Epsilon Archive for Student Projects

Abstract

Chaga has become more popular in recent years as a beneficial natural supplement and wellness tea.
Understanding chaga source limitations and its harvest dynamics as well as it’s potential revenue
streams would be important for future chaga growers in Sweden. Under natural conditions, the
fungus Inonotus obliquus takes many years to establish and develop sterile conks that are then able
to be harvested. Cultivating the fungus in forests for profitability therefore would be best optimized
by choosing isolates that can establish more quickly. In this study, the growth of I. obliquus was
analysed from 10 samples collected across a climatic gradient in Sweden, on three different nutrient
media and at three different temperatures, in order to select superior isolates that can be used for
cultivation and under optimal conditions for mass inoculum production. The results showed
significantly higher mycelium growth on yeast agar (YA) and potato dextrose agar (PDA), compared
to birch agar (BA). No significant difference was found in growth rates between samples originating
from the North (64° North) and the South (56° North) of Sweden. Highest growth rate occurred at
16°C, followed by 20°C and finally 26°C and this was consistent across all three media tested. In
addition to the in vitro growth trials, the degree of pigmentation was assessed in each culture, as
pigmentation is commonly an indicator of the presence of melanins which are known bioactive
secondary metabolites. Results showed that the fungus growth on PDA and YA exhibited more
pigmentation than BA. Interestingly the isolate showing highest growth (S4) showed least
pigmentation, and conversely the isolate showing least growth (S3) produced the highest number of
highly pigmented petri plates. This may indicate a potential trade-off between primary and
secondary metabolite production and ought to be investigated in more detail in future growth
optimisation experiments. From the results we recommend future in vitro cultivation of chaga
Inonotus obliquus in YA at least as low as 16°C. Further in vitro optimisation experiments could
investigate lower temperatures to find the optimal growing temperature.