An efficient method to instantly assess drought-tolerant plants after germination is using
osmoregulation in tissue culture media. In this study, the responses of three Iranian melon genotypes
to sorbitol (0.1, 0.2, and 0.4 M) or polyethylene glycol (PEG) (0.009, 0.012, and 0.015 M) were evaluated
as drought stress simulators in MS medium. ‘Girke’ (GIR), ‘Ghobadloo’ (GHO), and ‘Toghermezi’
(TOG) were the genotypes. GIR is reputed as a drought-tolerant genotype in Iran. The PEG or sorbitol
decreased the coleoptile length, fresh weight, and photosynthetic pigments content while enhancing
proline and malondialdehyde (MDA) contents. Protein content and antioxidant enzyme activity
were utterly dependent on genotype, osmotic regulators, and their concentration. Coleoptile length,
root and shoot fresh weight, root dry weight, proline and MDA content, and guaiacol peroxidase
(GPX) activity can be used as indicators for in vitro screening of Cucumis melo L. genotypes. The
results showed that sorbitol mimics drought stress better than PEG. Overall, our findings suggest
that in vitro screening could be an accurate, rapid, and reliable methodology for evaluating and
identifying drought-tolerant genotypes