Crop Management Unit

The Crop Management Unit (CMU) formulates its research programme with the vision towards achieving a modern and productive natural rubber industry in Malaysia through implementation of appropriate crop management technologies. To realise this, CMU will endeavour to generate technologies to achieve sustainable production of rubber by optimising land use through integrated farming and agroforestry, implementation of practical technologies of exploitation and appropriate agricultural practices. The major research areas undertaken are agronomy, exploitation techniques, integrated farming, agroforestry and laboratory automation techniques.

Research Highlights

Low Intensity Tapping systems

In response to the issue of labour shortage and increasing rubber production, the Rubber Research Institute has made great strides in developing technologies to obtain high yields and ensure sustainable production. Low Intensity Tapping Systems (LITS) were developed and found to be effective in overcoming critical constraints currently faced by the NR industry. LITS essentially comprise of technologies that employ low frequency tapping namely; LIT d/6, RRIMFLOW (RF) and REACTORRIM (RR).

The LIT d/6 system is a combination of a conventional half spiral tapping cut (1/2S) with reduced frequency of tapping (d/6), and stimulated monthly with ethephon. Ethephon stimulation is the most critical component in this system.

RRIMFLOW is a method of stimulation using a concept of intermittent gassing of the laticiferous tissues and combined with short-cut tapping of 1/8 spiral with lower frequencies of d/4 (once every 4 days).

REACTORRIM is a method of stimulation whereby a continuous but slow release of gaseous stimulant is applied to the laticiferous tissues of the Hevea tree, and combined with short-cut tapping of 1/8 spiral with d/4 frequencies.

The conventional LIT d/6 system is particularly workable for a smallholder with uneconomic size holding. The system allows the tapper greater flexibility in sourcing income from other activities since the tapping is done every six days only.

Higher range of yields were obtained with the novel systems (RF and RR). The efficacy of the RRIMFLOW and REACTORRIM techniques leads to higher land and labour productivity and in general improved income to tappers and smallholders as well as better profits to the estates.

In-Field Crop Collection

Due to the sharp increase in yield obtained with LITS it is necessary to devise an apparatus that can assist in-field collection of latex and coagulum rubber. The Crop Management Unit has recently produced several prototypes of the trolley cart "LANCA-GM’. Research on its usage has indicated that the cart could reduce fatigue of the worker and save one hour of collection time per task. Furthermore, with a maximum load capacity of 100 kg., it can be attached to a motorbike for transport to a collection point. The LANCA-GM is of practical use on flat to undulating terrain and work is underway to refine its use on terraces in hilly areas. 

Services

The analytical laboratory of CMU offers a wide range of services for the rubber industry. The laboratory is recognised nationally and internationally for its active involvement in cross-check studies and its long experience in soils and tissue analysis. The services offered are:

• Soil analysis
• Plant analysis
• Fertiliser analysis
• Water and sludge analysis
• CHNOS analysis

Other Research Activities

The other major areas of expertise at the Crop Management Unit are:

• Fertiliser use and rubber planting
• Mixed cropping of rubber and cash crops
• Development of rubber forest plantation
• Reduction of immaturity period of rubber
• Soil survey, soil and water conservation

Contact Person

Dr Mohd Nasaruddin Mohd Aris
Head of Crop Management Unit

Crop Improvement and Protection Unit

Natural rubber is produced by the rubber trees Hevea brasiliensis. The latex yield of the wild rubber trees is low and therefore is uneconomical to commercially cultivate. It is the obligation of the Crop Improvement and Protection Unit (CIPU) to produce new rubber clones with increasing latex yield. The Unit strives to achieve the objective by diligently carrying out breeding and selection programmes. New rubber progenies are produced by carrying out hand pollination annually. The rubber progenies are subjected to rigorous evaluation and various selection trials in the nurseries, small scale trials, block planting or large scale trials. The clones are selected for high latex and timber yield, vigorous growth, good tree morphology, resistance to wind, diseases and brown bast, and other secondary characters such as thick bark. The current targets of the breeding programmes is to produce clones which can produce more than 3500 kg/ha of latex and also yield more than 1.5 cubic meter of total rubberwood/tree. The Unit maintains a wide collection of rubber genetic resources for its breeding programmes.

