Research, management partnership crucial to rapid growth of rubber industry

Dr. N. Yogaratnam, Consultant, National Instituteof Plantation Management

Sir Henry Wickham's removal of rubber tree seeds from their native Brazil to Kew Gardens and then to Sri Lanka is known.

We have seen the original seedlings in the botanic gardens of Sri Lanka and we know how the seeds from these trees and other trees as well were distributed throughout Ceylon, Indonesia, Malaysia, Thailand and India, and how beginning with the first tapping of such a tree (an original mother tree) in 1909 the rubber industry has advanced to a total production of about 8250mlnkg of natural rubber per year.

This has made possible the worldwide transition to rapid wheeled travel during the last 75 or so years.

The rapid development of the rubber industry has depended upon the application of two favourite sciences, agronomy and chemistry. Plant breeding and clonal selection and propagation were started by the Dutch before 1920 and brought to its highest level by The Rubber Research Institute during the years 1925 to date. Selection alone has resulted in an increase of between 8 and 6 fold in rubber productivity per hectare during the years 1940 to 2000.

Chemistry has made possible the processing of rubber into pure and purer rubber culminating in the technically specified rubber system of commercial presentation as early as in 1965.

History

The history of rubber can be divided into few eras, for convenience of discussion.

These are : pre 1876 : Discovery and recognition of rubber as a plant and rubber as a product of the wild rubber plant; 1876 to 1910 : Dissemination of the seeds and seedlings and beginning of the penetration of rubber from cultivated rubber trees into the rubber market, thus, stealing the rubber market away from rubber produced in nature, principally in Brazil and Colombia and from the Mexican guayule, which produced a substantial proportion of all rubber used in the United States until 1910; 1915 to 1940 : The era of plant breeding, agronomy and ever expanding productivity.

Breeders working in on clonal selection have advised that one should never plant a pure stand of one clone because there might be something wrong with that clone. "Let us mix 2 or 3 clones in the same stand on the chance that one will be productive".

We have come a long way since that era of plant selection and breeding. It was an extremely productive one even so, and laid the basis for our future rapid increases in rubber productivity.

The next era is that from 1945 to 1960 : Plant breeding, of course continued and produced even more productive clones. During this period the discovery of the path of rubber biogenesis was worked out in detail.

The initial steps of rubber biogenesis are identical to the stages in the path of biogenesis of our own steroid hormones, our own vitamin A and the carotenoids of plants. Finally, the era 1960 to date : The discovery of yield stimulation first by 2, 4D and copper sulphate and then the recognition that both of these agents work through causing production in the tree of ethylene and, thus, the discovery of ethylene as a yield stimulant.

Yield simulation works by prolonging the flow of rubber latex from the tree and thence exploitation of a greater portion of the trunk than is possible without use of the yield stimulant.

This period brought also the age of technically specified block rubber and the development of the Hevea crumb process. It also marked sociologically the emergence of the smallholder as a majority producer.

Increase out put

Let us now confine to two topics : The first is, what can be done to increase the output of natural rubber - the output of which our world needs, wants and indeed demands? This demand is projected to rise by 2-fold from today's 8250Mlnkg per year to double this amount by the early 2020. The second topic is, to what extent can technical innovation and improvement of the rubber plant and its crop management continue in the future as it has in the past?

The answer to the first question is simple. If all rubber hectares now in use were planted to high yielding clones and subjected to optimal crop management, production would be increased instantly, by at least 2-fold. If these measures were taken and ethylene also used optimally the increase would be about 4-fold.

Application of the knowledge we already have is all that is required to increase rubber production quite significantly. We realize that really applying today's knowledge is easy to call for but hard to do. It takes capital, replanting schemes, fertilizers, pesticides, saturating advisory service.

Nonetheless, rubber is economically such a profitable crop now and with such a bright long-term future that a great deal of application of present knowledge to the production and cultivation of rubber should happen in the next several years.

It would seem to be important that if the rubber industry of Sri Lanka implement application of all new knowledge, rubber could continue to be a major source of Sri Lanka's foreign exchange even surpassing Tea.

Innovations

The second question relates to what innovations in rubber practice can one foresee for the longer-range future? Classical plant breeding and selection have done an immense amount of good for Hevea. It may still do some good by way of conferring more disease and drought resistance, etc., upon our favourite plant.

The dwarfing root stock is an idea whose time has not yet come; although, there is an obvious need for such a root stock. Innovations in control of fungal diseases are quite advanced over a range of pathogens.

In many cases; the pathogen carries on its surface an elicitor which causes the host plant to produce a fungal toxin, called a phytoalexin.

In one case the nature of the elicitor is known and it can be synthesised readily since it is a simple disaccharide. The elicitor is a potent fungicide.

We know enough about the biochemistry of disease resistance to exploit it in great depth in the next few years and to be able to cope with such serious diseases of Oidium in Sri Lanka, and perhaps even South American Leaf Blight, should it ever invade our territory.

Harvesting

We know enough about the biochemistry of latex flow and latex flocculation to be able to control, that is, to lengthen latex flow to a considerable extent by ethylene treatment.

We will no doubt gain still more control over latex flow in future. As labour costs become more important as an item in the cost of rubber production we can still further increase the latex harvested per individual tapper per day.

For example, short cuts coupled with ethylene treatment can yield more runner per tree per tapper and still make it possible for the tapper to tap more trees than is possible by current procedures.

Devices to overcome shortage of skilled tappers have been evolved. With switching on to low intensity tapping with yield stimulation, the tapping frequency can be reduced to once in four days or even once a week is being attempted by other NR producers.

