Standardization of Callus Induction and Shoot Regeneration in Twelve Species of Dioscorea

Abstract

Protocol was standardised for callus induction and shoot regeneration from leaf/stem/petiole/bulbil or root
explants in 12 species of Dioscorea namely Dioscorea bulbifera, D. pentaphylla, D. hispida, D. oppositifolia,
D. belophylla, D. wightii, D. spicata, D. intermedia, D. hamiltonii and D. pubera. While in 2 species no callus
could be induced. Type of explants as well as the type, concentrations and combinations of hormones used
influenced callus induction and regeneration. The most proliferative callus was obtained from leaf on MS + 2,4-D
(1-3 mg/l) in all the species. In D. intermedia, leaf explants cultured in MS medium with NAA (8 mg/l) and BA (2
mg/l) resulted in high callusing. 2,4-D in conjunction with BA in D. spicata and Kinetin in D. intermedia induced
callus. Distinct variation in colour and texture of callus was noticed. White friable/powdery callus was produced in
medium containing 2,4-D alone or in combination with BA. In D. wightii and D. belophylla, leaf explant in 2,4-D
(3 mg/l) produced brownish highly regenerative compact callus. 2,4-D derived callus gave the maximum callus
regeneration. In D. bulbifera and D. pentaphylla, callus regeneration occurred in MS basal medium itself, while,
addition of Kn (2 mg/l) was essential for shoot induction (1-3 shoots/callus) in five species. In D. belophylla 4
shoot buds regenerated in BA (4 mg/l). In D. hamiltonii TDZ (1 mg/l) gave a maximum of 22 shoots. Synergistic
effect of BA (2 mg/l) and Kn (1 mg/l) induced 6 shoots in D. bulbifera, 4 in D. hispida and 5 in D. wightii. Single
shoot was regenerated in D. belophylla in combination with BA and IBA, while Kn with IBA produced 2 shoots in
D. pentaphylla and 4 in D. hispida. A combination of BA and Kn along with NAA also resulted in shoot regeneration
in D. pentaphylla (2 shoots/callus), D. oppositifolia (2 shoots/callus) and D. intermedia (2-3 shoots/callus).