A case study of investigating fungi that affect traditional Japanese shake roof with/without copper plates
T Wada, Y Fujiwara, Y Fujii, R Kigawa
A Japanese traditional shake roof is made from split logs. To keep the roof long, copper (Cu) plates are often inserted between the shakes. It has been thought that Cu elements from copper plates would flow out when a shake roof is exposed to rain and inhibit growth of wood rotting fungi. Actually there are some examples where the Cu plates seem to be effective in preventing fungal damage, but on the other hands, there are also cases that significant rot is observed even with insertion of Cu plates. It is important to look at what is going on in such wooden roofs, by describing levels of damage of rot and investigating fungal species, which are involved in the damage. In this study, we investigated a case of shake roof where Cu plate usage seemed to have inhibited wood rot. Wooden parts away from copper plates were decayed with deep cracks, and wooden parts under a copper plate have been preserved well and maintained its original form. Wooden samples, which did not have significant decay visually, were taken from the areas just under copper plates. Also wooden samples, which had severe decay, were taken from areas without copper plates. Filamentous fungi in both types of samples were identified using a cultivation method on malt extract agar (MA) medium and a non-cultural method, the next generation sequencing method. Fungal strains were isolated on MA plates from ethanol-sterilized wooden pieces and non-sterilized pieces respectively, to see fungal species rich on the surface and inside the wooden pieces. Surface sterilization resulted in a big difference from the results obtained with non-sterilized samples. But for now it is unclear whether there are difference in fungal species between the samples taken from the areas adjacent to Cu plates and samples taken from the areas without Cu plates. By using next generation sequencing technology, 12826 (Sample 1, away from copper plates) and 7086 sequences (Sample 2, just under a copper plate) were yielded. ITS DNA sequences from Sample 1 (samples taken from areas without Cu plates) were divided into 3 groups. The main group (11619 sequences) was highly-homologous to species classified as wood rot fungi. The other groups were classified as ascomycetes. On the other hand, ITS DNA sequences from Sample 2 (samples taken from the areas adjacent to Cu plates) were divided into many groups but all the sequences were classified as ascomycetes. Such difference may reflect the states of wood rot, between the Cu plus and Cu minus samples examined in this study.
Keywords: Japanese traditional shake roof, copper (Cu) plates, fugal flora, wood rotting fungi, cultivation method, next generation sequencing method