Crop recovery is higher by an average of about 30% and the workers also get corresponding higher wage incentive.

They may prefer once a week system as more blocks can be tapped in a week and obtain enhanced wages. This can to an extent solve the problem of tapper scarcity on estates as one worker will be able to cover more blocks compared to the once-in-two days or once-in-three days system.

This system also has the advantage in that it yields better and as the gap between two tappings is wide, the trees also remain healthier. The productivity life of the rubber trees may get extended to about 35 years in once a week tapping.

The tapping panel dryness would also be expected to be low or even absent in weekly tapping. The productivity linked incentive wage system would make the workers happy as they can earn more.

An intensive drive to popularise this in the small holding sector is considered useful, as it would solve their problem also to a great extent.

Application of the G-Flex system which is known to be the latest in the generation of gaseous stimulation technologies, is reported to be more cost - effective, easier to implement and user-friendly in harvesting latex, and us of which should be considered jointly by Research and Management.

Agronomy

One of the ways in which we can improve rubber yield per hectare per year is, of course, by better agronomy, that is, shortening the time in the field between the time of transplant of young buddings to the field and time of opening.

It has already been shown that the length of the immature period in the field can be shortened from the conventional 7 or 8 years to about 3 1/2 to 4 years by the use of advanced planting material and by the simple strategy of ensuring sufficient soil moisture when they are planted.

Molecular genetics

Nonetheless, it seems that we may well be coming to an end of the good things we can do for rubber by conventional genetics and biochemistry. There is, however, a new genetics called molecular genetics and a new biochemistry called molecular biology, whose application to plants have already begun. Indeed, the application to animals have also begun.

The new genetics starts with the knowledge that the genetic material of all plants and animals is DNA, gigantic long molecules made of 4 kinds of building blocks fastened together in linear array. It is in the order of the 4 kinds of building blocks that the genetic information is encoded.

We do not know the size of the Hevea genome, that is, we do not know how much DNA is contained in it; although, it would be found soon. There is much to do in this field as far as rubber is concerned. In any case, the DNA is divided into several pieces called chromosomes.

The DNA of each chromosome consists of sequential segments each about 1000 - 2000 building blocks long and called genes. Each gene codes for the production of a specific individual species of enzyme molecule.

Although all the same genes are contained in each cell of each and every kind of specialized cell, only a few genes express themselves in any particular kind of specialized cell.

For example, the genes for making the enzymes for making rubber are turned on and expressed only in the nuclei of the latex vessels and they are turned off in all other kinds of cells of the rubber tree.

The techniques of molecular biology have made it possible to isolate specific individual genes and to insert these genes into the chromosomes of hosts species quite different from those of the donor of the gene.

Molecular biology

Thus several groups in the U.K. and in the U.S. have isolated the genes responsible for nitrogen fixation in certain kinds of bacteria and transfer these to other kinds of bacteria.

It is not too much to hope for that it will be possible to remove the genes for nitrogen fixation from microorganisms and to insert these genes for nitrogen fixation into the genome of the rubber tree and thus make the rubber tree independent with respect to nitrogen supply.

We should expect that a major development in Hevea within the nest 5 -10 years will be the transfer of the genes for nitrogen fixation from, say, azotobactor to Hevea, thus freeing us from the need for nitrogenous fertilizer. Not doubt genes for specific kinds of disease resistance could be transferred from one species to another in this same roundabout way.

Nature has also arranged it so that all creatures are divided into species which cannot in general mate with one another. For example, the cross of human by mouse has not been recorded. On the level of the cell, however, anything goes.

Place human cells and mouse cells together in the same culture and they fuse and form cells containing all the genetic materials of human and of mouse. Such cells can multiply.

The same appears to be the case with plant cells. Cell fusion may provide us with another way to transfer the genes for nitrogen fixation or disease resistance from the required and desirable dommor to the recipient Hevea cells in tissue culture.

The new biology opens the door to a whole new world of agricultural development. Want a rubber tree that will thrive on low rainfall? Cross it with a pineapple which by virtue of its special mode of photosynthesis thrives on little water (about 1/10 as much water per unit of dry weight produced as is true of conventional crops).

We do not yet know and can hardly guess where our new found tools will take us and what we can do with them.

Latex protein allergy

Latex protein allergy of type 1 (immediate) hyper sensitivity has been emerging as a serious health related issue since the late eighties. Several techniques have been adopted to reduce the allergic potential of NR latex gloves though the production of low protein and powder-free gloves.

RRI Sri Lanka had reported as early as in 1997, that papain, a photolytic enzyme derived from papaya plants is useful in the production of deporteinised NR. More recent work in India has shown that control of proteins in surgical gloves by online wet gel and post-cure leaching is more effective with low protein latex produced using stablised liquid papain.

To summarise, that for the short range we can increase the production of rubber merely by doing the things we know how to do already - replanting our rubber hectares with high yielding clones, providing them with fertilizers and treating them with ethylene to maximise productivity per tree. In the longer run, we can make dwarf trees.

We can plant our trees under better conditions so that the time between planting and opening is lessened. In the still longer range we can create rubber trees which grow short and fat instead of skinny and tall ( put the energy into making productive bark rather than a very tall unproductive trunk).

And at the same time we can hope to make rubber trees that are more independent of outside resources and more dependent on their own internal resources; able to fix nitrogen, to repel fungi, and to produce more rubber at less cost.

All these indicate that we need to strengthen the link between research and management system in the country. This is one of the tasks before industry leaders and policy makers engaged in the country, one of the prime agro asset. Neither research nor management can function in isolation.