3.2.2. Changes in the SI of Shoot Length (SISL)

Each breeding line and both referent lines responded with significantly decreased shoot lengths to the presence of PEG 600 at a concentration of 2.5%, and inhibition of shoot growth increased with increasing PEG 600 concentration (Table 7, Figure S6a). Referent genotypes showed very good stress tolerance compared to breeding lines. SISL values of C103 were higher than those of C107 at each level of PEG 600, and differences between SISL values of referent lines increased as PEG 600 level increased. When 2.5% PEG 600 was applied, only the SISL values of C6 and C42 were significantly higher than those of both referent lines. In addition to them, the C19 breeding line showed very good SISL results in both treatments by 2.5% and 5.0% PEG 600 (SISL were 75 and 53.9, respectively). At the highest level of PEG 600 treatment, the C103 referent line achieved the significantly best SISL result, followed by the C107 referent line, but lagging far behind.


**Table 7.** Shoot length SI (SISL) values of potato genotypes under stress treatment induced by PEG 600 added to the medium at levels of 2.5%, 5.0% and 7.5%.


**Table 7.** *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.
