Somatic embryogenesis and in-vitro regeneration of rice (Oryza sativa L.) cultivars under one-step and multiple-step salinity stresses

The present study aimed to examine the effect of one-step and multiple-step salinity stress on the somatic embryogenesis of rice cultivars within the solid and liquid (cell suspension) culture media conditions. Five rice cultivars, including Puteh Perak, Mahsuri, Basmati-370, Nona Bokra and Khari Gunja were used in this study. The callus cultures were induced from the rice seed embryo using solid MS media containing 10 μM 2,4-D and 2 μM Kinetin. The results indicated that in the one-step NaCl treatment, the growth of the control calli and cell suspensions of the cultivars was decreased, and significant morphological changes were observed. In contrast, the multiple-step NaCl treatment of the calli and cell suspensions led to higher growth of the cultures in the presence of NaCl compared to the controls. The solid MS media, containing 3 μM IAA and 40 μM Kinetin performed as the best media for plant regeneration in both calli and cell suspensions. The regeneration capacity of the one-step treated calli and cell suspensions were decreased with the increased concentration of NaCl in the media. Higher regeneration frequencies occurred in the multiple-step treated calli of Pueth Perak and Nona Bokra compared to their controls while the other cultivars showed a lower regeneration under the same trend of salinity. The plant regeneration capacity of the multiple-step treated, as well as the control cultures, was decreased with increasing the cultures age. However, the NaCl-treated cultures maintained higher regeneration capacity under the both modes of treatment (one-step and multi-step) for up to 48 weeks compared to the control treatments.