Optimization of in vitro bud induction and plantlet formation from mature embryos of Aleppo pine (Pinus halepensis Mill.) |
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Authors: | Maurizio Lambardi Kiran K Sharma Trevor A Thorpe |
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Institution: | (1) Present address: Consiglio Nazionale delle Ricerche, Instituto sulla Propagazione delle Specie Legnose, via Ponte di Formicola 76, 50018 Scandicci, Italy;(2) Present address: Legumes Cell Biology Unit, International Crops Research Institute for the Semi-Arid Tropics, 502 324 Patancheur, Andhra Pradesh, India;(3) Plant Physiology Research Group, Department of Biological Sciences, University of Calgary, T2N 1N4 Calgary, Alberta, Canada |
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Abstract: | Studies were undertaken to optimize tissue culture conditions for micropropagation of Aleppo pine (Pinus halepensis Mill.) from mature embryos and various explants of the embryo. Over 90% of the embryo explants gave rise to adventitious
buds within 4 wk. Intact embryos were the most suitable explants for shoot bud induction. Both isolated cotyledons and hypocotyls
produced adventitious buds, but these developed slowly and failed to elongate. N6-Benzyladenine (BA) alone at 5.0μM was the most effective cytokinin when added to gelled to gelled von Arnold and Eriksson’s (AE) medium containing 3% sucrose.
Adventitious bud development was achieved on hormone-free AE medium, and shoot elongation was optimum on three quarter-strength
Bornman’s MCM medium, with 0.1% conifer-derived activated charcoal. Shoots were multiplied on three-quarter strength MCM medium,
containing 5μM BA. To induce adventitious roots on the elongated shoots, pulse treatment with 1 mM IBA for 6 h, followed by the transfer of the shoots to sterile peat:vermiculite (1:1) mixture, was beneficial. After acclimatization
for 3 to 4 wk under mist, almost all the rooted shoots could be transplanted successfully to the greenhouse, where the plants
exhibited normal growth habit. Histologic studies on the ontogeny of adventitious shoot formation from mature embryo explants
revealed temporal structural changes in different parts of the explant. Induction of mitotic divisions on the shoot-forming
medium resulted in the formation of meristemoids in the epidermal and subepidermal layers of the explant, located initially
at both the tips of the cotyledons and the axils of adjacent cotyledons. Shoot buds arising in the axils of adjacent cotyledons
were due to new cell division and not to any preexisting meristem. |
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Keywords: | Pinus halepensis Aleppo pine micropropagation organogenesis shoot formation rhizogenesis |
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