Loss of crop occurs when the rubber plants are infected by diseases which defoliate or kill the trees. This Unit develops methods and procedures to manage every economically important disease of rubber. These procedures take into account reduction in cost of treatment, labour requirement and environment contamination. The Unit also screen new clones for resistance to diseases and monitor clonal performance against diseases in the field. CIPU also conducts research on weed control especially to develop cost effective environment friendly procedures to manage weeds in the rubber holdings.

Services provided

• Expert consultation on rubber breeding, planting recommendation, management of rubber diseases and weeds, and nursery operations.
  
  
• Accurate identification of common rubber clones and diagnosis of rubber diseases.
  
  
• Supply of rubber planting materials (budwood or plants in polythene bags) on orders.
  
  
• Technical evaluation on effectiveness of fungicides on rubber pathogens, and weedicides.

Contact person

Dr Masahuling Benong
Head of Crop Improvement and Protection Unit

Biotechnology

Scope of research

Research undertaken in the Biotechnology Unit covers the areas of tissue culture and genetic transformation, molecular markers and genetics, plant physiology, biochemistry and molecular biology, reproductive biology and latex allergy. While these areas encompass the basic and strategic biological research activities undertaken on Hevea at the Institute, a significant portion of the unit’s research has been structured to address specific needs of the rubber industry.

Image has been scaled down. See full-size image
Electron micrograph of a longitudinal section of a mature latex vessel. RP=rubber particle; L=lutoid; FW=Frey-Wyssling particle; LVW=latex vessel wall. Scale bar=1 µm.
Senior research staff
Azlina Bahari M.Sc.	abahari@lgm.gov.my
Badrul Ezam Badaruddin B.Sc. (Hons)	ezam@lgm.gov.my
Chow Keng See Ph.D.	kschow@lgm.gov.my
Nor Azreen Abd Rahman B.Sc. (Hons)	norazreen@lgm.gov.my
Nor Mayati Che Husin M. Sc. (on study leave)	normayati@lgm.gov.my
Roslinda Sajari M.Sc. (On study leave)	roslinda@lgm.gov.my
Safiah Atan M.Sc.	safiah@lgm.gov.my
Siti Shuhada Shuib B.Sc. (Hons)	shuhada@lgm.gov.my
E. Sunderasan Ph.D.	sunderasan@lgm.gov.my
Siti Arija Mad Arif Ph.D. (Head of Unit)	sitiarija@lgm.gov.my

Major research activities

Tissue culture and genetic transformation

The technique of tissue culture is being harnessed to meet the needs of genetic transformation of Hevea brasiliensis. Genes encoding for proteins that confer particular traits to the rubber tree are inserted into in vitro cultured anther callus tissue, the process being aided by a bacterium (Agrobacterium). The genetically transformed callus is subsequently regenerated into a complete plantlet though tissue culture.

An important objective of genetic transformation is the enhancement of crop productivity by improving selected agronomic traits of the rubber tree. Two characteristics of the rubber tree that could benefit from transgenesis are in girth increment for timber production and in resistance to diseases, particularly Corynespora leaf disease.

A second role for the transgenic rubber tree lies in the production of commercially valuable proteins in the latex. Genes encoding proteins of commercial value are inserted into rubber trees that then become natural "factories" for the production of the foreign protein. Examples of such proteins are pharmaceuticals and proteins used in personal care products. Foreign (recombinant) proteins synthesised in the latex in this manner are extracted continually and non-destructively by tapping the tree. Transgenic rubber trees require low maintenance and are environment-friendly as compared with bioreactor systems by which many pharmaceuticals are currently being manufactured. Experimental transgenic rubber trees at the Rubber Research Institute of Malaysia have successfully produced a bacterial enzyme (GUS), a mouse antibody and human serum albumin.

[Click here] More about the transgenic rubber tree as a living factory for the production of valuable proteins.

An aspect of genetic transformation under active research concerns the use of endogenous Hevea gene promoters (sequences of DNA which drive gene action) that function in specific tissues of the transgenic rubber tree. One promising candidate promoter for latex vessel-specific expression is the hevein gene promoter. (Hevein is one of the most abundant proteins in latex.) In a study, the DNA of the gus protein was linked to hevein promoters and used in Hevea genetic transformation. GUS expression was observed in the embryoids that were obtained.

