A Review of Prang Besar's Quest of Improved

Hevea Planting Material*

M NAND

"Lovedale" - Jail Road, Talap, Cannanore 670 002, Kerala, South India  

The Planter, Vol. 72, No. 839, Feb 1996.

 

Preface

Here is a review of Prang Besar's search for improved planting material which will elucidate the key role played by Major Gough and Dr Chittendem. Written 40 years ago and sent to the Prang Besar Board by Harrisons and Crosfield, I received a personal letter from RO Jenkins the then Chairman thus:

"K.L. has forwarded to us a copy of your PB story from Gough to the present day. It is a most creditable piece of work on your part, factual and well-written. It will be read by all my colleagues on the Board and by Mr McInnes, our secretary with pleasure and interest. Full marks.

With best wishes"

I do not know whether this review written 40 years ago has any relevance now. But I am sending it as Prang Besar will soon be extinct, as it has come into prominence as the future administrative capital of the nation.

There may be people even among the present day planting community who do not realise the value of Prang Besar's contribution to the planting industry to which Major Gough and Dr Chittenden have put an indelible mark.

 

THE PIONEER

As centenarian Ridley is the accredited pioneer of the rubber industry in the East, so is Gough the pioneer of budgrafting rubber in Malaya. It was around 1921 that Gough opened up Prang Besar Estate, and a year later, made his first attempt to budgraft rubber on a commercial scale.

Rubber planters viewed this undertaking, a new departure from the conventional practice of planting seed, with pessimism. Gough in carrying out his programme got very little encouragement, even though he was assisted by the Department of Agri­culture and received valuable guidance from Dr Heusser of the AVROS Research Station, in Java.

He was the least perturbed by what others thought about his idea. By his courage and determination, he persuaded and convinced his colleagues, a group of ex-service men and fellow planters, of the advantages of budgrafting and managed to win them over risking their money, as it was then feared that the whole project would be a failure.

EARLY HISTORY

Gough foresaw the advantages of budgrafting rubber, and in 1921 he scanned over a million mature rubber trees growing in the district of Kajang, to select the best trees for use as bud-parents. Little was known about the "genetics" of rubber and his selection was based on yield and vegetative characters.

From these million trees, he selected 618 and made them into clones and employed them in planting up Prang Besar (in 1921). These clones were scattered on over 1 000 acres, to subject them to varying soil condi­tions and environment.

When these clones reached maturity, they were scrutinized for desirable qualities, from the practical planter's point of view, such as a straight round stem, smooth bark, well-developed and poised crown, etc. and, above all, yield. After selection from visual obser­vations on the above lines, only about 100 clones were considered suitable for testing for yield and they were test-tapped. As a result of this test-tapping and the additional experience and knowledge gained thereby, the clones were later reduced to a mere 30 in number which, after prolonged test, were further reduced to 16.

Not being quite sure of how the buddings would perform and as an insurance against their possible failure; Gough planned an initial stand of 200 trees per acre, interplanting selected seedlings and buddings in equal proportions.

The area came into tapping in 1927/28 and in 1934 the overall yield was 530 lb per acre per annum. This yield, even at the 1934 standard, could not be called surprisingly high but could be regarded as quite good. 

HARRISONS & CROSFIELD
COMES IN

Gough's embryonic selection work gave Harrisons & Crosfield the insight into the great possibilities, in developing the estate on other lines, than that of a commercial estate, producing and selling rubber; and when in 1926, the original Prang Besar Estate was bought by Sir Eric Macfadyen, for Harrisons & Crosfield, he directed that investigation and production of improved planting material, should be another vital object of the company. With the appointment of Dr R J Chittenden as geneticist in 1927, the idea took shape.

 

BREEDING WORK

Dr Chittenden started his breeding work in 1927, with the best of Gough's original selected valuable material. He used it in a series of diallel crosses, in his hand-pollination programme. Legitimate seedling families were thus raised and planted out commercially, for observation and testing. He purposely planted his hand-pollination plots at a reduced stand, as he did not contem­plate any thinning out, except by natural means; nor did he make any selection in the nursery. Every hand-pollinated seedling was used.

HAND-POLLINATION PLOTS

The first hand-pollination plot was planted in 1928 and thereafter, every year, small plots were added. The size of these plots depended on how many families were produced and the number of seedlings that could be raised. Prang Besar now possessed nearly 172 acres, planted with seedlings raised by hand‑pollination, in 22 plots, situated in different parts of the estate. Of these, 79 acres are pre‑war plantings and the remaining postwar ones.

About 8 acres of the latter are mature rubber which is under test and the balance of 85 acres contains rubber of varying ages, the oldest being about five years and the youngest only a few months.

