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Genetic Diversity and Canopy Management in Jack Fruit (Artocarpus heterophyllus Lam.)
Department of Pomology and Floriculture, College of Horticulture
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.