Protocols for Micropropagation of Woody Trees and Fruits

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V. RAJESWARI AND K. PALIWAL
than exotic species, they are well adapted to local climatic and edaphic condition
and enhance the naturalness of landscapes, and many produce premium quality
timber. In Sri Lanka, this species is popularly known as Ceylon rosewood and has
been identified as one of the important indigenous species for ex situ conservation.
This tree species has encountered genetic degeneration due to extensive felling of
phenotypically superior trees for commercial purposes. It is confined to a few natural
habitats and its natural regeneration is threatened. Hence, there is an important
need to protect the genetic resource of this species by establishing ex situ conservation
stands (Dominique, 1997).
Albizia odoratissima is commonly propagated through seeds. However, the
seeds are frequently infested by bruchids. The larvae of Bruchidius bilineatopygus
cause heavy damage to developing pods and seeds. Besides, wild stand seedlings are
highly variable in terms of growth and biomass production. More uniform, healthy
and vigorously growing planting stock of A. odoratissima that can benefit agroforestry
systems can be obtained from vegetatively propagated superior trees. For the
majority of tree species, propagation by rooted cuttings is often characterized by a
rapid loss of rooting capacity with increasing age of the mother plant (Biondi &
Thorpe, 1981). In many species, rooted branch cuttings tend to continue to grow
with a horizontal orientation and bilateral symmetry (plagiotropy) until the terminal
meristem changes to radial symmetry and vertical growth (orthotropy). This reversal
to normal growth displays frequent intra and inter clonal variation, and thus erratic
in selection program. Thus the evaluation of genotypes in a selection experiment
becomes almost impossible (Libby, 1974). Micropropagation technique could be
used as a complimentary approach for rapidly establishing a clonal orchard from
selected trees or control pollinated seeds from which further propagules will be
produced by rooted cuttings. In addition, tissue culture technique could be a viable
alternative to conventional vegetative propagation methods for mass multiplication,
tree improvement programs on superior canopy characteristics and resistance to
pests and diseases (Hossain, 1997).
In vitro regeneration has already been reported in Albizia odoratissima (Phukan &
Mitra, 1983). There are no other reports on in vitro propagation of this tree
species to the best of our knowledge. With an ultimate objective to establish a
method for clonal propagation of mature black siris tree, in the present investigation
initial studies were conducted with the seedling explants. This is primarily to generate
information on the nature of responses, exhibited in vitro by the tissues of this
plant, which can be extended to studies with mature explants. The plants raised from
tissue culture of seedling-derived explants will also be useful to confirm the
previous observations (Mascarenhas et al., 1987) regarding reduction of the juvenile
phase of seedling-raised tree.
2. EXPERIMENTAL PROTOCOL
The method developed for micropropagation of Albizia odoratissima using seedling
explants as well as two-year-old saplings is presented below.