Journal of the Rubber Research Institute of Sri Lanka
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Item Shoot tip culture as a method of micropropagation of Hevea(Rubber Research Institute. Agalawatta, 1988) Gunatilleke, I.D.; Samaranayake, C.Shoot tips of Hevea from aseptically grown seeedlings were established in culture on Murashige and Skoog (MS) liquid medium with half strenth salts, supplimented with BAP +IBA or MS solid medium, with full strenth salts with and without BAP + IBA. BAP was found to be better for axillary bud proliferation and growth than the other cytokinines. Proliferation of buds improved with successive subcultures. A multiplication rate of 30 + 2 shoots per explant was obtained with threee subcultures in 165 daysItem Effect of potassium and magnesium on growth of young Hevea brasiliensis(Rubber Research Institute. Agalawatta, 1988) Weerasuriya, S.M.; Yogaratnam, N.The effect of potassium and magnisium fertilisers on growth of young Hevea brasiliensis were studied using clones PB 86, RRIC 100, RRIC 103, and RRIC 121 with the objective of determining the requirement of these elements during the early phase of establishment of these clones. Three commercial fertilisers were evaluated as of magnesium. Potassium requirement of clone PB 86 during the first year was found to be approsimately 33g K/plant/year. It was found that clones. RRIC 100 and RRIC 121 needed higher amount of K than PB 86 for normal growth. Potassium application caused an overall reduction in growth of clone RRIC 103 where the soil K level was 0.07 me./100g suggesting that this level is adequate for this clone during its first year of growth. Total dry weight was significantly increased when Mg application was increased from 11 to 22g/plant/year in clone RRIC 103 but such effects were not seen in clones PB 86, RRIC 100 and RRIC 121Item Secondary characters and their association with latex yield in Hevea brasiliensis(Mull Arg.)(Rubber Research Institute. Agalawatta, 1988) Olapade, E.O.Ten Hevea clones developed at the Rubber Research Institute Of Nigeria (RRIN) and a control clone RRIM 600 were evaluated for their latex yield after six months of tapping. The mean dry latex yield recorded for each clone was correlated with their Juvenile secondary characters i. e Height, Girth and Plant Vigour at 18 months. Significant variability was exhibited by the clones in terms of yield with clone C 83 having the highest mean latex yield of 42.15 g/t/t/ while clone C 202 had the least mean yield of 22.73 g/t/t. The secondary characters i. e Hewight, Girth and Vigour were significantly positively correlated to themselves but all negatively correlasted to latex yield. However a spurious correlation was established between latex yield and the secondary characters. The implication of the results are discussedItem An analysis of growth patterns of Hevea clones(Rubber Research Institute. Agalawatta, 1988) Margret, H.A.W.; Abeyasekera, S.; Jayasekera, N.E.M.Four girth measurements collected over four years, before tapping from ten Hevea clones grown in two sites have been analysed to study the growth pattern. Year to year variation in both sites was mainly due t linear component of growth. Growth of individual clones too was mainly due to linear effect. But some clones in one site showed significant quadratic and or cubic component. This was due to non linear growth of plants in some plots. Ten clones have been groued (a) according to the when averaged over four years so that clones within a group have the same average girth and (b) on the gradient of the regression fitted to the girth measurement increasing over the four years. RRIC 52 had the fastest growth in both sites. RRIC 103 had the same growth rates in both sites suggesting that it has a greater stability to local environmental changes.Item Virgin bark tapping of some RRIC 100 series clones(Rubber Research Institute. Agalawatta, 1987) Samaranayake, C.; Waidyanatha, U.P. De S.; Pathiratne, L.S.S.; De Soysa, A.G.A.All RRIC 100 series clones reached tappability much earlier than the two control clones viz. RRIM 600 and PB 86. Significantly higher yield per tree per tapping was obtained in the first year on a 1/2 S d/3 system compared to 1/2S d/2 tappings in many of the clones tested. However, during the second year there was no significant differences in yields obtained on both frequencies indicating that the tree was able to replenish the latex removed in a tapping, much faster than in the first year of tapping. The data presented indicate the possibility of tapping all recommended clones on 1/2S d/32 system of tapping from the second year, without any adverse effects.Item Clonal differences in growth parameters of young Hevea buddings and