rubber cultivation

 

Propagation of Rubber

In India, Hevea seeds normally ripen during July-September when the seeds are collected and seedlings raised. All earlier plantations were raised from unselected seeds. The yield potential of these having been low, the production of those plantations was poor. Selection work on Hevea with a view to improving the planting materials and the introduction of vegetative propagation by budding led, in course of time, to the establishment of numerous valuable clones.

Nurseries

Nurseries are required for raising seedlings, budded stumps and budwood. As far as possible open and level land should be selected for raising nursery. Water should be easily available for irrigation. The soil should be deep, well drained and fertile. The land should be dug to a depth of 75 cm and all stumps, roots, and stones should be removed. Nursery beds should be prepared with 60 to 120 cm width and convenient lengths and with pathways laid in between to facilitate manuring, watering, weeding etc. Planting distances should vary according to the type of planting materials to be raised in the nursery. The ideal spacing for seedlings is 30 cm X 30 cm. For budwood nurseries, the plants may be at distances of 60 X 90 cm or 60 X 120 cm or 90 X 90 cm Nursery management aims at the most rapid production of standard healthy planting materials. More intensive care can be exercised in a nursery than in a field. Plants which are obviously unsuitable can be eliminated at an early stage. Mainframe operations for nursery include weeding, mulching, irrigation during dry months, manuring and disease and pest control.

Budding

The principle involved in budding is the replacement of the shoot system of a plant with that of another more desirable plant. In this process, a patch of bark of the seedling plant (stock) is replaced by a patch of bark with a dormant bud (bud patch) taken from the clone to be multiplied. The bud patch gets attached to the stock permanently and becomes a part of it. The stock is then cut off above the budded portion and the grafted bud develops into a shoot (scion) exhibiting the characters of the plant from which it was taken. The new tree thus formed is a two-part tree, comprising a root system belonging to the stock plant and a shoot system contributed by the donor of the bud. Depending on the colour and age of the buds as well as the age of the stock plants used, three types of buddings are mainly recognized. These are brown (conventional) budding, green budding and young budding. In the first method, older buds having brown colour are used while in the other two, green tender buds are utilised. Depending on the part of the stock where budding is carried out, buddings are classified into four types: base budding, crown budding, over budding and high budding. Base budding is carried out at the base of the stock plant and includes brown budding, green budding and young budding.    Tissue Culture Propagation of rubber is possible through tissue culture also. Tissue culture or micro propagation is the technique of producing plants from small (micro) pieces of plant tissues. Studies on tissue culture of rubber plants were started in 1966. Different parts of the plant such as embryo, anther, shoot tip and integument can be used for tissue culture. Rubber Research Institute of India has developed a technique for the production of tissue culture plants from shoot tips as well as somatic embryogenesis of different tissues. Rubber plants were developed by the somatic embryogenesis of anther tissue, integumental tissue, immature inflorecence etc. Attempts are being made for the tissue culture of other plant parts like leaf, floral buds, ovules and micro spores. Key steps in tissue culture of hevea include collection of the explant, sterilization, inoculation of the explant in a nutrient media supplemented with growth hormones and sucrose. The cultures were kept under optimum light and temperature conditions for the required period. Plants were formed in about eight months. They were then transferred to small polybags and kept in a green house for hardening. Even for the same clone the culture conditions vary with the physiological stage of the explant, seasons, part of the plant used etc. Because of these variations separate protocols have to be developed for each clone. This is a laborious and time-consuming process. However, procedures have been perfected for the propagation of several important clones by optimising these parameters. As in the case of most other tree crops, multiplication rate in tissue culture is very low for rubber. Further in the post-laboratory stages mortality is very high. However, after overcoming all these hurdles the RRII has successfully developed a large number of plants through various methods of tissue culture. These plants have been established in the field . Test tapping carried out on certain clones over their bud-grafted control and they are under different stages of evaluation.  Preparation and Packing of Propagation Materials The propagation materials handled by rubber growers are ungerminated seeds, germinated seeds, seedling stumps, brown budwood, green bud shoot, brown budded stumps, green budded stumps, polybag plants and stumped buddings. Specific techniques are required for the preparation of these materials.  If not properly prepared, their quality could be reduced, which in turn adversely affects the establishment after planting. After preparation, these materials may require storing and/or transportation. During storage and transit they are likely to get damaged by loss of moisture or by breaking, rubbing, bruising, crushing, etc. To avoid these and to give ample protection to these materials, certain specific methods are adopted for packing and transporting.  Climatic Conditions for Optimum Growth of Rubber Tree Rainfall of 2000 to 3000 mm evenly distributed without any marked dry season and with 125 to 150 rainy days per annum Maximum temperature of about 29oC to 34oC and minimum of about 20oC or more with a monthly mean of 25 to 28oC High atmospheric humidity of the order of 80% Bright sunshine amounting to about 2000 h per annum at the rate of 6 h per day through all the months Absence of strong windsOnly a few regions in India meet all these requirements.  Fortunately rubber can be grown successfully under moderately deviating conditions to  Types of Nursery Planting materials for establishing rubber plantations are generated in seedling, budwood and polybag nurseries. Selection of Site  Land Preparation In India, rubber plantations are established in forest clearings, rubber replantings or by crop replacement. Most of the areas available for rubber cultivation are highly undulating and the extent of flat lands suitable for planting rubber is limited. These situations necessitate clearing of the land and adoption of proper soil conservation measures before planting rubber. Since June-July is the ideal period for planting rubber in South India, all the pre-planting operations should be completed before the onset of monsoon.     f ield Planting The success of planting depends on the prevailing weather conditions, quality of the planting materials used and the care with which the planting operation is done. Continuous wet weather can be expected during June-July in the major rubber growing areas in India and hence this period is considered to be ideal for planting rubber. The actual method of planting will depend on the materials used for planting. Different types of planting materials used are seeds, seedling stumps, budded stumps and polybag plants.  Of these, the last two are the most common ones.