Browsing by Author "Nishantha, N.A.D."

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    Variability of Corynespora cassiicola Isolates from Non-Traditional Rubber Growing Areas
    (Uva Wellassa University of Sri Lanka, 2013) Udayasiri, G.R.P.N.; Chandrasena, G.; Fernando, T.H.P.S.; Nishantha, N.A.D.
    Corynespora leaf fall disease (CLFD) caused by Corynespora cassiicola (Berk and Curt) is the most distructive foliar disease reported in Sri Lanka and it has become a serious threat to the world natural rubber industry (Fernando et al., 2012). CLFD was first detected in Sri Lanka during the year 1985 and the first epidemic was experienced in 1985-1986, devastating the clone RRIC 103, one of the most prestigious genetic materials bred by Sri Lankan scientists. Very recently, a leaf spot disease with uncommon symptoms was reported from non- traditional rubber growing areas. The disease samples were collected from the field plants of RRIC 121 and the isolation of the samples consistently resulted Corynespora cassiicola isolates. The objective of this investigation was to report the newly recorded disease symptoms, isolate the pathogen and also to study the variability in cultural and reproductive characteristics. Methodology Diseased leaf samples were collected from the several traditional and non- traditional rubber growing areas and the different symptoms were recorded. Five isolates were collected, purified and single conidia cultures were raised on to potato dextrose agar (PDA). Mycelial plug (5.0 mm) from the advancing margin of a seven-day old culture of the test isolates and were placed at the centre of Petri plates containing PDA. The plates were incubated at RT under normal light and dark regimes. Colony colour, texture and the growth were recorded after 8 days of incubation period. The growth was also recorded. The cultural characteristics in different culture media were also observed. Ten-day old cultures of the isolates grown on PDA were used to prepare conidia suspensions. Reproductive characteristics were evaluated by using slide cultures, conidia shapes and their sizes. The conidial concentration of the filtrates was measured using a haemocytometer. Pathogenicity of the isolates was tested a concentration of 2×10 conidia/ ml) were used for artificial inoculations. Apple green leaves of the clone, RRIC121 clone were used for pathogenicity tests. Toxin production was evaluated by using leaf wilt bio assay and leaf puncture bio assay.