Influence of the Heterobasidion annosum (Fr.) Bref. mycelium on Paulownia COTE-2 wood in vitro

Paulownia is one of the fastest growing trees in the world. This species appears more and more often in plantations of trees in Poland. However, there is a potential threat to the success of the plantation, i.e. root pathogens including Heterobasidion annosum. The aim of the study was to test the ability of two strains of H. annosum to decompose paulownia wood in laboratory conditions. Pure mycelial cultures (Ha9X320 and Ha2003 strains) for the research came from the culture collection of the Department of Forest Phytopathology at the University of Life Sciences in Poznan, while the wood of Paulownia COTE-2 was obtained from plantations in the Granada region, Spain. Before experiments, wood samples (20x20x30 mm) were autoclaved twice on consecutive days at 121 degrees C (for 20 min on the first day and 10 min on the other one). Following sterilization, the samples were left for several hours to cool down. Then, they were soaked for an hour in cool sterile distilled water to increase their initial moisture content. Two paulownia wood samples were placed in each of 40 Kolle flasks containing 2-week-old H. annosum mycelium cultured on 30 mL of MEA medium. After 60 days samples were removed from the half of flasks, cleaned of the mycelium growing on them, and then dried at 105 degrees C until absolutely dry. After 120 days, the remaining samples were removed from the flasks. The percent loss of wood weight was calculated by comparing the initial and final absolute dry weight of the samples. Wood of Paulownia COTE-2 shows considerable resistance to decomposition caused by the mycelium of H. annosum in laboratory conditions. The tested strains of H. annosum after 120 days of the experiment caused a slight weight loss of the wood samples (on average by 0.56% for two strains). There were no statistical differences between the strains used in the study.