Cytomorphological studies in an induced polyploid of Hevea brasiliensis Muell. Arg.

Abstract

The Para rubber tree, Hevea brasiliensis Muell . Arg. belonging to the family Euphorbiaceae is the most important commercial source of natural rubber . The genus Hevea has nine species. Work on the cytogenetical aspects of the genus in general, and that of H. brasiliensis in particular, is rather meagre. Since the geneiic base of cultivated H. brasiliensis is limited, every effort has to be made to broaden the breeders' stock. An important method to cause genetic variability is the induc tion of polyploidy by artificial means and this technique has also been tried in Hevea (Shepherd 1969, Markose 1975, Zheng Xuequin et al. 1980. The Rubber Rese arch Institute of India has succeeded in inducing polyploidy in Hevea, by the appli cation of colchicine. This paper deals with the cytomorphological analysis of an induced polyploid in Hevea brasiliensis. Materials and methodsClone RRII 105, evolved by the Rubber Research Institute of India through hybridisation and selection with Tjir 1 and G1 1 as parents, was used for the present investigation. Plants raised in budwood multiplication nurseries were cut back and at the time of bud break they were swabbed with cotton. 0.75% aqueous colchicine was dropped on to these tender bud sprouts so that the cotton gets wet. The tre atment was continued daily for seven days. The shoot developing from the treated buds were regularly observed. The basal buds of those which showed morphologi cal variations were utilised for vegetative multiplication. Subsequent vegetative generations were also raised employing the basal buds of the respective shoots.Observations on morphological characters were recorded from one year old budgrafts of the VM 10* generation. Normal one year old budgrafts of RRII 105 were also observed for comparative purpose. Assessment of foliage characters was made from the middle leaflet of twenty selected leaves. Mitotic studies were made on tender leaf tips.Three year old budgrafts were ringbarked for early induction of flowering (Sa raswathy Amma 1975). For meiotic studies young male flowers at the appropriate stage of development were fixed in 1: 3 acetic alcohol mixture. Anther columns were dissected out and kept in 2% acetocarmine, overnight. Meiotic preparations * Vegetatively multiplicated 10th

Development of In vitro Tetraploid Plants of Hevea brasiliensis

“…by applying colchicine on the axillary buds started by 1984 [8]. Success obtained through this method was very low due to the chances of occurrence of chimeras and the difficulty in stabilizing the polyploids.…”

“…Callus induction from leaf explants of Dionaea muscipula different concentration of colchicines was attempted and they observed that callus induction rate decreased when colchicine concentration was high [10]. In the second treatment where colchicine was incorporated in the culture medium, there was no browning of the colchicine treated callus, instead the callus first turned white and watery and later, upon from colchicine treated calli buds started by 1984 [8]. Success obtained through this method was very low due to the chances of occurrence of chimeras and the difficulty in stabilizing the polyploids.…”