Abstract:
Wood decay is a biological process by which cellulose and lignin are converted into
carbon dioxide and water. This process is important for forest sustainability since it
uses cellulose and lignin, the two most abundant organic compounds on earth to
recycle nutrients. Nearly 83% of the total forest coverage in Sri Lanka is comprised
with dry mixed forests and these forests are rich in hard wood bearing plant species
such as Diospyros ebenum, Manilkara hexandra and Drypetes sepiaria. Therefore,
fungi associated with decaying these hard wood species should also be efficient
lignin and cellulose degraders with possible biotechnological importance. The
objective of the current study was to identify such decaying wood-associated fungi
found in a dry zone forest using DNA barcoding approach and to maintain these
cultures for future research. Decaying hard wood pieces were collected from the
forest floor of Dimbulagala forest reserve and brought to the laboratory. Wood pieces
were surface sterilized, cut into small pieces, plated on selective PDA media. Pure
cultures of fungi were obtained and morphological characterization was done. For
molecular characterization, fungal mycelia grown in PDB were subjected to total
genomic DNA isolation. Fungal rDNA-ITS region was amplified and sequenced
from both directions. Sequences were manually edited and BLASTN searches
reveled that Trichoderma species and Lasiodiplodia species were among the
frequently found species. Species delineation of certain fungal isolates were
challenging and therefore, molecular phylogeny based identification was applied.
Maximum Likelihood method based on the Kimura 2-parameter model was used and
interestingly Pleurostomophora richardsiae (isolate name DDW 05), a possible plant
pathogenic fungus, was found to be associated with a decaying hard wood sample.
P. richardsiae has been reported to cause grapevine dieback and cankers in Italy and
Spain. This finding is interesting since forest dieback has long been an unidentified
problem in Sri Lanka and it could be possible that P. richardsiae is among the
organisms causing forest dieback and cankers in Sri Lanka. Previous reports also
show that this fungus has been isolated from wood, ground wood pulp, sewage and
soil in North America, Europe, Africa and several countries in Asia. Therefore,
further research is needed to confirm the pathogenicity of the isolate.