their relation to field performance(Rubber Research Institute. Agalawatta, 1986) Nugawela, A.; Aluthhewage, R.K.Hevea trees when tapped exhibited a depression of girth increment and canopy growth. Hence a high growth rate is required to maintain the growth whilst giving a high yield. Growth parameters of 5 Hevea clonal buddings were determined after different growth intervals viz., 3, 6 , 9, and 12 months to study the correlation they show with the field performance of the same clones. Clonal differences were significant, but did not necessarily correlate with the field performance. Growth rates gradually increased with age during the peeriod of investigatiion. Thepossibility of using growth parameters together with gas exchange capacities determinedin earlier studies in predicting later field performance are discussed.Item Accumulation of free proline in bark and latex of Hevea brasiliensis affected by brown bast(Rubber Research Institute. Agalawatta, 1986) Wickramasinghe, S.I.; Yapa, P.A.J.; De Soysa, T.V.W.Free proline accumulation in clone RRIC 101 of Hevea brasiliensis was investigated. The bark and the latex samples collected from both healthy and brown bast effected trees were analysed for free prline content. The average bark proline concentration/unit present in the brown bast trees was found to be considerable higher (P = 0.10) than that of healthy trees. The accumulation of free proline in latex was found to be significant in brown bast trees.Item Reaction of oriental Hevea clones to isolates of Microcyclus ulei and the response of isolates to fungicides(Rubber Research Institute. Agalawatta, 1986) Fernando, E.B.; Hashim, I.Hevea clones from Sri Lanka, Malasia and India were assessed in vitro for their resistance to four isolates of microcyclus ulei. Clones SL 26, R-14, 5B/17/4, and 1/2/56/77 were infected by all isolates of M. ulei tested. However, they were found to have some resistance to M. ulei. Propiconazole was more effective than Triforine and Triadimefon in inhibiting germination of conidia of M.ulei. These fungicides were also effective in inhibiting lesion formation. Triadimefon (Bayleton 50 w.p.) had a better curative effect than propiconazole (Tilt 25 EC) and Triforine (Saprol). The effect of Triadimefon on germination of conidia varied between isolate while the effect varied little between isolates for propiconazole and triforine. The effect of the fungicides on the number of lessios on leaf discs did not show major differences between iaolates.Item Effect of different levels of supplemental nitrogen on CO2 assimilation rates and productivity of Pueraria phaseoloides (Roxb) Benth and Desmodium ovalipolium (prain) wall. ex ridely grown in agalawatta series soil(Rubber Research Institute. Agalawatte, 1985) Nugawela, A.; Jayasinghe, C.K.; Aluthhewage, R.; Wettasinghe, S.Plant dry matter production is linked to CO2 assimilation rates, respiratory losses and total leaf area. Experiments were undertaken to determine the effect of different levels of supplimental nitrogen given to legume cover crops, on their CO2 assimilation rates and productivity. They were found to be highest for Pueraria phaseoloides and Desmodium ovaliforlium when given around 140 and 35 ppm of supplimental nitrogen. Reciprocal of specific leaf area and laef nitrogen content were also determined and they showed a positive linear relationship with supplemental nitrogen levels. How nitrogen could a influence the CO2 assimilation rates of cover crops studies are discussed.Item Gas exchange parameters for early selection of Hevea brasiliensis Muell. Arg(Rubber Research Institute. Agalawatte, 1985) Nugawela, A.; Aluthhewage, R.K.Selecting high yielding progeny from Hevea breeding programmes is a money and time consuming approach and limits the progress of breeding, Girth, bark thickness, numberof lates vessel rings, latex vessel density and first few years yield of 7-8 year old Hevea budding are reported to be correlated to the yield potential. These parameters are used by some breeeders for a primary selection using smalle scale clone trials. Latex is biosythesised from sucrose in latex vessels and the potential of sucrose supply to latex vessels depends on CO2 assimilatory capacity of the canopy and the partitioning of assimilates. Attempts were made to estimate the mean CO2 assimilatory capacity of a healthy and a matur eleaf whole in year old Hevea clonal buddings. Preliminary studies show the mean CO2 assimilatory capacity of a whole and its ratio with water use efficiency value to be correlated qith yield potential. These observation suggest that effective selection of clones for further testing in large scale clone trials could be done on this basis, when buddings are around a year old.