3.2.4. Changes in the SI of Root Number (SIRN)

The number of roots decreased in the majority of breeding lines when media contained PEG 600, and the SI values decreased as PEG 600 level increased (Table 9, Figure S8a–c). However, SI values of higher than 100 were obtained for the C2 and C3 breeding lines in the 2.5% PEG 600 treatment, and their results were significantly higher compared to those of the referent lines and the majority of other breeding lines when treated with 2.5 and 5.0% PEG 600. In addition, the C42 breeding line also achieved significantly higher SI results with the 5.0% PEG treatment. When 7.5% PEG 600 was added to the medium, the C103 referent line showed the significantly best result (72.2), while the SI value of the other referent line (C107) was significantly lower (57.7) than that of C103, but significantly higher than those of most breeding lines. Moreover, the C2 and C3 breeding lines showed results very similar to those of the C107 referent line.


**Table 9.** Root number SI (SIRN) values of potato genotypes under osmotic stress induced by PEG 600 added to the medium at levels of 2.5%, 5.0%, and 7.5%.

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.
