PhD

The present investigations on genetic diversity and canopy management in
jack fruit (Artocarpus heterophyllus Lam.) was undertaken in the Department of
Pomology and Floriculture, College of Horticulture, Vellanikkara, during 1998 to
2002. Major objectives of the study were to explore the variability in vegetative,
floral, fruiting and biochemical characters of jackfruit through a comprehensive survey
in four different topographical regions of Thrissur district, namely, plains, hills,
coastal and riverside areas and to .select quality types, to ascertain the optimum degree
and frequency of canopy manipulation and to characterize the firm and soft fleshed
types through morphological observations, anatomical and biochemical analysis.
Variation was noticed with respect to tree vigour (low, medium and high),
canopy shape (pyramidal, broadly pyramidal, obovate, oblong, semi-circular, elliptical
and irregular), tree growth habit (erect, horizontal and drooping), branching density
(low, intermediate and high) and branching pattern (erect, opposite, verticiliate,
horizontal and irregular).
A wide variation was noticed in all the four topographical levels with
respect to leaf characters like length, width, length / width ratio, shape, apex shape and
base shape.
Surveyed accessions were grouped into three based on flowering and
bearing season, namely, (1) early flowering (September-October) and bearing
(December-February), (2) mid-season flowering (November-January) and bearing
(March-Mary) and (3) late flowering (February-March) and bearing (June-August), A
sporadic flowering and bearing type was also spotted.
Variation was noticed with respect to fruit shape (broadly ellipsoid, oblong,
high spheroid, spheroid, ellipsoid, obloid, clavate and irregular), junction of stalk
attachment (depressed, inflatened and flatened), fruit rind colour (greenish, greenish
brown and greenish yellow), shape of spines (sharp pointed, intermediate and flat),






intensity of latex exudation (low, medium and high) and flake shape (cordate, twisted,
spheroid, elongated-obovate, rectangular, oblong with curved tip and irregular).
Wide variation was noticed in terms of biometric characters of fruit. The
length of the fruits varied from 18.50 to 80.30 cm; girth 30.12 to 110.00 cm; fruit
weight 1.05 to 22.30 kg; fruit rind weight 0.30 to 4.26 kg; fruit rind thickness 0.28 to
3.93 cm; number of flakes 1.00 to 456.00; weight of flakes per fruit 0.51 to 8.21 kg;
weight of fresh flake with seed 7.15 to 63.50 g; weight of fresh flake without seed 5.36
to 46.4 g; flake fruit ratio 0.69 to 4.30; flake length 3.15 to 13.68 cm; flake girth 4.25
to 13.95 cm; flake thickness 0.1 to 0.4 cm; rachis length 13.5 to 63.58 ern: rachis
diameter 3.55 to 12.83 cm; perigone weight 0.43 to 4.16 kg and peduncle weight 0.21
to 2.93 kg.
Significant variation was noticed with respect to biochemical characters of
fruit like total sugar (8.16 to 19.30%), reducing sugar (1.63 to 5.23%), non reducing
sugar (5.96 to 14.98%), total soluble solids (14.63 to 33.00oBrix), total acidity (0.69 to
4.95%) and sugar acid ratio (2.32 to 20.81 %). The jack collections had widely varied
sensory attributes of flakes like appearance, colour, firmness, flavour, sweetness and
overall acceptability.
Seed characters like shape, surface pattern, length, girth and hundred seed
weight showed wide variation among the accessions.
Surveyed accessions showed wide variation regarding yield per tree ( 21.23
to 1710.00 kg) and number of fruits per tree (3.60 to 230.60).
Significant correlation was noticed between the biometric characters of
fruits like length, diameter, etc. Path analysis revealed that fruit length, fruit weight,
seed length and fruit number had direct effect on yield. Non-hierarchical eucleadian
cluster analysis revealed the existence of genetic diversity in jack. 80 collections in
each topography could be grouped into ten clusters.

Nine firm fleshed accessions namely AC-7, 224, 306 and 307 from plains,
AC-254 and 285 from the river side, AC-I02 and 293 from the coastal regions and
AC-203 from the hilly tract were selected.
Pruning trials in jack trees resulted in reduction in number of days taken for
flushing and flowering with decreasing order 0'1' severity. On pruned trees more
number of shoots with increased vigour was emerging with increasing severity of
pruning. No significant difference in duration of male and female spike development,
flowering and fruiting span was noticed among various pruning treatments. However,
all the pruning treatments showed reduction in span of flowering and fruiting.
All the pruning treatments showed enhanced percent of fruit set during first
and second year of pruning. Medium pruned trees showed maximum increase in fruit
set (3-6%) than severe (1-2%) and light pruned trees (2-3%).
During first year of pruning all the pruning treatments showed reduction in
fruit number and yield and the reduction was increasing with increasing severity of
pruning. In the second and third year of pruning, an increase in fruit number and yield
was observed.
No significant difference was noticed in total sugar, reducing sugars and
non-reducing sugars of flakes. However, in severely pruned trees, a slight increase in
the sugar content was noticed.
There were no significant differences between soft and firm fleshed types
in terms of morphological, anatomical and biochemical characters studied.