Endophytic fungi of Cassia fistula L.
Endophytic fungi from Cassia fistula or golden shower, a well known medicinal plant
in Thailand and Asia, were isolated from trees growing in three geographical
separate sites. These locations were Kanchanaburi, Nakhon Ratchasima and
Bangkok and were selected to allow comparisons between their endophytic
assemblages and to evaluate these data in relation to differences in plant diversity
and density and local environment. Kanchanaburi which was the site closest to a
natural forest situation provided the highest number of isolates with Bangkok, where
the trees were isolated individuals, having the least.
Members of the Xylariaceae proved to be common and frequent isolates especially
species of Xylaria and Daldinia but Nemania and Hypoxylon were also obtained.
Phomopsis was also well represented and clearly was dominant at the
Kanchanaburi site. Species of Fusarium, Colletotrichum, Penicillium, Nigrospora,
Coprinus and Psathyrella were also identified but were occasional isolates.
Differences in endophytic assemblages between samples obtained early in the rainy
season (July, 2001) with those sampled towards the end of the rainy season
(December, 2001) were found to occur in the Nakhon Ratchasima samples with
over twice as many isolates obtained from the December samples. This is likely to
be a reflection on the longer exposure period to the potential inoculum of these
leaves. A total of 956 endophytic isolates were obtained from the three sites with
samples from Kanchanaburi (December 2000) and Bangkok and Nakhon
Ratchasima in July 2001 with a further samples from Nakhon Ratchasima in
December, 2001. Isolations were also made from different anatomical regions of the
leaf, leaf lamina, midrib and veins. There were no appreciable differences in either
the number of isolates obtained or an association between leaf area and specific
Identification of many xylariaceous endophytic isolates is well known to be
problematic since Xylaria species rarely produce their anamorphic form in culture
and virtually no members of the Xylariaceae develop their teleomorph in culture.
Therefore molecular techniques were used to compare DNA sequences of the ITS
region from a selection of endophyes with sequences obtained from teleomorphic
material, or cultures derived from teleomorphs of identified and authenticated
Xylariaceae. Comparisons were also made with data held in GenBank. This enabled
the identity of a number of taxa to be made although more sequences from Xylaria
species are required for future investigations. A number of non-xylariaceous taxa
were also named as a result of DNA sequence comparisons.
Secondary metabolites from the xylariaceae were also investigated and their
metabolite profiles used to support identifications. The metabolite profiles proved to
be a useful tool to confirm doubtful endophytic isolates when their DNA sequences
could not place them with certainty in a right group. Together with extracts from
other endophytic species, their inhibitory effects on bacteria and fungi were tested.
Cassia endophytes were found to show low antimicrobial activity. However, they
may later be shown to have other activities when when tested e. g. anti-malarial,
anti-cancer and anti-HIV.