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Item Toxic metabolite from clove isolate of Cylindrocladium quinqueseptatum(Rubber Research Institute:Agalawatta, 1999) Jayasinghe, C.K.; Wijesundera, R.L.C.Cylindrocladium Quinqueseptatum Boedijn Reitma causes seedling blight and extensive defoliation on a wide variety of plants and is widely distributed in the humid tropics.It is a serious pathogen of Eugenia caryophyllata in Sri lankaand has been identified as a potential lpathogen on Hevea brasileensis in the eastern Hemispher .All cloveisolates;IMI 342173 (rt),359378(Aw),359379(Rw)and 359380(Kp) of c.quinqueseptatum tested were found to be capable of secreting toxic substances to the growing medium.Toxic culture filtrates proved to be thermostagbl4e(up to 100C)and host specific.The type and the size of the lesions lproduced by the crude toxin of different isolates varied markedly.Isolate,Rt produced the largest lesions (Highest score) indicationg its aggressive nature in toxin production while Aw and Rw isolates showed a mild reaction.When the reaction of Hevea clones towards the crude toxin was considered three main clusters ofclones were distinguished through cluster analysis indicationg the marked variation of Hevea clones grown in the Eastern Hemisphere in their sensitivity to the crude toxin.The possibility of making use of this toxin as a tool in screening Hevea populations for cylindrocladium leaf spot disease has also been discussed.Item Cell wall degrading enzyme secretion by Cylindrocladium quinqueseptatum(Rubber Research Institute:Agalawatta, 1999) Jayasinghe, C.K.; Wijesundera, R.L.C.Cylindrocladium quinqueseptatum causes leaf fall of clove in Sri Lanka and is responsible for the leaf spots of rubber in Malaysia.only one isolate (KP)from four pathogenic isolates examined secreted polygalacturanase(PG) when grown in liquid media.None ofthe isolates secreted pectin lyase(PL).The extracts of clove and rubber leaf tissues,inoculated with the KP isolate did not show any PG and PL activity .The leaf tissue did not have the ability to ingibit c.quinqueseptatum PG produced in culture.All isolates of C.quinquesepltatum secreted cellulases viz.cellobiase and b-glucosidase in culture.cellobiase was detected in the inoculated rubber leaves,The levels of B-glucosidase,an ingerent enzyme of Hevea leaves,also increased rapidly following infection.The results indicate that pectic enxymes play a minimal or no role in disease developmet of C.quinqueseptatum infecton in cloves and Hevea.Thus cellulolyic enzyme probably play a nutritive role.Item The rubber seed production in Sri Lanka. results of an islandwide survey(Rubber Research Institute:Agalawatta, 1999) Seneviratna, P.; Witharana, L.P.P.; De Alwis, M.N.Seed Production of rubber plantations in certain areas of Sri Lanka has gone down to very low levels affecting the quality of the planting material I.e.budded stump.An island wide survey was therefore conducted to gain soem knowledge on the quality and the quantity of the seeds produced on different clones in different climatic regions of Sri Lanka.the results confirmed that the regional effects most probably owing to climatic and weather factors are the main causes while the clonal effect was minimum.It was evident that the seed production in dry region is far more than the country's requirement for the production of budded stumps for annual repllanting programme.Item Quality improvement of radiation vulcanized natural rubber latex by addition of polyvinyl alcohol and centrifugation(Rubber Research Institute:Agalawatta, 1999) Ratnayake, U.; Makuuchi, K.; Yoshii, F.Effect of polyvinyl alcohol(PVA)on extractable soluble protein content,and on mechanical and physical properties of radiation vulcanized natural rubber latex(RVNRL)was studied with the view of improving properties of RVNR latex.Concentrated natural rubber latex was irradiated at the rate of 10 kgy/h for 2hrs in the presence of 5 phr of n-BA and 0.5 phr of KOH.PVA solution was added to the RVNR latex at three different stages and different time periods were used for leaching to find out the most suitable process to produce soluble protein less RVNR latex.present results indicate that combined treatments of PLVA addition and centrifugation foollowed by leaching were more effective compared to single treatmemt to reduce soluble protein content in RVNR latex films.It could be further observed that,the tear strength was increased whereas tensile strength and tackiness