Somatic embryogenesis and plant regeneration from the immature cotyledonary tissues of cultivated tea (Camellia sinensis (L).O. Kuntze)

Abstract

Embryogenic callus development, plant regeneration, and plant recovery were achieved from immature cotyledon explants of cultivated tea, when cultured on MS basal medium. The somatic embryo induction frequency was influenced when the medium was supplemented with 1 μM auxin (NAA, NOA, 2,4-D, TPB, and PBOA) in combination with cytokinin (0.5 μM BA, KIN) or 10% CM. The highest somatic embryo induction frequency was obtained using PBOA + BA or PBOA + KIN treatments. All auxins except 2,4-D stimulated rhizogenesis using 0.8% and l.5% agar concentrations, and differentiation of a characteristic swelling and friable callus from the exposed surface of the explant that remained nonembryogenic. Conversely, the novel auxins TPB and PBOA at 1 μM concentration with 3% or 6% agar, produced somatic embryo induction, while at 0.8% and 1.5% produced nonembryogenic callus. Explants isolated proximal to the zygotic embryonal axis showed a greater somatic embryo induction frequency than did the distal explants. The embryogenic competence was maintained through repetitive embryogenesis for a period of over 18 months. The somatic embryos developed into plantlets when incubated on hormone-free medium. The conversion frequency was increased by 50% in MS medium containing 1 μM Brassin and 0.8% agar. Concentration of agar at 3% and 6% decreased the conversion frequency and promoted anomalous plantlet development. The normal plantlets were treated with 1 μM IAN, 1 μM Brassin and 10 μ Phloroglucinol in liquid MS medium for 15 d, where profuse lateral roots were induced favoring a high rate of plant recovery.