Journal of the Rubber Research Institute of Sri Lanka
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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 A study of isolates of Rigidiporus lignosus. the causative agent of the white root disease of rubber(Rubber Research Institute. Agalawatta, 1991) Wijesundera, R.L.C.; Prelis, S.P.; Liyanage, N.I.S.Rigidporus lignosus (Klotz.) Imazaki cause the whiteroot disease of rubber (Hevea brasiliensis). Five isolates of the fungus, T1, 01, S1, F1 H2, obtained from different rubber growing districts of Sri Lanka, were examined for their growth patterns in different solid media. The secretion of cell wall degrading enzymes was also studied in the isolates T1, S1 H2 when grown in different media with different sources of carbon. The isolate T1, which is known to be the most virulent, grew fast densely on nutrient rich solid media such as potato dextrose agar (PDA) malt extract agar (MEA), but its growth was poor on Czapek Dox agar, Knop-Glucose agar the medium for wood rotting fungi. The other four isolates also grew best on PDA MEA, but the growth was less than that in T1. The growth of S1, O1, F1 H2 on the other media however, was more than that of isolate T1. All isolates except T1 formed branched, strand-like aggregations when growing on solid media. Statistical analysis of the growth studies indicated that a significant difference existed among the isolates also between the isolates the media. The isolate T1 secreted polygalacturonase, pectin lyase, B-glucosidase cellobiase. In T1, the secretion of all the enzymes occurred earlier the amount of enzyme secreted was also higher than in the other two isolates. No polygalacturonase, however, was detected when T1 was grown in the medium with the water insoluble component of rubber roots as the main source of carbon. The pH for optimum activity of polygalacturonase was 6.5 while that for pectin lyase was 10.0.Item Use of Rubber Factory Effluent as a Fertilizer for Young Hevea Plants(Rubber Research Institute. Agalawatta, 1993) Soyza, S.; Yogaratnam, N.; Yapa, P.A.J.The effect of application of crepe factory effluents on the growth of young Hevea plants was investigated.Five treatments namely normal fertilizer, half normal fertilizer diluted serum 1:1, diluted serum 1:1, diluted serum 1:2 undiluted serum were tried out.Significant growth improvement in both height girth were observed with all 4 serum treatments, after the 20th week.Item Effects of combined nitrogen on nodule function of leguminous crops with special reference to tropical soils(Rubber Research Institute. Agalawatta, 1991) Jayasinghe, C.K.The effect of combined nitrogen on nitrogen fixation has been discussed by several investigators from their findings it could be concluded that inorganic nitrogen may have either stimulatory, neutral or negative effect on nitrogen fixation depending on the type of legume soil condition. It was reported in some instances that low levels of combined nitrogen especially when applied as a "Starter" fertilizer at germination, stimulates plant growth enhances nodule mass nitrogen fixation. On the other hand when most of the legumes are grown in soil high in available nitrogen, the nitrogen fixation rate is severely affected. This phenomenon may become more critical when legumes are grown as cover crops where non legume counterpart is fertilized with nitrogenous fertilizer. The degree of inhibition appears to vary with several factors viz. concentration of combined nitrogen, host species, cultivar, strain of of root nodule bacteria, rate of inoculation, light intensity temperature. However, the most critical factor is the concentration of combined nitrogen it has been shown that very low concentrations such as 240 ppm N reduced the nitrogen fixation of bradyrhizobia - legume symbioses whereas 80-100 Kg of N ha-1 inhibited the nodulation nitrogen fixation of Vigna spp. totally. It was further pointed out that extra caution should be taken when recommending nitrogenous fertilizer to mixed cropping systems in tropical soils as nodulation nitrogen fixation of legume counter parts such as Pueraria, Desmodium Mimosa were reduced to neglegible levels when 140 ppm N was added to Sri Lankan rubber soils.Item Test methods for rubber bleaching agents(Rubber Research Institute. Agalawatta, 1991) Kumara, P.H.S.; Weeraman, S.Item Country plans and programmes for rubber development and FAO assistance(Rubber Research Institute. Agalawatta, 1977) Gunawardena, K.J.