Application of the salt stress to the protoplast cultures of the carrot (Daucus carota L.) and evaluation of the response of regenerants to soil salinity

This is the first study to generate carrot plants for enhanced salinity tolerance using a single-cell in vitro system. Protoplasts of three carrot accessions were exposed to treatment by seven different concentrations of NaCl (10-400mM). Salt concentrations higher than 50mM decreased plating efficiency and those of 200-400mM of NaCl completely arrested mitotic divisions of cultured cells. The protoplast-derived plants from the control and 50-100mM NaCl treatment were subjected to an 8-week salt stress in greenhouse conditions induced by salinized soil (EC 3 and 6mScm(-1)). 50mM NaCl stress applied in vitro induced polyploidy among regenerated plants. The regenerants obtained from the 50 and 100mM NaCl-treated protoplast cultures grown in saline soil had a higher survival rate compared to the regenerants from the control cultures. The salt-stressed plants accumulated anthocyanins in petioles and produced denser hairs on leaves and petioles in comparison to the control plants. Salt stress influenced pollen viability and seed setting of obtained regenerants. The results suggest that salt stress applied in vitro in protoplast cultures creates variation which allows alleviating the negative effects of salt stress on the development and reproduction of the carrot. Key messageSalt stress applied to carrot protoplasts generates variability manifested in differences in cellular response and variation in ploidy. The adaptation of carrot regenerants to soil salinity was associated with accumulation of anthocyanins and increased hairiness.