Direct somatic embryogenesis from mature zygotic embryo and conversion to plants in medicinal tree Terminalia chebula Retz. (Special Issue: Tree micropropagation and tissue culture.)

摘要

Terminalia chebula Retz. mature zygotic embryo (MZE) explants were evaluated for induction of direct somatic embryogenesis on Murashige and Skoog medium (MS) supplemented with 3% (w/v) sucrose, various combinations and concentrations of 2,4 dichlorophenoxy acetic acid (2,4-D) and kinetin (Kn). Seeds of T. chebula collected from different geographic and climatic zones such as Srisailam Tiger Forest Reserve, Srisailam, Andhra Pradesh, forest area in eastern part of Mayurbhanj district of Orissa and Ananthagiri Hill forest area, Vikarabad, Andhra Pradesh, India. Seeds of geographic zone in Mayurbhanj district of Orissa showed maximum frequency of direct somatic embryo induction (62.00+or-1.15 fully developed somatic embryos per explants) and was obtained on MS medium containing 1.0 mg/l 2,4-D and 0.01 mg/l Kn after 6 weeks of culture. The influence of seed age (duration after collection) as MZE source on direct somatic embryogenesis revealed that one-month old MZEs promoted maximum frequency; however, this declined with an increase in age. Somatic embryo maturation was obtained on MS media supplemented with 50 g/l sucrose. Direct and indirect (via intervening callus phase) somatic embryogenesis was a parallel process. A maximum of 26.33+or-1.20 explants showed direct somatic embryogenesis compared to 80.0+or-2.33 indirect somatic embryogenesis. Direct somatic embryogenesis can be advantageous in terms of curtailing more than four weeks of culture passage in vitro compared to indirect somatic embryogenesis. Conversion of somatic embryos to plants was possible on 1/2-strength MS medium fortified with 0.5 mg/l BA (6-benzyladenine) and 30 g/l (w/v) sucrose. Direct somatic embryogenesis and the conversion of somatic embryos to plants is reported for the first time in T. chebula.