl) solutions applied in the pot on alternate days from two weeks after emergence to six weeks after emergence. Plant growth parameters were measured every week and the plants were destructively harvested at six weeks after planting and their dry weights were recorded. Germination of the forage and grain sorghum variety was reduced by 50% at approximately -2.5 MPa and -1.5 MPa, respectively. The tolerance of the forage sorghum variety to water stress might be due to the presence of tannins in the pigmented testa and this will be further explored. Total aboveground biomass of the plants declined at soil salinity treatments greater than 5 ds m^-1 with a 50% reduction at approximately 7 ds m^-1.