Wood-rotting basidiomycetes are a minor component of fungal communities associated with Acacia hybrid trees grown for sawlogs in South Vietnam

Acacia hybrid (Acacia mangium x Acacia auriculiformis) clones are widely planted in Vietnam with a total of approximately 400,000ha to meet the demand for pulpwood, sawn timber and wood chip exports. Silvicultural techniques such as pruning and thinning have been applied to improve productivity and sawlog quality of Acacia hybrid plantations. However, those techniques may also create opportunities for wood decay fungi to enter the Acacia hybrid stems through wounds and cause stem defects that reduce sawlog quality and the value of the plantation. The presence of fungal decay agents in Acacia hybrid trees was examined in two Vietnamese plantations. In July 2011, just prior to a second thinning, discoloured wood samples were taken from a three-year-old Acacia hybrid plantation at Phan Truong Hai for the isolation of fungi. In July 2012, approximately 18months after pruning and thinning treatments, discoloured wood samples were taken from a three-year-old Acacia hybrid plantation at Nghia Trung for the isolation of fungi. DNA sequencing of the rDNA ITS identified the isolates. In May 2015, approximately 4years after thinning and fertilizer treatments, discoloured and decayed wood samples were taken from the above (7-year-old) Acacia hybrid plantation at Phan Truong Hai for fungal identification. DNA was extracted directly from discoloured and decayed wood samples and fungal rDNA ITS amplicons sequenced on a Roche 454 sequencer. The results showed that silvicultural treatments did not affect the fungal communities associated with discoloured and decayed wood of Acacia hybrid plantation at Phan Truong Hai. A total of 135 fungal species or OTUs (operational taxonomic units) were identified, including 82 members of Ascomycota and 52 Basidiomycota.