Effect of wood moisture on ability of Sphaeropsis sapinea to colonise Pinus radiata
B Kreber, D R Eden, R N Wakeling, C M Chittenden, J G Van der Waals, B Carpenter
The factors influencing colonisation of unseasoned radiata pine logs by sapstaining fungi which can result in detrimental wood discolouration, are being explored. The objective of the current study was to determine the effect of wood moisture content on fungal growth and wood colouration (melanisation).
Five replicate trials were set up using increment cores (10mm diameter) which were taken from bark to pith of freshly-felled Pinus radiata logs. Increment cores were pre-conditioned to different moisture content levels (< 30%, 50-70%, 120-140% and > 200%) using silica gel. After pre-conditioning, cores were individually encapsulated in wax and aseptically infected with Sphaeropsis sapinea introduced onto the outer (bark), freshly exposed (wax removed) cross-cut end. Sets of inoculated increment cores were incubated at 25°C. In the first trial, sets of incubated cores were assessed at two, six and nine days by cutting replicate cores into serial 3-mm-thick disks which were then plated on malt agar media. Four other replicate trials were assessed after nine days incubation following the procedure just described. Fungal growth on media was taken as a measure to determine depth of radial penetration (colonisation) at each wood moisture content level used. Also, melanisation was visually estimated along the core length. No apparent relationship was found between wood moisture content and ability of S. sapinea to colonise and melanise radiata pine.