The transgenic rubber plant	.
	Blue colouration of the latex (left) from the transformed plant after reacting with the GUS substrate. Latex from the control untransformed plant remains uncoloured.

Publications

YEANG, H.Y., AROKIARAJ, P., JAAFAR, H., ARIF, S.A.M., RAJAMANIKAM, S., CHAN, J.L., SHARIB, J., LEELAVATHY, R., HAMZAH, S. and VAN DER LOGT, C.P.E. (2002) Expression of a functional recombinant antibody fragment in the latex of transgenic Hevea brasiliensis. Journal of Rubber Research, 5(4), 215-25.

AROKIARAJ, P., RUEKER, F, OBERMAYR, E., SHAMSUL BAHRI, A.R., HAFSAH JAAFAR, CARTER, D.C. and YEANG, H.Y. (2002) Expression of human serum albumin in transgenic Hevea brasiliensis. Journal of Rubber Research, 5(3), 157-66.

AROKIARAJ, P., YEANG, H.Y., CHEONG, K.F., SAMSIDAR HAMZAH, JONES, H. AND COOMBER, S. and CHARLWOOD, B.V. (1998) CaMV 35S promoter directs ß-glucuronidase (GUS) expression in the laticiferous system of transgenic Hevea brasiliensis (rubber tree). Plant Cell Reports, 17, 621-5.

AROKIARAJ, P., JONES, H., HAFSAH JAAFAR, COOMBER, S. and CHARLWOOD, B.V. (1996) Agrobacterium-mediated transformation of Hevea anther calli and their regeneration into plantlets. Journal of Natural Rubber Research, 11(2), 77-86.

Molecular markers and genetics

Molecular markers serve as useful aids in understanding the genetics of Hevea brasiliensis. They can play a useful role in genotype selection and can hence facilitate and hasten the progress in Hevea breeding.

DNA probes and markers are being used for genetic and physical mapping, fingerprinting and detection of somaclonal variation. Currently, emphasis is directed towards the use of Amplified Fragment Length Polymorphism (AFLP) for mapping quantitative trait loci (QTLs), genetic linkage map construction and genotyping rubber cultivars with promising traits/characters for latex-timber production.

Publications

SAFIAH ATAN and NOOR HISHAM HAMID (2003) Differentiating races of Corynespora cassiicola using RAPD and internal transcribed spacer markers. Journal of Rubber Research, 6(1), 58-64.

LEITCH, A.R., LIM,Y.K., LEITCH, I.J., O’NEILL, M., CHYE, M.L. and LOW, F.C.(1998) Molecular cytogenetic studies in rubber Hevea brasiliensis L. (Euphorbiaceae). Genome 41, 464-7.

YEANG, H.Y., SUNDERASAN, E., WICKNESWARI, R., NAPI, D. and ZAMRI, A.S.M. (1998) Genetic relatedness and identities of cultivated Hevea clones determined by isozymes. Journal of Rubber Research, 1(1), 35-47.

LOW, F.C., SAFIAH ATAN, HAFSAH JAAFAR and TAN, H. (1996) Recent advances in the development of molecular markers for Hevea studies. Journal of Natural Rubber Research, 11(1), 32-44.

SAFIAH ATAN, LOW, F.C. and SALEH, N..M. (1996) Construction of a microsatellite-enriched library from Hevea brasiliensis. Journal of Natural Rubber Research, 11(4), 247-55.

Plant physiology, biochemistry and molecular biology

In studying Hevea biochemistry and its regulation at the whole tree and cellular levels, particular focus is given to the mechanisms that control the production of rubber. The molecular, biochemical and cellular aspects of key enzymes regulating rubber biosynthesis are being elucidated. Much of the recent work was centred on the role of proteinaceous stimulators and inhibitors in influencing the rate of rubber biosynthesis. Studies are also undertaken on the isolation, expression and characterisation of ethylene signaling pathway genes. Such genes could be important in the physiological regulation of latex flow when the rubber tree is tapped.

Another research topic receiving attention is in the area of Expressed Sequence Tags (ESTs). Short sequences of DNA isolated from the latex give a broad representation of the genes that are expressed in the latex. Genes of interest in future research could be isolated using these tags as guide gene sequences. The catalogue of genes would hence be valuable in studies on gene function and genetic regulation of Hevea physiology and biochemistry. As an example, a gene sequence coding for the enzyme of the first step of the purported alternative rubber biosynthesis pathway was identified from the MRB latex EST collection and a study on this gene is ongoing.

