High-frequency clonal propagation, encapsulation of nodal segments for short-term storage and germplasm exchange of Ficus carica L.

Abstract

The study describes an efficient regeneration system and encapsulation of nodal segments in F. carica accompanied with frequent root formation in microshoots under the influence of salicylic acid. The present study describes an improved protocol for clonal propagation and a short-term conservation strategy using an encapsulation technology for Ficus carica. Nodal segments were more responsive than shoot tips for shoot multiplication. Among the cytokinins tested, Murashige and Skoog’s (MS) medium augmented with 7.5 µM 6-benzyladenine (BA) was the best, but the leaves exhibited a rudimentary structure. Cytokinin–auxin combinations enhanced the multiplication rate; but leaf growth did not improve. However, the supplementation of 50 µM adenine sulphate (Ads) to MS + 7.5 µM BA + 0.5 µM α-naphthalene acetic acid (NAA) significantly enhanced mean shoot number per explant and overall growth of shoots and induced a maximum of 26.8 shoots per nodal segment and 15 shoots per shoot tip with mean shoot length of 8 and 4.3 cm, respectively, after 4 weeks of culture. Microshoots rooted on half-strength MS medium containing 2.5 µM salicylic acid (SA) either in semi-solid (mean of 4.6 roots per shoot) or liquid medium (mean of 5 roots per shoot). A gelling matrix of 4 % sodium alginate (Na-alginate) and 100 mM calcium chloride (CaCl2·2H2O) was used for the encapsulation of nodal segments. Maximum shoot growth (95.6 %) was recorded on MS medium supplemented with 7.5 µM BA + 0.5 µM NAA + 50 µM Ads. Rooting was induced upon transfer of sprouted microshoots to semi-solid half-strength MS medium supplemented with 2.5 µM SA. To examine the retention of encapsulated and non-encapsulated nodal segments’ viability, a low-temperature storage (4 °C) experiment was carried out. Encapsulated nodal segments stored at 4 °C for 1–6 weeks sprouted at variable frequencies in successive weeks of transfer. Plantlets were acclimatized and established in field where they grew without any detectable variations after 6 months of transfer.