Cloning and characterization of a laccase gene from <em>Ganoderma</em> spp. causing basal stem rot disease in coconut

Abstract

Basal stem rot disease in coconut is caused by the white-rot fungus Ganoderma lucidum, which is soilborne in nature. Its degree of virulence is governed by the activity of the laccase enzyme. Of twenty-five isolates belonging to the genus Ganoderma obtained from different host species, the isolate from Silent Valley (SV) showed the greatest laccase activity in vitro, followed by the isolate from Veppankulam (CRS-1). These two isolates also reacted positively in the laccase assay in vitro. The laccase-positive SV and CRS-1 isolates were further amplified by polymerase chain reaction (PCR) using degenerate primers for the partial sequence, which showed the fragment size of 200 bp. The highly virulent SV isolate was cloned in a plasmid vector and sequenced. It was confirmed as a partial-length laccase gene and submitted to the GenBank database. The nucleotide sequence of the DNA of this isolate showed high homology with those of the laccase genes of other basidiomycetes.