Variability of Corynespora cassiicola Isolates from Non-Traditional Rubber Growing Areas
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
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.
Description
Keywords
Agriculture, Export Agriculture, Rubber Production, Rubber Technology, Non-Traditional Rubber