Abstract:
leaf spot disease on more than 70 host plant species including Hevea
brasiliensis. The demonstration of high morphological variability among
isolates of this fungus implies the existence of different races or strains.
Variability of 42 isolates of C. cassiicola collected from diverse locations and
hosts in Sri Lanka was assessed using morphological, pathological, biochemical
and molecular genetical studies.
ITS-rDNA region of all the isolates of C. cassiicola exhibited an
identical size. Furthermore restriction endonuclease revealed that all of the
detected DNA fragments’ were identical in size. However, RAPD-PCR
generated from 8 olygonucleotide decamer primers revealed significant
polymorphysm between isolates collected from different host plants.
A significant variation in morphology and virulence existed among
isolates of C. cassiicola. However, there was no correlation between RAPD
groups and the virulence of isolates.
Pectic enzymes of the C. cassiicola isolates collected from different host
plant species showed a similar pattern of secretion and had similar molecular
weights. Although papaya isolate S produced
enzymes and also toxins than the rubber isolates, it was not virulent on rubber.
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a higher amount of pectic
The plant pathogenic fungus Corynespora cassiicola causes a severe
Thus it seems likely that there are other factors involved in the determination
of pathogenicity of isolates.
Scopoletin (7-hydroxy-6-mehoxy coumarin) which inhibited the
conidial germination of C. cassiicola was isolated from uninfected mature
leaves of H. brasiliensis. Scopoletin was not detected in uninfected immature
rubber leaves but on infection with C. cassiicola, the immature leaves also
produced scopoletin. It can be concluded that scopoletin is an antifungul
compound produced by rubber leaves when under stress.
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