Publications

SUNDERASAN, E., LING, S.K., SITI ARIJA MAD ARIF AND YEANG, H.Y. (2007) Deciphering Rubber Particle Destabilisation by Hevea Bark Extract. J Rubb Res 10(2) 89-98.

CHOW, K.S., WAN, K.L., ISA, M.N.M., BAHARI, A., TAN, S.H., HARIKRISHNA, K. AND YEANG, H.Y. (2007) Insights into rubber biosynthesis from transcriptome analysis of Hevea brasiliensis latex. J. Exp. Bot. 58(10): 2429–2440.

KENG-SEE CHOW, FARIDAH YUSOF, SALIMAH MOHD. LIM AND LATIFAH ABDULLAH (2006). An Assessment of Stimulation of Hevea brasiliensis Rubber Biosynthesis by eIF-5A Protein-enriched Bacterial Lysates. Journal of Rubber Research 9(4): 251-259.

AROKIARAJ, P. AND YEANG H.Y. (2006) Yield stimulation of the rubber tree (RRIM 600) with Ethephon does not increase Latex Hev b6 Protein or mRNA. Journal of Rubber Research 9(1), 61-71.

PUJADE-RENAUD, V., SANIER, C., CAMBILLAU, L., PAPPUSAMY, A., JONES, H., RUENGSRI, N., CHRESTIN, H., THARREAU, D., MONTORO, P. AND NARANGAJAVANA, J. (2005) Molecular characterisation of new members of the Hevea brasiliensis hevein multigene family and analysis of their promoter region in rice. Biochimica et Biophysica Acta,1727(3),151-61.

YEANG, H.Y. (2005) The kinetics of latex flow from the rubber tree in relation to latex vessel plugging and turgor pressure. Journal of Rubber Research, 8(3), 160-81

KO, J.H., CHOW, K.S. and HAN, K.H. (2003) Transcriptome analysis reveals novel features of the molecular events occurring in the laticifers of Hevea brasiliensis (para rubber tree). Plant Molecular Biology, 53(4), 479-92.

K.-S. CHOW, SALIMAH M. LIM and K.-H. HAN (2003) Characterisation of a family of eIF-5A cDNAs from Hevea brasiliensis. Journal of Rubber Research, 6(2), 107-120.

SUNDERASAN, E., WARD, M.A. and YEANG, H.Y. (2002) Isolation and characterisation of latex cyanogenic glucosidase. Journal of Rubber Research, 5(4), 244-52.

SIVAKUMARAN, S., GHANDIMATHI, H., ZAINAB HAMZAH, FARIDAH YUSOF, SAMSIDAR HAMZAH and YEANG, H.Y. (2002) Physiological and nutritional aspects in relation to the spontaneous development of tapping panel dryness in clone PB 260. Journal of Rubber Research, 5(3), 135-56.

BOKMA, E., SPIERING, M., CHOW, K.S., MULDER, P.M.F., SUBROTO, T. and BEINTEMA, J.J. (2001). Determination of cDNA and genomic DNA sequences of hevamine, a chitinase from the rubber tree Hevea brasiliensis. Plant Physiology and Biochemistry, 39, 367-76.

YUSOF, F., CHOW, K.S., WARD, M. and WALKER, J.M. (2000) A stimulator protein of rubber biosynthesis from Hevea brasiliensis latex, Journal of Rubber Research, 3(4), 193-210.

LUO, S., XIAO, X., HAMZAH, S. and YEANG, H.Y. (2000) Hev b3 in latex from TPD rubber trees. Chinese Journal of Tropical Crops, 21(2), 7-11.

SAMSIDAR HAMZAH, XIAO, X., LUO, S., CHAN, J.L. and YEANG, H.Y. (2000) Protein marker for tapping panel dryness identified as the small rubber particle protein (Hev b 3). Journal of Rubber Research, 3(1), 42-52.

HAN K.H., SHIN D.H., YANG J., KIM I.J., OH S.K. and CHOW K.S. (2000) Genes expressed in latex of Hevea brasiliensis. Tree Physiology, 20, 503-510.