The hand-pollinated plots (known as P. Plots on Prang Besar) P 1 to P 5, planted 1925/28, contained 39 legitimate families and the results of the first 29 months of experimental tapping of the families, on the S/2, d/2, 100 per cent system, is summarized and produced in the Planters Bulletin, No 11, March 1954. The mean yield in pounds per acre is shown as 1920.6 which could be considered very satisfactory.

During 1934/37 a further five P. Plots were established - P7, P8, P9A, P9B and P 10, P 7 was planted in 1934 and in its seventh year from planting, yielded an average of 70 lb per month.

The other P Plots were too young and the Japanese war prevented the areas being tested according to Prang Besar's schedule and actual test-tapping was started only some time after the re-occupation.

Dr Chittenden continued his breeding work after the re-occupation, mainly from Gough's original selection, which was augmented by his own selection and a few clones from neighbouring rubber growing countries, until his death on 6 December 1949. Where he had left, his successor Keiding continued the breeding and selection work.

 

PROVING OF CLONES

As a result of breeding and selection Dr Chittenden evolved a large number of newer clones, the better ones amounting to about 60. These clones were tested in two stages.
In the early stages of breeding and selection, all hand-pollination were made into clones, which were interplanted with one or more proved clones as control. This method, though advantageous, called for large acreages and in later years only the best hand-pollinations were selected for vegetative propagation. But, of late, this method has been reversed and the original method of making all seedlings of the different families into clones when big enough to be used as budparents, is in vogue. Thus the hand pollinated seedlings and the clones raised from them could be tested simultaneously, which means a saving of time in the proving of clones.

 

Preliminary Proof

The first stage of testing is preliminary proof. The selected hand-pollinated seedlings, after at least two years of test-tapping, and if found satisfactory, in respect of both yield and vegetative characters, are made into clones and planted out in the field under normal commercial conditions, each clone occupying 15/20 trees. The control, in most cases, is PB 86, a very reliable all round clone. The aim was to get at least 10 trees at the tapping stage, for testing. These preliminary proof areas received no favourable treatment and they are treated identically with other commercial areas on the estate.

The performance of these preliminary proof clones is carefully observed in regard to their growth, nature of the bark and other vegetative characters and most important of all, the yield. High yield and the most desirable characters are the important factors in selection. An awkward tree, however high the yield might be does not merit selection.

 

Further Proof

The second stage is further proof. After at least two years of test-tapping in the preliminary proof areas, clones which have yielded 25 per cent and more than the control and which have satisfactory vegetative characters, are picked out for further proof.

The further proof areas are laid out statistically in randomized and replicated blocks, each clone occupying roughly 1 acre. The control is nearly always PB 86, a highly reputed clone in the East and especially in a favourable habitat. No doubt, clones behave differently, under different environmental conditions.

The object of laying out the further proof areas statistically, is to ensure that the conclusions drawn are reliable and accurate. In any experiment with agricultural crops, our observations and conclusions might be influenced by several factors, some of which, like soil variation, are recognizable, while others are beyond our control. The latter would cause one to draw wrong conclusions. Randomization and replication allow the researcher to evaluate the degree of error in his observations and arrive at more reliable and accurate conclusions.

 

EXPERIMENTAL RESULTS

The Prang Besar, June 1941 circular, gives a list of 60 new clones tested and the results.

In the April 1948 circular are produced tapping results and a vegetative description of 70 preliminary proof clones and 20 further proof clones under test. Of these 70, Dr Chittenden recommended only a dozen for small-scale experimental planting.

By 1951, the further proof clones under test, dwindled to a mere 18, the less promising ones having been discarded for low yield and/or less desirable vegetative characters. In the same year, the preliminary proof clones under test fell to 32 from 70. It would be realized, that some of the clones are under­going both preliminary proof and further proof tests.

After continued selection of the better ones and rejection of the less desirables, Prang Besar, in their July 1955 circular, recommend only 11 clones, of which three are recom­mended for planting "in blocks of up to 25 acres"; the remaining eight in "blocks of 15 acres".

How rigorous is the selection and how careful their recommendation, can be judged from the above.

  

SEED GARDENS

Prang Besar's seed gardens C, D and E contain the best clones raised from the 39 families in P1 to P5. These gardens were initially planted, as polyclone plots of a speculative nature, the constituent clones in them, being those raised from Gough's original selection. These have produced valuable seedling progeny and buyers of C, D and E seed have been encouraged in its further use in sub­sequent plantings from the very satisfactory results obtained. 't

Seed from isolation gardens C, D and E was statistically tested in a 6× 6 Latin Square Experiment consisting of four-and-a-half acres randomized blocks against:

·                     Budded stumps in equal proportions of PB 186, 183 and 86

·                     Open pollinated seed of good quality

·                     Open pollinated seed of Prang Besar origin

·                     Plot C seed (isolation garden)

·                     Plot D seed (isolation garden)

·                     Plot E seed (isolation garden)

The tapping results were published in Prang Besar's June 1941 circular. The yield of C, D and E is bulked and shown as "yield of isolation garden seed plots". In all cases, in the experiment, the isolation garden seed plots have yielded more than any other type tested.

