Induction of somatic embryo and plantlet regeneration from immature inflorescence culture in kodo millet (Paspalum scrobiculatum L.) under salinity stress conditions

Salinity stress is a major abiotic stress factor that affects plant growth, physiological activities and developmental processes. This study involves establishing efficient somatic embryogenesis and plantlet regeneration system using immature inflorescence of kodo millet ( Paspalum scrobiculatum L. cv. TNAU86) under NaCl-salinity stress conditions. To begin with, the immature inflorescence (0.5cm) of kodo millet was excised from the 40-45 days old field growing plants followed by surface sterilization and inoculation in Murashige and Skoog (MS) medium supplemented with the various concentrations of NaCl (10mM, 25mM, 50mM, 75mM, 100mM, 150mM, and 200mM) salt along with 2,4-Dichlorophenoxyacetic acid (2,4-D) (1.5 mg/L). The results reveal that the maximum mean frequency (89.3±0.3%) of somatic embryogenesis was obtained from embryogenic callus that was growing with medium added with NaCl (50mM) while it was found to be the least mean frequency (12±4.1%) with 150mM of NaCl-salt treatments. Moreover, the highest concentration of NaCl (200mM) salinity was found to be lethal and explants were observed to get gradually necrosed. Later, embryogenic calli showing differentiation of somatic embryos were sub-cultured on basal medium supplemented with 0.5mg/L of 6-Benzylaminopurine (BAP) along with respective concentrations of NaCl-salt for the germination of somatic embryos into plantlets. Significantly, 100mM of NaCl-treatment was proved to show strong inhibitions and thus minimum salt tolerant plantlets regeneration (4±2.21%) was recorded. Further, in vitro grown salinity stress tolerant plantlets were transferred to plastic cups and gradually acclimatized under greenhouse conditions.