SHIN, D.H., YANG, J., CHOW, K.S. and HAN, K.H. (1999) A Hevea brasiliensis homolog of DnaJ (HvDnaJ) is expressed abudantly in latex and induced by ethylene (Accession No. AF085275) (PGR99-004). Plant Physiology 119, 363.

CHOW, K.S. (1999) Cloning of a thioredoxin h cDNA from Hevea brasiliensis (Accession No. AFF133127) (PGR99-059). Plant Physiology 120:339.

OH, S.K., KANG, H., SHIN, D.H., YANG, J., CHOW, K.S., YEANG, H.Y., WAGNER, B., BREITENEDER, H. and HAN, K.H. (1999) Isolation, characterisation and functional analysis of a novel cDNA clone encoding a small rubber particle protein from Hevea brasiliensis. Journal of Biological Chemistry 274(24):17132-8.

FARIDAH YUSOF, AUDLEY, B.G., ISMAIL, F. and WALKER, J.M. (1998) A rapid assay for the incorporation of isopentenyl diphosphate in rubber biosynthesis. Journal of Rubber Research, 1(1), 48-66.

FARIDAH YUSOF, WARD, M.A. and WALKER, J.M. (1998) Purification and characterisation of an inhibitor of rubber biosynthesis from C-serum of Hevea brasiliensis latex, Journal of Rubber Research, 1(2), 95-110.

SHAMSUL BAHRI, A.R. and SAMSIDAR HAMZAH (1996) Immunocytochemical localisation of rubber membrane protein in Hevea latex. Journal of Natural Rubber Research, 11(2), 88-95.

YEANG, H.Y. and OTHMAN HASHIM (1996) Destabilisation of lutoids in Hevea brasiliensis latex during early and late flow. Journal of Natural Rubber Research, 11(1), 45-58.

FARIDAH YUSOF, M.A. SITI ARIJA, GHANDIMATHI, H., ZAINAB HAMZAH, SIVAKUMARAN, S. and YEANG, H.Y. (1995) Changes in some physiological latex parameters in relation to the onset of induced tapping panel dryness. Journal of Natural Rubber Research, 10(3), 182-98.

YEANG, H.Y., YIP, E. and SAMSIDAR HAMZAH (1995) Characterisation of Zone 1 and Zone 2 rubber particles in Hevea brasiliensis latex. Journal of Natural Rubber Research, 10(2), 108-23.

Reproductive biology

The continuing improvement in the productivity of the rubber tree, both in terms of latex as well as timber, owes much to its breeding and selection. In Hevea breeding, artificial (hand) pollination plays a pivotal role in generating new and improved cultivars. Nevertheless, problems of poor fruit-set and non-synchronisation of flowering among different cultivars are important constraints in breeding research. Investigations into the reproductive biology of the rubber tree are aimed at alleviating some of these problems.

Fluorescence micrograph of a Hevea pollen tube (t) penetrating an ovule (o).

Publications

HAMZAH S., CHAN, J.L. and YEANG, H.Y. (2002) Pollen tube growth and fruit-set success in Hevea brasiliensis hand-pollination influenced by the choice of clone and female flower. Euphytica, 123, 1-8.

YEANG, H.Y. and CHEVALLIER, M.H. (1999) Range of Hevea brasiliensis pollen dispersal estimated by esterase isozyme markers. Annals of Botany, 84, 681-4.

SAMSIDAR HAMZAH, CHAN, J.L. and YEANG, H.Y. (1999) Hevea brasiliensis seedlings from hand-pollination using cryo-stored pollen validated by isozymes. Journal of Rubber Research, 2(1), 62-8.

SAMSIDAR HAMZAH and CHAN, J.L. (1996) Pollen storage of Hevea. Journal of Natural Rubber Research, 11(2), 115-24.

Latex allergy

Natural rubber latex is used in the manufacture of a wide range of latex goods, the most important being products related to healthcare such as examination gloves. In recent years, there have been many reports that certain proteins found on gloves and other surgical aids made from latex can cause an allergy in sensitised persons. The problem of latex allergy is therefore of direct concern both to the manufacturers and consumers of latex goods.

To resolve the problem of latex allergy, effort has been made to quantitate the very low concentrations of proteins residual in latex goods and to understand the nature and behaviour of such residual proteins. There is ongoing research to isolate, purify and identify the specific allergenic proteins and to clone the genes (cDNA) that encode them. Once the allergens are pinpointed, it would be possible to develop diagnostics for latex allergy, immunotherapy to relieve the effects of latex allergy and immunoassays to control the quality of manufactured latex gloves.

