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Scientists unlock the genome of the only biocontrol fungus (Phlebiopsis gigantea) commonly used against the conifer root and butt rot pathogen

The genome of the biological control agent Phlebiopsis gigantea commonly used against the root and butt rot pathogen (Heterobasidion annosum) has been sequenced. Heterobasidion annosum (Fr.) Bref. is the main cause of root and butt rot in conifer forests in the northern hemisphere. Protection measures against Heterobasidion spp. have been focused on preventing germination and growth of the fungi after spore deposition. Over the last 50 years a large number of commercially produced compounds have been tested as stump protectants. Of these, urea and borates have been shown to be the most effective against Heterobasidion spp. and are used commercially.

In spite of their effectiveness, there have been increased objections against the use of commercially produced compounds, for both practical and environmental reasons.  Biocontrol has been proposed as an alternative to the chemical control, only P. gigantea (Fr.) Jül is currently used and with very good results. Phlebiopsis gigantea is common on conifer stumps in boreal and temperate forests. As a primary colonizer of conifer logs, it gradually causes a significant decay on such material. In 1952, John Rishbeth from Great Britain was the first to discover that P. gigantea was able to replace Heterobasidion spp. on conifer (pine) stumps and proposed the use of the fungus as a biocontrol agent. Phlebiopsis gigantea is now commercially produced and marketed in Scandinavia, as a biocontrol product (Rotstop®, manufactured by Verdera). It is also commercially available in Poland and Great Britain as PG IBL® and PG Suspension®, respectively.

Scientists, however, have now a better grasp on this most effective and the only biocontrol agent against the conifer tree pathogen as its entire genome has been sequenced in a multi-year research project. The results of the project were published in the journal PLOS Genetics”(see PLOS Genetics 10(12): e1004759;  doi:10.1371/journal.pgen.1004759). The project which was co-ordinated by the USDA Forest Products Laboratory, Madison, USA involved 39 fungi researchers from around the world, including Professor of Forest Pathology Fred Asiegbu, University researcher (Dr. Andriy Kovalchuk) and postdoc scientist (Dr. Anthnony Mgbeahuruike) from the University of Helsinki.  According to Professor Asiegbu, “availability of the genome sequence of this fungus opens up an opportunity for a better understanding of how the fungus is able to  tolerate and utilize resinous extractives (e.g., resin acids, triglycerides, long chain fatty acids) thus making it an efficient colonizer of freshly cut conifer woods. It is this unusual capability that also led to the development of Phlebiopsis gigantea as an effective biocontrol agent.

Professor Asiegbu believes that the availability of the genome sequence will additionally  contribute to a fundamental understanding of conifer wood colonization by decay fungus as well as carbon cycling processes.

Contact: Prof. Fred Asiegbu (e-mail: Fred.Asiegbu; Tel: 02941 58109/050-4486139).

Pictured: Heterobasidion annosum (right) and Phlebiopsis gigantea (left).

Text and image: Fred Asiegbu