This study carried out in order to investigate the effects of salinity on carbon isotope discrimination (∆) of shoots and roots of four sugar beet cultivars (cv) including Madison (British origin) and three Iranian culivars (7233-P12, 7233-P21 and 7233-P29). Plants were grown in sand culture medium in greenhouse conditions. Plants irrigated with saline water (tap water as control, 50 mM, 150 mM, 250 mM and 350 mM of NaCl + CaCl2 in 5 to 1 molar ratio) from 4 leaves stage for 16 weeks. Carbon isotope discrimination significantly decreased with increasing salinity. Significant differences of ∆ between shoot and root were observed in all cvs and all levels of salinity. Madison cv showed lower ∆ in shoot and root than other three cvs at all levels of salinity expect control, but cv 7233-P29 had significantly higher ∆ values at saline conditions of 150 mM and above. Therefore, ∆ might be applicable, as a useful tool, for study of salinity tolerance of sugar beet genotypes.

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