Two-dimensional immunoelectrophoresis of latex glove proteins reacted with rabbit antiserum against the same proteins.

The Latex Allergens

There are 13 recognised latex allergens (proteins that cause allergy) named Hev b 1 to Hev b 13 according to the nomenclature of the International Union of Immunological Societies and the World Health Organisation. Find out more about the latex allergens...

•	Which latex allergens are most commonly responsible for sensitisation to natural rubber latex?
•	Do diagnostic reagents used in skin prick test contain all the main latex allergens?
•	Which is the most potent latex allergen?
	3D model structure of Hev b 4, a glycosylated latex allergen

Publications

A. MALIK, SITI ARIJA M. ARIF, S. AHMAD AND E. SUNDERASAN. (2008) A molecular and in silico characterisation of Hev b 4, a glycosylated latex allergen. Int. J. Biol. Macromolecules. 42(2) 185-190.

Yeang H.Y., S.A.M. Arif, Loke Y.H., Chew N.P. and Mohsin S.M. (2007) Electrophoretic Characterisation of Hevein. J. Rubb. Res. Vol 10(4), 2007, p. 235-244.

M. RAULF-HEIMSOTH, HP RIHS, P. ROZYNEK, R. CREMER, A. GASPAR, G. PIRES, H.Y. YEANG, S.A.M. ARIF, R.G. HAMILTON, I. SANDER, M. LUNDBERG, T. BRÜNING (2007) Quantitative analysis of IgE reactivity profiles in patients allergic or sensitized to natural rubber latex (Hevea brasiliensis). Clin Exp Allergy; 37 (11); 1657-67.

SMITH AM, AMIN HS, BIAGINI RE, HAMILTON RG, ARIF SA, YEANG HY AND BERNSTEIN DI (2007) Percutaneous reactivity to natural rubber latex proteins persists in health-care workers following avoidance of natural rubber latex. Clin Exp Allergy; 37 (9); 1349-56.

S. WAGNER, M. BUBLIN, C. HAFNER, T. KOPP, D. ALLWARDT, U. SEIFERT, S.A. ARIF, O. SCHEINER AND H. BREITENEDER (2007). Generation of Allergen-Enriched Protein Fractions of Hevea brasiliensis Latex for in vitro and in vivo Diagnosis Int Arch Allergy Immunol 2007 , 143 : 246–254

YEANG, H.Y., HAMILTON, R.G., BERNSTEIN, D.I., ARIF, S.A.M., CHOW, K.S., LOKE, Y.H., RAULF HEIMSOTH, M., WAGNER, S., BREITENEDER, H., BIAGINI, R.E. (2006) Allergen concentration in natural rubber latex. Clinical and Experimental Allergy 36, 1078-1086.

ARIF, S.A.M., HAMILTON R.G. AND YEANG, H.Y. (2006) IgE antibody binding to the carbohydrate moiety of Hev b 13, Journal of Rubber Research 9(1) , 40-49.

KOLARICH, D, ALTMANN, F. AND SUNDERASAN, E. (2006) Structural analysis of the glycoprotein allergen Hev b 4 from natural rubber latex by mass spectrometry. Biochimica et Biophysica Acta , 1760(4), 715-20.

SUNDERASAN, E., BAHARI, A., ARIF, S.A.M., ZAINAL, Z., HAMILTON, R.G., and YEANG, H.Y. (2005) Molecular cloning and immunoglobulin E reactivity of a natural rubber latex lecithinase homologue, the major allergenic component of Hev b 4. Clinical and Experimental Allergy , 35, 1490-5.

KURUP, V.P., SUSSMAN, G.L., YEANG, H.Y., ELMS, N., BREITENEDER, H., ARIF, S.A.M., KELLY, K., BANSAL, N.K. and FINK, J.N. (2005) Specific IgE response to purified and recombinant allergens in latex allergy. Clin Mol Allergy , 3, 11.

JOHAR, A., LIM, D., ARIF, S.A.M., HAWARDEN, D., DU TOIT, G., WEINBERG, E.G., MOTALA, C., FIEGGEN, G., YEANG, H.Y. and POTTER, P.C. (2005) Low prevalence of latex sensitivity in South African spina bifida children in Cape Town. Pediatric Allergy and Immunology,16(2), 165-70.