were decreased with PVA concentration.However when the PVA incorporated RVNRL was centrifuged,tensile and tear strenght were not changed up to 2 phr of PVA.Fourier Transrorm infrared slpectrophotometer (FTIR)measurements showed that whem PVA added RVNRL was centrifuged,most of the PVA could be removed with the serum phase,According to the Horixontal Attenuated Total reflectance(HATR)measurements ,PVA concentration on the upper and lower surfaces of the latex films (I.E.the exposed and unexposed surfaces of the films whem drying )was not equal.Item Blends of acrylonitrile butadiene rubber/superior processing/natural rubber and poly(vinyl chloride) Part I. a study of some of the technological properties of NBR/SP rubber/NR/PVC blends(Rubber Research Institute:Agalawatta, 1999) De Silva, K.G.K.; Karunanayake, L.; Muttukkrishnan, K.The advantage s of using superior processing(SP)rubber in place of natural rubber (NR) in blends with NBR and NBR/PVC is discussed here in derail.various technological properties such as tensile,resilience,hardness,compression set,specific gravity,cross-lind density and resistance to oil were measured and compared. It is advantageous to use SP rubber in place of NR in the above blends probably due to higher cross-link density in the SP rubber component when compared to NR. It may be possible to use the ternary blends of SP/PVC? NBR in manufacture of injection moldable and recyclable products due to their thermoplastic natureItem Preliminary studies on the use of neutron probe in some rubber growing soils(Rubber Research Institute:Agalawatta, 1992) Samarappuli, L.; Yogaratnam, N.; Karunadasa, P.; Mitrasena, U.Studies carried out on the use of Neutron Probe in soil/water relations indicate that this can be used as an effective technique in immature Hevea plantations. It had been possible to establish a fairly reliable calibration curve for the subsurface soil 10 - 160 cm the calibration curve obtained is moisture content, Qv = 0.52 CR - 0.39, where CR stands for Count Ratio. It appears that during dry period, distances varying from 0 - 1.2m from the trunk of the tree are suitable for assessing the water content of the soil profile. The available soil water storage capacity of 104.2 mm with the upper lower limits of 235.5 131.3mm, respectively, is likely to be the amount of water that is available to the plants, both rubber covers over a period of 12 months.Item Improving phase morphology and properties of NR/NBR blends with compatibilizers(Rubber Research Institute:Agalawatta, 1998) De Silva, K.G.K.; Lewan, M.Two compatibilizing agent have been identified for NR/NBR blend to improve the phase morphology and interfaial adhesion, thereby improving the physical and technological properties. Light and optical microscopy and Nuclear Magnetic Resonance have been used to study the phase contrast and crosslink distribution of the elastomer blends respectively, to suport the observations mode on the improvements in the physical properties of these blends.Item Shade effects on photosynthesis of cinnamon (Cinnamomum verum J. Pres)(Rubber Research Institute:Agalawatta, 1998) Pathirana, L.S.S.; Nugawela, A.; Samarasekera, R.K.Item Cultural characteristics and reproductive morphology of Geotrichum sp.. a guide to distinguish Geotrichum from Rigidoporus microporus(Rubber Research Institute:Agalawatta, 1998) Jayasinghe, C.K.; Wettasinghe, J.L.P.C.Culture characteristics of Geotrichum sp. isolate IMI 354411, a fungus responsible for the saprophytic colonization on Hevea roots are described. It was also shown that this fungus could be easily distinguished from Regidoporus lignosus, a devastating pathogens of Hevea roots, by the zonate and cloudy appearence of its colonies on malt agar with a cream undersurface and the disarticulating hyphae which later break upto arthric conidia.Item Some aspects of biochemical changes due to maturation of acid and papain treated Hevea latex(Rubber Research Institute:Agalawatta, 1998) Dissanayake, W.; Yapa, P.A.J.Biochemical changes that occur due to maturation of acid and papain treated Hevea latex were investigated. An increase in bacterial population in latex of both acid and papain treated, was significantly higher than that in acid treated latex. Higher microbial activity correlated with decreases in carbohydrate and amino acid levels in serum. Maturation of papain treated latex, enhances protein digestion and reduction in ash content without any adverse effect on major raw rubber properties.