Assessment of the Genetic Variation for Osmotic Stress Tolerance of Some Sorghum [Sorghum bicolor (L.) Moench] Genotypes at Seedling Stage

Abstract

The research work was conducted in order to develop a rapid and effective screening technique to assess the genetic variability of some sorghum genotypes for osmotic stress tolerance during the initial seedling stage and identifying the osmotic stress-tolerant and susceptible genotypes using Z-distribution analysis, in addition to evaluating the relevance of induction in improving the level of osmotic stress tolerance. The experiments were laid according to the simple completely randomized design with three replicates. Increasing the level of osmotic stress in the growth solution caused a significant reduction in the average length of seedlings, which was significantly higher in the control treatment (19.31 cm) and decreased proportionally with increasing the osmotic level in the growing media. The osmotic stress level of -1.8 Mpa caused a reduction the seedling length estimated by 50.03% compared with the control, thereby it could be considered as optimum lethal osmotic level. The reduction percentage in the length of both roots and seedlings was significantly lower (7.77 and 8.45% respectively) at the induction osmotic level of – 0.4 Mpa compared with the other induction levels, so it is considered as the optimum induction level. The reduction percentage in the length of both roots and seedlings was significantly lower in the osmotically induced seedlings (10.87 and 9.37% respectively), while it was significantly higher in the non-induced seedlings (41.75 and 33.17% respectively), indicating the importance of induction to enhance the tolerance capacity of sorghum seedlings to the lethal osmotic stress levels. The sorghum genotypes such as Rizinia and ICSV 25274 are classified as highly osmotic stress tolerant, while the genotypes such as ICSSH 29, ICSV574 and NTJ 2 are classified as highly susceptible genotypes, because the revealed the lowest absolute seedling length and the highest reduction percentage.