YEANG, H.-Y. and CHOW, K.-S. (2004) DNA cloning of Hev b 2 (Hevea latex ß-1,3-glucanase) and IgE reactivity of the recombinant protein. Journal of Rubber Research 2004 7(3) :180-7.

YEANG, H.-Y., ARIF, S.A.M., RAULF-HEIMSOTH, M., LOKE, Y.-H., SANDER, I., SULONG, S.H., LAU, C.-H., and HAMILTON, R.G. (2004) Hev b 5 and Hev b 13 as allergen markers to estimate the allergenic potency of latex gloves. Journal of Allergy and Clinical Immunology , 114(3) , 593-8.

ARIF, S.A.M., HAMILTON, R.G., YUSOF, F., CHEW, N.-P., LOKE, Y.-H., NIMKAR, S., BEINTEMA, J.J. and YEANG, H.Y. (2004) Isolation and characterization of the Early Nodule Specific Protein homologue (Hev b 13), an allergenic lipolytic esterase from Hevea brasiliensis latex. Journal of Biological Chemistry, 279(23) :23933-41.

YEANG, H.Y. (2004) Natural rubber latex allergens: new developments, Current Opinion in Allergy & Clinical Immunology , 4(2) , 99-104.

BERNSTEIN, D.I., BIAGINI, R.E., KARNANI, R., HAMILTON, R , MURPHY, K., BERNSTEIN, C., ARIF, S. A.., BRENDTS, B. and YEANG, H.Y. (2003) In vitro sensitization to purified Hevea brasiliensis proteins in health-care workers sensitized to natural rubber latex. Journal of Allergy and Clinical Immunology , 111(3) , 610-6.

YEANG, H.Y., LAU, C.H., SITI ARIJA M. ARIF, LOKE, Y.H., CHAN, J.L., SAMSIDAR HAMZAH and HAMILTON, R.G. (2002) Hev b 1, Hev b 2 and Hev b 3 Contents in Natural Rubber Latex and Powdered Latex Gloves. Journal of Rubber Research , 5(3), 167-78.

YEANG, H.Y., ARIF, S.A.M., YUSOF, F. and SUNDERASAN, E. (2002) The allergenic proteins of natural rubber latex. Methods. 27(1) , 32-45.

IKRAM, A., BAHRI, A.R.S., FAUZI, M.S. and NAPI, N. (2001) Effects of added nitrogen and phosphorus on the biodegradation of NR gloves in soil. Journal of Rubber Research , 4 , 102-17.

YEANG, H.Y., CHOW, K.S., YUSOF, F., ARIF, S.A.M., CHEW, N.P. and LOKE, Y.H. (2000) Appraisal of latex glove proteins in the induction of sensitivity to multiple latex allergens. Journal of Investigational Allergology & Clinical Immunology , 10(4) , 215-22.

YEANG, H.Y. (2000) Prevalence of latex allergy may be vastly over-estimated when determined by in vitro assays. Annals of Allergy , Asthma & Immunology , 84 , 628-32.

KURUP,V.P., YEANG, H.Y., SUSSMAN, G.L., BANSAL, N.K, BEEZHOLD, D.H., KELLY, K.J., HOFFMAN, D.R., WILLIAMS, B. and FINK, J.N. (2000) Detection of IgE in the sera of patients using purified latex allergens. Clinical and Experimental Allergy , 30(3) , 359-69.

JOHNSON, B.D., KURUP, V.P., SUSMAN, G.L., ARIF, S.A.M., KELLY, K.J., BEEZHOLD, D.H. and FINK, J.N. (1999) Purified and remcombinant latex proteins stimulate peripheral blood lymphocytes of latex allergic patients. International Archives of Allergy and Immunology , 120 , 270-9.

WAGNER, B., KREBITZ, M., BUCK, D., NIGGEMANN, B., YEANG, H. Y., HAN, K.H., SCHEINER, O., and BREITENEDER, H. (1999). Cloning, expression and characterization of recombinant Hev b 3, a Hevea brasiliensis protein associated with latex allergy in spina bifida patients. Journal of Allergy and Clinical Immunology. 104(5) , 1084-92.

