In vitro screening of Latvian isolates of Bjerkandera adusta and Sistotrema brinkmannii as potential biocontrol agents against Heterobasidion root and butt rots

Root and butt rots caused by Heterobasidion spp. are destructive diseases of conifer forest stands that may be controlled by spraying freshly cut stumps with chemical or biological treatments, including the effective and widely used biological control agent Phlebiopsis gigantea. In this study, we tested in vitro different Latvian isolates of the fungal species Bjerkandera adusta and Sistotrema brinkmannii for their antagonistic activity against both Heterobasidion species present in Northern Europe and Baltic countries, namely H. annosum and H. parviporum, using Latvian isolates of P. gigantea and the Rotstop (R) strain as controls. The growth rate of isolates on agar media and their ability to produce oidia or conidia were also assessed. In general, B. adusta performed better than S. brinkmannii. Some isolates of B. adusta ranked similarly to those of P. gigantea in terms of oidia production, growth rate and ability to overgrow the mycelium of both H. annosum and H. parviporum. These isolates will be further tested in field conditions.