Decay of the water reed Phragmites communis caused by the white-rot fungus Phlebia tremellosa and the influence of some environmental factors.

The strain Phlebia tremellosa SBUG 1630 isolated from a thatched roof in Northern Germany is capable of colonizing and degrading effectively the water reed Phragmites communis. Within 96 h after inoculation, mycelia covered both the outer and the inner surface of reed shoot fragments as observed by scanning electron microscopy. Interestingly, top culm sections and culm edges were particularly susceptible towards fungal degradation. The weight loss of culms reached 20-73% depending on the environmental conditions applied during the incubation of 70 days. Reed degradation was stable at pH 4 to pH 8 and optimal between 25 and 30 °C. Short-term incubation at elevated temperatures (37 to 55 °C) affected the fungal reed degradation to only a minor extent, whereas > 18 h at 55 °C completely inhibited fungal growth and reed degradation. Supplementation with 43 mM NH4Cl enhanced the reed degradation up to 9%. In contrast, the addition of diammonium tartrate increased the weight loss of the samples considerably up to 16% at 344 mM. Furthermore, reed degradation by P. tremellosa was increased by supplementing the test medium with Mn (99 to 1584 μM), Cu (150 to 300 μM), and less significantly phosphate (4 mM), Zn (37 to 74 μM), and Ag (76 μM) after 70 days. In addition, activities of the ligninolytic enzymes laccase (max. 27.4 nmol ml-1 min-1) and lignin peroxidase (max. 22.8 nmol ml-1 min-1) were rather low in nitrogen-limited medium, whereas considerably higher levels of manganese peroxidase (max. 635.9 nmol ml-1 min-1) were observed.