Selectable Traits in Sorghum Genotypes for Tolerance to Salinity Stress

Sorghum [Sorghum bicolor (L.) Moench] is moderately tolerant to salinity and it is important as a candidate crop for both fodder and grain in salt-affected areas. This pot experiment was conducted at Research Greenhouse of College of Agriculture, Shiraz University, Iran, to evaluate the relative effectiveness of biochemical traits and stress tolerance indices contributing to genotypic differences in salinity tolerance in 30 lines and 14 cultivars of sorghum. In addition, a new indicator, Storage Factor Index (SFI), was defined and used to quantify the Na+ partitioning between shoot and root. Among the indices, stress tolerance index was found useful as a selection criterion. Furthermore, the tolerant genotypes had higher K^+/Na^+ ratio in shoot and root with greater SFI, indicating that most of Na+ was stored in their roots. Although peroxidase and superoxide dismutase were enhanced under salinity conditions in both sensitive and tolerant genotypes, only Catalase (CAT) activity was found to be promoted in tolerant lines/cultivars. Proline accumulation did not appear to be related to salinity tolerance in sorghum lines/cultivars. Overall, our findings suggested that salinity tolerance in sorghum genotypes was not only associated with Na^+ exclusion from the shoot, but also with the enhancement of CAT activity.