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Subject: Floriculture and Landscaping × Author: Lavanya, R × End date: 2000 × Start date: 2000 × Type: Thesis ×
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    ThesisItemOpen Access
    Micropropagation and crop improvement of Cordyline (Cordyline terminalis (L.) Kunth)
    (Department of pomology and floriculture, College of horticulture,Vellanikkara, 2000) Lavanya, R; KAU; Rajeevan, P K
    Investigations on micropropagation and crop improvement of cordyline were carried out in the Department of Pomology and Floriculture, College of Horticulture, Vellanikkara during 1998-2000. The main objectives were to study the response of various explants and to identify the most suitable explant and media combination for in vitro propagation. Attempts were also made to find out the optimum dose of y - irradiation, for inducing variation. The shoot tips and nodal segments of cordyline were found to be ideal explants for the enhanced release of axillary buds and for indirect organogenesis. The best sterilization treatment was wiping with 70 per cent ethyl alcohol, followed by a dip in 0.1 per cent mercuric chloride for 18 min. for shoots, nodal segments and axillary buds. For leaf segments, treatment with 0.1 per cent mercuric chloride for ten minutes alone was enough. The nodal segment explants collected in the drier months, namely; January, March, November and December showed no contamination. Survival percentage was the highest in the months of November and December. The shoot tip explants showed least contamination when collected during August to April. Early release of buds (4.4 days after inoculation) and further growth of buds was better in MS medium supplemented with BAP 3.0 mg r'. Maximum shoot proliferation was observed in MS medium with 2.0 mg rI BAP. In the case of shoot tips MS medium having Kin 3.0 mg r' showed less time (5.5 days) for bud emergence. Maximum number of shoots (2.5) was also obtained when MS medium was supplemented with 3.0 mg rl KIN. MS medium supplemented with BAP in combination with NAA also proved better for culture establishment of nodal segments and shoot tips. Maximum number of shoots was observed in MS medium with NAA 0.5 mg r' + BAP 1.0 mg l". Of the different media tried, MS medium was found to be the best for early release of buds in nodal segments and shoot tips. Number of shoots produced did not differ significantly in all the three media. The elongated buds from Stage 1 showed very high rate of axillary bud production when inoculated in MS medium containing BAP 1.0 mg r' + NAA 0.5 mg r' and BAP 2.0 mg r' + NAA 0.5 mg r'. Among MS, SH and WPM media, full strength MS medium gave very high rate of axillary bud production within a short time (12.2 days). High rate of callus production was observed in MS medium having 1.0 mg r' BAP + 1.0 mg rl NAA and 2.0 mg rl BAP + 1.0 mg rl NAA. The rate of axillary bud production and callusing was less with KIN in combination with NAA. Irrespective of the media, rhizogenesis was observed when higher levels of 2ip was incorporated in to the media. Elongation of the multiple axillary buds with normal shoot and root growth was recorded in full strength MS medium devoid of growth regulators. None of the media supplements (activated charcoal, adenine sulphate, coconut water and casein hydrolysate) induced multiple axillary bud elongation. Among the three basal media tried, MS medium was superior with respect to the number of lengthy roots and the time taken for root initiation. Among the auxins, iliA was superior for root induction. Callus formation was observed at the base when NAA was incorporated in the media. Maximum percentage of rooting, early rooting and more number of lengthy roots were obtained in full strength MS basal medium. Addition of activated charcoal in the medium did not affect root number and root length, but reduced the number of days taken for root initiation. Triadimefon in the rooting medium slightly increased the number of days taken for root initiation and decreased the number of roots/culture and length of roots. It also increased the survival percentage during hardening. Maximum survival percentage of the plantlets was obtained when the plantlets rooted in the medium containing Triadimefon 1.0 mg r' + iliA 5.0 mg l' were treated with 0.1 per cent Bavistin for 30 minutes soon after removal from the culture vessels and subjected to a post planting treatment with triadimefon (20 mg rl) drenching at weekly intervals and kept in a net house having 50 per cent shade. Plant height was the maximum when the plantlets after planting out were supplied with 0.75 g 17: 17: 17 NPK mixture per week as soil drench. Among the various explants tried for somatic organogenesis, nodal segments and shoot tips were the most ideal for callus initiation, growth and differentiation. Callus intensity was maximum in the leaf segments when bottom portions of the immature leaves with midrib were cultured. Best response to callusing and callus intensity was obtained with the adaxial surface of the leaf touching the medium. Direct organogenesis could not be obtained in different treatment combinations or explants. Shoot tips and nodal segments produced higher percentage of callus and showed maximum callus index when MS medium was supplemented with lower levels of 2, 4 D (0.5 mg rl) and BAP (0.5 mg r'j, both in 12 h photoperiod. No positive response was observed with the addition of coconut water on callus induction and differentiation. Earliest differentiation of callus derived from nodal segment and shoot tip explants was possible in MS medium supplemented with BAP 1.0 mg r' + KIN 2.0 mg r': Very high rate of shoot production was observed in the medium supplemented with BAP 1.0 mg rl + KIN 2.0 mg r'. A combination of BAP + KIN gave high rate of shoot production, compared to BAP + 2ip combination. Various treatment combinations failed to induce morphogenesis in leaf derived callus, but additon of activated charcoal prevented browning of callus upon subculturing. Higher concentration of cytokinins prevented rhizogenesis. In vitro mutagenesis was attempted to know the optimum dose and correct stage for induction of variation. Of all the doses of y-irradiation, a dose of 10 Gy at culture establishment stage produced plants having narrow yellow leaves with green line at the centre, but after planting out the plantlets reverted to normal behaviour.