Encouraged by these results, Prang Besar recommended this material for large scale planting and the results show that the company has been justified in doing so and they can rightly be proud of their material.

They did not stop here. The search for still better planting material continued and a further two seed gardens F and G were opened up. The constituent clones in these gardens, are an improvement from those used in C, D and E and from theoretical consid­erations the progeny from these gardens, should be considered as an advancement on the previous gardens C, D and E.

The surest test to evaluate any planting material, is to plant out fairly large areas under commercial conditions, in different soil types and environmental conditions and see the results.

Sale of F and G seed commenced only after the re-occupation and such areas as have been planted post-war, have reached the bearing stage only fairly recently and there­fore tapping results are few. But the few results available (see Prang Besar, July 1955 circular) are encouraging and indicate that F and G seed are an improvement on C, D and E.

In their never ending and untiring quest for better and still better planting material, Prang Besar opened up a still newer seed garden, guided by their past knowledge and experience. This garden is named "Gough Garden" to commemorate the pioneer of budgrafting (in Malaya), who was the first to initiate selection work on Prang Besar. The seed from this garden is now marketed as Gough Garden seed.

Sale of Gough Garden seed commenced only a year ago and it is too early to pass any judgement about its value, until areas planted with this material come into tapping, which will not in any case be earlier than 1961. Nevertheless, the experience of more than 25 years of breeding and selection has gone into the composition and layout of this garden and it can be considered that Gough Garden progeny may be an improvement, on all seed types, so far marketed by Prang Besar.

All Prang Besar seed gardens aforesaid, are situated in Perak and each plot is adequately protected from each other, by large areas of coconuts. Apart from the seed gardens, there is no other rubber nearby, the extensive areas surrounding them being coconut estates.

  

PLANTING RECOMMENDATIONS

Under "Planting Recommendations, 1955/ 56", the Rubber Research Institute of Malaya (RRI) have classified, among others, PBIG seeds from isolation gardens C, D and E as Class I and recommended its use to the extent of 80 per cent of any replanting or new clearing. Obviously the RRI have to be extremely cautious in their recommendation, and they, in view of the fact that very little is known about the performance of F and G seed, under commercial and varied condi­tions, have graded this as Class II. Their planting recommendation of this material is "in the aggregate of 20 per cent of any new or replanting".

 

 

THE AIM

Broadly speaking, the aim of the plant breeder, is the improvement of the material he is dealing with. The methods he uses, depend on the type of material on which he is working. One of the methods, often used in the improvement of agricultural crops is inbreeding and crossing of the inbred lines.

In Hevea, this method is, from a commercial, point of view, thought less desirable. When inbred, there is the risk of Hevea losing vigour and yield. A high degree of heterozygosis is also thought probable. Inbreeding and improving Hevea may therefore require a large number - but how large has not been determined of generations before anything approaching a pure line could be obtained. Such an expensive and lengthy 'process should be left to the research worker.

The aim of an ordinary estate trying to produce improved planting material, in the hope of fair and quick returns for the money invested, will mainly be concentrated in producing high yielding families by crossing proved and promising clones. It is with this objective, that Prang Besar started their search, by interbreeding and selection and they have been encouraged by the results so far obtained. 

 

FUTURE PROSPECTS

It is a well-known and accepted fact that the planting industry in Malaya developed into its present state from about a few thousand seedlings introduced in the East, some 75 years ago. So much interbreeding would have, therefore, taken place by now, That it may be assumed the material available in the East is already homozygous to some extent and further breeding and selection with the existing material, therefore, may not produce phenomenal results.

But, with the introduction of new material from Brazil  (the RRI is reported to have some) and the wide range of material already developed in this country and other neigh­bouring rubber growing countries, the geneticist's scope is indeed great and it may be possible, in years to come, that there can be planting material, capable of producing more than a ton of rubber per acre per annum.

By carrying out hand-pollinations and testing the families thus produced, the plant breeder is able to evaluate the families and judge the value of clones as parents. With the discovery of newer clones, valuable as seed parents, isolation gardens could be established to produce improved seedling progeny.

As new and better clones supersede improved seedling material, selections from the latter and breeding from them, will give rise to still better clones and the process continues and the quest for more and more improved planting material is never ending.