Endophytic fungi of Tectona grandis L. (Teak).
Taxonomic diversity, biology and ecological aspects of fungal endophytes of
Tectona grandis (teak) from Chiang Mai Province, Thailand were investigated. It was
found that the endophyte assemblages of mature leaves sampled from natural forest and
plantation teak were not significantly different. Members of the Xylariaceae, especially
Daldinia eschscholzii, Nemania subannulata, Hypoxylon haematostroma and Xylaria
cubensis were frequent isolates. Widely reported endophytic fungi such as Phomopsis,
Colletotrichum, Cladosporium and Fusarium were also isolated. There is little evidence to
support host specificity for the majority of the isolates.
Differences in endophyte assemblages between young and mature leaves were
shown to occur with a much lower infection percentage in the young leaves. Species of
Phomopsis and Colletotrichum were dominant in the young leaves but members of the
Xylariaceae dominated in mature leaves. This pattern was the same for both natural forest
and plantation samples.
However comparison of taxa isolated from leaf lamina, midrib and veins gave
conflicting results. Samples from mature leaves from natural forest trees exhibited little
variation with greater variation in taxa recovered being found to occur between sampling
years than between position of isolation from the leaf. In plantation leaves, although the
results were similar to those from natural forest tree leaves for two of the years sampled, in
1997 the overall recovery rate was highest for the lamina, followed by veins and then the
midrib. There was no evidence obtained to link individual taxa with specific regions of the
leaf. It is now possible to devise a sampling strategy to obtain suitable diversity of
endophytic isolates from teak leaves for industrial screening of these fungi.
Techniques were developed to overcome current problems of identification of
xylariaceous endophytes in the absence of their teleomorph. Inoculation of suitable woody
substrata combined with selective incubation was used to induce teleomorph formation in
many of the isolates and this together with chemical profiling enabled identification to
species of many of these isolates. Rates of development of specific species were obtained
and differences in environmental conditions necessary for development of teleomorphs to
maturity were noted for members of different genera. Thus species of Daldinia and
Hypoxylon required drier conditions than species of Xylaria and Nemania which only
developed under wet shaded conditions.
Xylariaceae from the natural forest, plantation, and forest surrounding the
plantation were surveyed and a number of the Xylariaceae recovered as endophytes were
found to be new to science, new records for Thailand or were recorded as endophytes for
the first time.