Journal of the Rubber Research Institute of Sri Lanka
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Item In vitro evaluation of fungicides against rubber isolate of Thanatephorus cucumeris and management of Thanatephorus foot rot of Hevea seedlings(Rubber Research Institute. Agalawatta, 1997) Jayasinghe, C.K.; Fernando, E.B.; Fernando, B.I.Thanatephorus cucumeris, the causal agent of target leaf spot disease of Hevea also attacks the hypocotyls of germinated seeds and cause damping off and foot rot of seedling in Hevea nurseries in Sri Lanka. Sixteen fungicides were screened for their abilities to reduce the saprophytic growth of T.cucumeris on agar and in soil while five fungicides were tested to control foot rot of Hevea seedlings in pots. Five fungicides (benomy 1,Metalaxyl 8% + mancozeb 64%, tebuconazole, thiram and tridemorph) were found to be effective in inhibiting fungal growth 100% (EC 100 %) on agar at a very low concentration of 50 ug/ml. Three fungicides,viz.captan,mancozed,oxadixyl 10% + propineb 56%, pencycuron,propineb and triadimenol) showed EC 100 between 200-800 ug/ml.However,only four fungicides (benomyl,pencycuron,propineb and tebuconazole)reached the EC 100 within the tested range when assessed in the presence of soil indicating that these are the potential fungicides in management of rubber isolate of T.cucumeris. In pot culture trials two fungicides,pencycuron and benomy1 were found to be effective in controlling the disease.However,the disease was completely checked by traditional burning of soil.Item Susceptibility of different leaf stages of Hevea to Corynespora cassiicola(Rubber Research Institute. Agalawatta, 2010) Fernando, T.H.P.S.; Jayasinghe, C.K.; Wijesundera, R.L.C.; Siriwardena, D.Item A comparative study of Colletotrichum species causing anthracnose in Hevea(Rubber Research Institute. Agalawatta, 2009) Jayasinghe, C.K.; Fernando, T.H.P.S.; Jayawardana, N.Item Mycoflora associated with Hevea phylloplane(Rubber Research Institute. Agalawatta, 2000) Jayasinghe, C.K.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 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 Production of cell wall degrading enzymes by Corynespora cassiicola in culture and infected rubber tissue(Rubber Research Institute. Agalawatta, 1998) Jayasinghe, C.K.; Fernando, T.H.P.S.; Priyanka, U.M.S.All isolates of Corynespora cassiicola used in the investigation secreted pectin lyase when grown in liquid medium with pctin as the main source of carbon. However, none of the isolates secreted polygalacturonase in the same medium. The extracts of rubber tissue inoculated and infected with C. cassiicola also showed only pectin lyase activity. When grown in liquid medium with carboxymethyl cellulose as the main source of carbon all isolates secreted cellulases viz. cellobiase and ß - glucosidase. The result of this study suggest that principal pectic enzyme involved in pathogenesis of the rubber isolates of C. cassiicola is pectin lyase and in the later stages cellulolytic enzymes possibly play a major role