Abstract

For genetic improvement of planting stock of teak, clonal seed orchards were established in Kerala during 1979- 81 by bud grafting selected plus trees from different geographic origins. Even after 15 years of growth, flowering and seed production in most of the clones were not promising. It was suspected that lack of flowering may be due to any one or more of the following reasons. 1. Growth of root stock instead of scion during the establishment of grafts. 2. Stock - scion interaction 3. Nutritional imbalances. 4. Physiological reasons like hormonal inadequacy, insufficient light, temperature, moisture, etc. To find out the nature of flowering and seed production in existing clones, a study was undertaken in the seed orchard at Kalluvettamkuzhi, Arippa. Observations were recorded on nature of flowering, molecular characteristics of root and shoot DNA of 11 trees belonging to three plus trees, nutritional status and physiological parameters among flowered and non-flowered trees. The study revealed that the percentage of flowering varied from 2-3 in 1999 and 2000 which increased to 5 in 2001 and 2002. The phonological phase fruiting were spread over a period of seven months i.e., from June to December. The clones differed in flower production per inflorescence. The fruit production varied from 65g/tree to 300g/tree. The average fruit production was 125g/tree. Cluster analysis of RAPD data revealed five distinct clusters. Three plus trees stood separate from rametes and formed a distinct cluster. Flowered and non-flowered clones showed a tendency to group together into separate clusters. Two clusters each were obtained for flowered and non-flowered clones. With minor exceptions, the DNA from the scion of a clone clustered with the DNA from its stock. The results indicated that the stock and scion of a clone were highly similar at the DNA level and the scions did not evince any relation to the plus trees from which they were derived. In addition, the flowered and non-flowered clones were genetically distinct. Since the number of samples analysed was limited a definite conclusion could not be drawn from these results. No polymorphism could be found in isozyme analysis in the material collected from seed orchards also. The foliar nutrient contents N, P, K, Ca and Mg showed considerable variation within clones and between clones. There was a decrease in P and K contents in the leaves of trees flowered from the time of flowering till fruit maturation after which there was an initial increase, though not prominent. If a stress was given to the trees by giving more P and K at the time of flowering and very low N, Ca and Mg, to a certain extent the problem of poor flowering could be solved if all other conditions were conducive to flowering. Eco-physiological studies in the orchards showed that parameters like light, temperature or rainfall were not a limitation for seed production at Kalluvettamkuzhy. This may be due to the wider spacing (8x8m minimum) given while planting ramets in this orchard. The results obtained in the study points to the possibility of graft failure in the ramets and the low variability between the clones and ramets used in the study. Use of rooted cuttings of micropropagated plants and adopting a more favourable spacing in future clonal seed orchards is suggested.