Somatic embryogenesis, biochemical alterations and synthetic seed development in two varieties of coriander (Coriandrum sativum L.)

Abstract

Somatic embryogenesis (SE), biochemical alterations and synthetic seed formation were carried out in two Coriandrum sativum L. varieties (Rajendra Swathi ‘RS’ and Co-1). Callus was induced profusely in 1.0 mg/l 2,4-dichlorophenoxy acetic acid (2,4-D) added MS medium but Co-1 had more callus induction frequency (96.0%) compared to RS (89.3%). The callus turned into embryogenic tissue and variable embryogenic frequency (77.6% in RS and 72.8% in Co-1) was noted. Somatic embryos started to differentiate on the same 2,4-D added medium but the numbers of somatic embryos were more in RS (63.0 embryos per culture) compared to Co-1 (51.0 embryos per culture). These somatic embryos progressed well and showed maximum maturation in RS (78.7%) in 0.25 mg/l 6-benzyl adenine (BA) + 0.5 mg/l α-naphthalene acetic acid (NAA) added medium. The biochemical analyses of non-embryogenic-, embryogenic-callus and different stages of embryos were conducted in order to know the changes of physiology in different tissues. Sugar and proline content were noted to be high at embryo induction stage while protein level was higher at embryo maturation stage. Biochemical analysis also revealed that the catalase (CAT) and superoxide dismutase (SOD) activities were higher at maturation stage of embryos compared to other embryogenic stages. Matured somatic embryos were germinated in MS added with 1.0 mg/l BA + 0.5 mg/l gibberellic acid (GA3) in which 83.3% and 76.7% plantlet regeneration were noticed in RS and Co-1 respectively. Somatic embryos were encapsulated in various alginate and calcium chloride (CaCl2) solutions and were kept in different temperature regimes for varied periods. On regeneration medium, the encapsulated embryos germinated into plantlets; in 3% sodium alginate + 100 mM CaCl2, maximum plant regeneration (74.0% in RS and 70.6% in Co-1) was noted. The influence of low temperature on storage of synthetic seeds and their conversion into plantlets were also studied and we noted that the 4°C was the optimum temperature for synthetic seed conservation and plantlet regeneration compared to -20°C and 25oC temperature conditions.