Somatic embryogenesis, plantlet regeneration and in vitro flowering from cotyledon culture in a legume oil crop, peanut (Arachis hypogaea L.) under NaCl-stress conditions

Present study aims to establish somatic embryogenesis and plantlet regeneration from cotyledon culture in peanut ( Arachis hypogaea L. cv. TMV13) under NaCl-stress conditions. Cotyledon tissue was found to be efficient for somatic embryogenesis in MS medium fortified with 10mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D). Moreover, in order to achieve salt-tolerant regenerants in peanut, cotyledons were inoculated on MS-medium supplemented with various concentrations of NaCl-salt in presence of 2,4-D (10mg/L). Results indicate that with the increase in NaCl-concentrations in medium, frequency of embryogenic callus formation gradually declines and obtained as minimum (17.1±0.16%) with high concentration (150mM) of NaCl-salt while NaCl (200mM) was proved to be lethal. Further, salt-tolerant embryogenic callus was transferred to medium added with (0.5mg/L, 1.0mg/L, 1.5mg/L, and 2.0mg/L) of BAP in combination with (1.5mg/L) of IAA and NaCl (100mM) for the germination of somatic embryos followed by shoot regeneration. Significantly, the maximum frequency (70.2±0.59%) of shoot regeneration was obtained on medium containing BAP (1.5mg/L), IAA (1.5mg/L) and NaCl (100mM). Moreover, salt-tolerant regenerated shoots were further transferred to medium containing kinetin (1.0mg/L, 2.0mg/L, 3.0mg/L, and 5.0mg/L) along with NAA (1.5mg/L) and NaCl (100mM) for root initiation. The high frequency (51±0.7%) of root regeneration was observed on ½ MS medium containing kinetin (2.0mg/L), NAA (1.5mg/L), and NaCl (100mM). Interestingly, rooting medium fortified with NaCl (100mM) was also proved to be effective for precocious induction of in vitro flowering (26.66±0.12%) in the regenerated plantlets. The regenerated plantlets were further transferred to plastic cup soil and acclimatized under greenhouse conditions. The result indicated, salt-tolerant peanut cotyledon culture also shows In Vitro plantlet regeneration and flower formation.