Direct somatic embryogenesis with high frequency plantlet regeneration and successive cormlet production in saffron (Crocus sativus L.)

Abstract

Saffron is a slowly propagating geophyte with fungal infestation of corms under field conditions. Moreover, genetic improvement through breeding is not possible due to male sterility. Therefore, tissue culture methods offer a great potential for mass propagation, and somatic embryogenesis is one of the efficient methods. In the present study, direct somatic embryogenesis from leaf base was obtained in thidiazuron (TDZ, 2.5μM) and picloram (2.0μM) supplemented Murashige and Skoog medium (Murashige and Skoog, 1962). Significantly higher secondary embryogenesis was observed in embryo proliferation medium (EPM; MS supplemented with TDZ 2.5μM and picloram 1.0μM). The origin and different developmental stages of somatic embryos were ascertained through histological and scanning electron microscopic studies. Stomata were also observed in some of the somatic embryos. An alluring observation was retention of embryogenic potential beyond 3years of culture. Percent germination of secondary embryos in MS medium was 60.48 when matured in ½ EPM. Freshly initiated somatic embryos also germinated to form plantlets without undergoing secondary embryogenesis in MS medium containing TDZ (2.5μM) and picloram (1.0 and 2.0μM). Somatic embryo derived shoots were multiplied in 6-benzylaminopurine (BAP; 26.64μM) and α-naphthaleneacetic acid (NAA; 1.0μM). Growth performance of cormlets obtained from these shoots was evaluated under green house conditions. Somatic embryogenesis holds tremendous importance for mass propagation of saffron with formation of ultimate propagating material i.e., cormlets.