*3.2. Effect of Osmotic Stress Induced by PEG 600 on In Vitro Shoot Cultures*

3.2.1. Changes in the SI of Survival Rate (SISR)

The SISR values for survival rate decreased as PEG 600 level increased (Table 6, Figure S5a–c). At the lowest (2.5%) concentration of PEG 600, the SISR values of survival rates were usually higher than 70, and some breeding lines reached 100. Only explants of C9 and C32 lines survived in significantly lower rates than referent lines. The 5% level of PEG 600 resulted in significant decreases in the survival rates of several tested breeding lines and of the referent lines. Compared to the referent lines, higher values were obtained for the C57, C58 and C19 lines, although results differed significantly only when they were compared to the C107 referent line (its SISR was 69). Moreover, C19 and C20 breeding lines showed very good survival ability, too. Similarly, significantly higher survival rates were obtained for the C20 breeding line compared to both referent lines, although the highest concentration of PEG 600 (7.5%) significantly reduced the SISR in each genotype. In contrast, most breeding lines showed lower survival rates compared to the referent lines, and most frequently the differences were significant.

**Table 6.** Survival rate SI (SISR) values of potato genotypes under osmotic stress induced by PEG 600 added to the medium at level of 2.5%, 5.0% and 7.5%.



**Table 6.** *Cont.*

Symbols mark significant differences from the C107 referent line (-), or from the C103 referent line () according to LSD test; the small letters indicate significantly different means between the breeding lines within a treatment, and the capital letters indicate significantly different means between treatment levels within a breeding line according to Tukey-B test.