SOWKA, S., HAFNER, C., RADAUER, C., FOCKE, M., BREHLER, R., ASTWOOD, J. D., ARIF, S. A., KANANI, A., SUSSMAN, G. L., SCHEINER, O., BEEZHOLD, D. H., and BREITENEDER, H. (1999). Molecular and immunological characterization of new isoforms of the Hevea brasiliensis latex allergen Hev b 7: Evidence of no cross-reactivity between Hev b 7 isoforms and potato patatin and proteins from avocado and banana. Journal of Allergy and Clinical Immunology , 104 , 1302-10.

AIRENNE, K.J., LAITINEN, O.H., ALENIUS, H., MIKKOLA, J., KALKKINEN, N., ARIF, S.A., YEANG, H.Y., PALOSUO, T. and KULOMAA, M.S. (1999) Avidin is a promising tag for fusion proteins produced in baculovirus-infected insect cells. Protein Expression and Purification , 17(1) ,139-45.

YEANG, H.Y., FARIDAH YUSOF and LATIFAH ABDULLAH (1998) Protein purification for the Lowry assay: Acid precipitation of proteins in the presence of SDS and other biological detergents, Analytical Biochemistry , 265 , 381-384.

YEANG, H.Y., WARD, M.A., ZAMRI, A.S.M., DENNIS, M.S. and LIGHT, D.R. (1998) Sequence similarity of Hev b 3 with two previously reported 27 and 23 kDa latex allergens detected by spina bifida patients. Allergy 53(5) , 513-9.

SOWKA, S. WAGNER, S., KREBITZ, M., SITI ARIJA MAD ARIF, FARIDAH YUSOF, KINACIYAN, T., BREHLER, R., SCHEINER, O. and BREITENEDER, H. (1998) cDNA cloning of the 43-kDa latex allergen Hev b 7 with sequence similarity to patatin and its expression in the yeast Pichia pastoris . European Journal of Biochemistry , 255 , 213-9.

YEANG, H.Y., CHEONG, K.F., SUNDERASAN, E., SAMSIDAR HAMZAH, CHEW, N.P., SHARIFAH HAMID, HAMILTON, R.G. and CARDOSA, M.J. (1996) The 14.6kd rubber elongation factor ( Hev b 1) and 24 kd ( Hev b 3 rubber particle proteins are recognised by IgE from patients with spina bifida and latex allergy. Journal of Allergy and Clinical Immunology , 98(3) , 628-39.

SUNDERASAN, E., SAMSIDAR HAMZAH, SHARIFAH HAMID, WARD, M.A., YEANG, H.Y. and CARDOSA, M.J. (1995) Latex B-serum -1,3-glucanase ( Hev b II) and a component of the microhelix ( Hev b IV) are major latex allergens. Journal of Natural Rubber Research , 10(2) , 82-99.

YEANG, H.Y., SUNDERASAN, E. and HAFSAH MOHD. GHAZALY (1995) Latex allergy studies: Extraction of natural rubber latex proteins with reference to film thickness, latex d.r.c. and protein migration behaviour. Journal of Natural Rubber Research , 10(1) , 46.

YEANG, H.Y., FARIDAH YUSOF and LATIFAH ABDULLAH (1995) Precipitation of Hevea brasiliensis proteins with trichloroacetic acid and phosphotungstic acid in preparation for the Lowry protein assay. Analytical Biochemistry , 226 , 35-43.

Misc Publications

HAMZAH S., CHAN, J.L. and YEANG, H.Y. (2002) Pollen tube growth and fruit-set success in Hevea brasiliensis hand-pollination influenced by the choice of clone and female flower. Euphytica, 123, 1-8.

YEANG, H.Y. and CHEVALLIER, M.H. (1999) Range of Hevea brasiliensis pollen dispersal estimated by esterase isozyme markers. Annals of Botany, 84, 681-4.

SAMSIDAR HAMZAH, CHAN, J.L. and YEANG, H.Y. (1999) Hevea brasiliensis seedlings from hand-pollination using cryo-stored pollen validated by isozymes. Journal of Rubber Research, 2(1), 62-8.

SAMSIDAR HAMZAH and CHAN, J.L. (1996) Pollen storage of Hevea. Journal of Natural Rubber Research, 11(2), 115-24.