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Tree Genetics and Molecular Breeding, 2013, Vol.3, No.2, 4
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bottlenecks in tree improvement and seed production
have to be removed through improved basic research,
the potential of leading edge areas like biotechnology
must also be used for speedy improvement of this
plantation species. Since teak is a highly cross
pollinated species, one of the reasons for low fruit and
seed set and poor seed viability could be the low
genetic variability between the clones which are
assembled in clonal seed orchards. The natural crossing
between genetically similar or related genotypes may
be causing poor seed set because of self-incomp-
atibility and inbreeding depression. The most common
problem encountered in teak seed orchards in India is
the asynchrony of flowering among different clones
assembled in the orchard. Some clones flower at an
early age (e.g. 4~5 years) whereas some others flower
only after 10~15 years. Sometimes when a clone
belonging to one particular ecotype (e.g. dry/moist) is
included in a seed orchard established in an area of
another ecotype it may not flower at all for 40 years or
more. The review provides the the status and
importance of genetic diversity studies on Clonal seed
orchard rose by Kerala Forest Department during
1985 at Kulathupuzha in South Kerala.
2 Depletion of teak forests
During the past 50~100 years teak genetic resources
have been drastically distressed because of uncont-
rolled logging and mixing of germplasm. Habitat ruin
and disintegration have constrained the distribution of
species to undersized and secluded populations. Alth-
ough, comprehensive studies on genetic variability in
teak are limited, significant variation in quantitatively
inheritable characters have been reported in proven-
ances of natural populations from India, Thailand and
Laos (Kjaer, 1996).
3 Plus tree Selection
As a part of teak improvement programmes recognition
of plus trees from natural forests and plantations has
been carried out. A plus tree is a morphologically exc-
eptional individual combining a number of enviable
traits. The criteria adopted for the selection of plus
trees of teak, each dominant tree is compared with at
least 5 trees within a radius of 50 meters from the plus
tree. In order to determine the dominance of the plus
tree, a scoring system is adopted for characters like
height and girth at breast height of the tree, clear bole
height, straightness of stem, pattern of branching,
resistance to pests and diseases, and seed production.
4 Establishment of Seed Orchard
The grafts of selected plus trees were used to establish
seed orchards.
4.1 Collection of scion-wood
Scion wood for grafting was collected during the
month of February-April from the selected plus trees.
Small branches bearing suitable bud from the upper
one third of the tree crown were collected. Bud-wood
cuttings, 10~30 cm in length were prepared from these
branches. These were bundled together, wrapped in
polythene bags and transported to the grafting sites.
The cuttings remained viable for 2~3 days.
4.2 Preparation of stock for grafting
One or two year old teak stumps about 15~25 mm in
diameter at the collar region were used as stock for
grafting. Such seedlings were collected from the nursery
and stumps 15~20 cm long were prepared out of it.
4.3 Grafting technique
Though two types of grafting such as cleft grafting
and bud grafting have been experimented in teak the
latter was preferred because it ensures greater
economy of bud-wood material. Depending upon the
number of good buds on the bud-wood, it is possible
to make 3~5 grafts from a single bud-wood instead of
only one as in cleft grafting, it is easier and quicker
than cleft grafting, it suits for grafting on naked
stumps. Budding was done in the collar region of the
stump. A rectangular patch of the outerbark hearing
the bud was removed from scion-wood, An equal
sized bark was removed from the collar region of the
stump, and bark with the bud from the scion-wood
was fixed there and tied with polythene tape. The
upper cut-end of the stump was covered with wax.
Grafted stumps were then labelled and planted in
polythene containers (25×15 cm) filled with sieved
soil. The containers were kept under shade or a thatch.
Unwanted sprouts arising directly from the stump,
other than the affixed bud, were removed. Successful
grafts sprouted in 10~20 days giving out first pair of
leaves. Established buldlings were kept in the nursery